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1. Ultrafine Grain 316L Stainless Steel Manufactured by Ball Milling and Spark Plasma Sintering: Consequences on the Corrosion Resistance in Chloride Media

Author

Eric Hug, Clément Keller, Cendrine Folton, Jade Papin, Kostiantyn Tabalaiev, and Gaël Marnier

Subjects
corrosion, passivity, pitting, grain size, 316L, SPS, Mining engineering. Metallurgy, TN1-997
Abstract

This paper reports experimental results concerning the corrosion of 316L austenitic stainless steels produced by ball milling and spark plasma sintering in NaCl electrolyte. Specimens with grain sizes ranging from 0.3 µm to 3 µm, without crystallographic texture, were obtained and compared with a cast that is 110 µm in grain size and an annealed reference. The potentiodynamic experiments showed that the reduction in grain size leads to a degradation of the electrochemical passivation behavior. This detrimental effect can be overcome by appropriate passivation in a HNO3 concentrated solution before consolidation. The Mott–Schottky measurements showed that the semiconducting properties of the passive layer do not vary significantly on the grain size, especially the donor density, which is responsible for the chemical passivation breakdown by chloride anions. The total electrical resistance of the layer, measured by impedance spectroscopy is always lower than the one of a cast and annealed 316L, but it slightly increases with a reduction in grain size in the ultrafine grain range. This is followed by a slight increase in the thickness of the oxide layer. The effect of chloride ions is very pronounced in terms of passivation breakdown if the powder is not passivated prior to sintering. This leads to the nucleation and growth of subsurface main pits and the formation of secondary satellite pits, especially for the smallest grain sizes. Passivation of the 316L powder before sintering has been found to be an effective way to prevent this phenomenon.

Published
2024
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2. Size effects in cobalt plastically strained in tension: impact on gliding and twinning work hardening mechanisms

Author

Eric Hug, Clément Keller, Pierre-Antoine Dubos, and Mayerling Martinez Celis

Subjects
Cobalt, Size effects, Mechanical properties, Dislocations, Basal slip mechanisms, Twinning, Mining engineering. Metallurgy, TN1-997
Abstract

Mechanical properties in tension of cobalt have been studied in a wide range of grain size d using thickness t of samples from 125 to 700 μm. The Hall and Petch (HP) relationship indicates that the yield stress strongly varies for t/d below a critical value around 14, highlighting the existence of a multicrystalline regime. The behavior becomes almost single crystalline when t/d is lower than 2.5, with a very small HP slope. The reduction of the t/d ratio has also a large influence on the work hardening of cobalt, especially in the beginning of plasticity, which mainly corresponds to the stage of basal slip mechanisms. However, these size effects tend to vanish when twinning becomes predominant. Nanoindentation measurements and application of a simple composite model show that the appearance of the multicrystalline regime is closely related to surface effects that develop through the thickness of the specimens. In addition, the Kocks - Mecking work hardening model predicts a significant increase of the average free path of dislocations in the basal slip stage. A quantitative analysis of dislocation pile-ups that develop during this stage supports the hypothesis that the mechanical softening observed in cobalt multicrystal is related to a higher activity of dislocations, which can escape more easily on free surfaces. When twinning becomes the main deformation mechanism, dislocation glide is restricted which reduced, in turn, the surface effect. Consequently, size effects gradually disappear with hardening.

Published
2021
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3. Experimental and Finite Element Analysis of the Tensile Behavior of Architectured Cu-Al Composite Wires

Author

Alireza Dashti, Clément Keller, Benoit Vieille, Alain Guillet, and Christophe Bouvet

Subjects
wire drawing, Cu-Al composite wires, finite element analysis, Technology, Electrical engineering. Electronics. Nuclear engineering, TK1-9971, Engineering (General). Civil engineering (General), TA1-2040, Microscopy, QH201-278.5, Descriptive and experimental mechanics, QC120-168.85
Abstract

The present study investigates, experimentally and numerically, the tensile behavior of copper-clad aluminum composite wires. Two fiber-matrix configurations, the conventional Al-core/Cu-case and a so-called architectured wire with a continuous copper network across the cross-section, were considered. Two different fiber arrangements with 61 or 22 aluminum fibers were employed for the architectured samples. Experimentally, tensile tests on the two types of composites show that the flow stress of architectured configurations is markedly higher than that of the linear rule of mixtures’ prediction. Transverse stress components and processing-induced residual stresses are then studied via numerical simulations to assess their potential effect on this enhanced strength. A set of elastic-domain and elastoplastic simulations were performed to account for the influence of Young’s modulus and volume fraction of each phase on the magnitude of transverse stresses and how theses stresses contribute to the axial stress-strain behavior. Besides, residual stress fields of different magnitude with literature-based distributions expected for cold-drawn wires were defined. The findings suggest that the improved yield strength of architectured Cu-Al wires cannot be attributed to the weak transverse stresses developed during tensile testing, while there are compelling implications regarding the strengthening effect originating from the residual stress profile. Finally, the results are discussed and concluded with a focus on the role of architecture and residual stresses.

Published
2021
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4. Exploring the Strain Hardening Mechanisms of Ultrafine Grained Nickel Processed by Spark Plasma Sintering

Author

Lucía García de la Cruz, Mayerling Martinez Celis, Clément Keller, and Eric Hug

Subjects
nickel, spark plasma sintering, ultrafine grained microstructure, plasticity mechanisms, deformed state, dislocation structures, Mining engineering. Metallurgy, TN1-997
Abstract

Ultrafine grained (UFG) materials in the bigger grain size range (0.5–1) µm display a good combination of strength and ductility, unlike smaller size UFG and nanostructured metals, which usually exhibit high strength but low ductility. Such difference can be attributed to a change in plasticity mechanisms that modifies their strain hardening capability. The purpose of this work is to investigate the work hardening mechanisms of UFG nickel considering samples with grain sizes ranging from 0.82 to 25 µm. Specimens processed combining ball milling and spark plasma sintering were subjected to monotonous tensile testing up to fracture. Then, microstructural observations of the deformed state of the samples were carried out by electron backscattered diffraction and transmission electron microscopy. A lower strain hardening capability is observed with decreasing grain size. Samples in the submicrometric range display the three characteristic stages of strain hardening with a short second stage and the third stage beginning soon after yielding. Microstructural observations display a low fraction of low angle grain boundaries and dislocation density for the sample with d = 0.82 µm, suggesting changes in plasticity mechanisms early in the UFG range.

Published
2020
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5. A Characterization of the Damage Process under Buckling Load in Composite Reinforced by Flax Fibres

Author

Meriem Fehri, Alexandre Vivet, Fakhreddine Dammak, Mohamed Haddar, and Clément Keller

Subjects
composites, flax fibres, buckling test, acoustic emission, damage process, Technology, Science
Abstract

The purpose of this work is to analyze the damage process resulting from buckling load applied on composites reinforced by flax fibre. Continous buckling test was performed on specimens until cracks appeared on their outer face. This test was monitored with an acoustic emission system. The high sensitivity of this method allows the detection of any process or mechanism generating sound waves. Moreover, this technic has the advantage of not causing contact in the deformed zone and thus to overcome the parasitic damage that may result from the stress concentrations in these areas. A multiparametric analysis is used to identify the acoustic signatures corresponding to each damage mechanism involved in the materials, and then follow their evolution in order to identify the most critical mechanisms leading to the final breakage of the material. The presence of these damage mechanisms was confirmed post-test by microscopic observations. Three orientations of laminate specimens (0°, 90° and 45°), relative to flax fabric architecture, were tested in order to characterize and highlight on their own damage process. Similarities as differences were observed between these mechanisms. We have deduced that the high porosity rate found in our composites are resulting from manufacturing parameters. Architecture and properties of the flax fabric influenced negatively the mechanical properties later by accentuating the gap between theoretical and practical values (17% to 22.4%) and by accelerating the development of certain damages such as matrix cracking which acoustic hit density is superior to 70% and fiber/matrix decohesion which occurs very early.

Published
2020
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6. A Novel Geometry for Shear Test Using Axial Tensile Setup

Author

Sibo Yuan, Laurent Duchêne, Olivier Milis, Clément Keller, Eric Hug, and Anne-Marie Habraken

Subjects
in-plane shear, thin specimen, finite element simulation, General Works
Abstract

This paper studies a novel geometry for the in-plane shear test performed with an axial electromechanical testing machine. In order to investigate the influence of the triaxiality rate on the mechanical behavior, different tests will be performed on the studied material: simple tensile tests, large tensile tests and shear tests. For the whole campaign, a common equipment should be employed to minimize the impact of the testing device. As a consequence, for the shear tests, the geometry of the specimen must be carefully designed in order to adapt the force value and make it comparable to the one obtained for the tensile tests. Like most of the existing shear-included tensile test specimens, the axial loading is converted to shear loading at a particular region through the effect of geometry. A symmetric shape is generally preferred, since it can restrict the in-plane rotation of the shear section, keep shear increasing in a more monotonic path and double the force level thanks to the two shear zones. Due to the specific experimental conditions, such as dimensions of the furnace and the clamping system, the position of the extensometer or the restriction of sheet thickness (related to the further studies of size effect at mesoscale and hot temperature), several geometries were brought up and evaluated in an iterative procedure via finite element simulations. Both the numerical and experimental results reveal that the final geometry ensures some advantages. For instance, a relatively low triaxiality in the shear zone, limited in-plane rotation and no necking are observed. Moreover, it also prevents any out-of-plane displacement of the specimen which seems to be highly sensitive to the geometry, and presents a very limited influence of the material and the thickness.

Published
2018
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7. Impact of hardening law on the FEM prediction of residual stresses in copper-clad aluminum wires

Author

Alireza Dashti, Clément Keller, Benoit Vieille, Alain Guillet, Calogero Gallo, Anne-Marie Habraken, Laurent Duchêne, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Génie de Production (LGP), Ecole Nationale d'Ingénieurs de Tarbes (ENIT), Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT), and Université de Liège

Subjects
Wire drawing, Control and Systems Engineering, Mechanical Engineering, Aluminium, Finite element analysis, Isotropic-kinematic hardening, Bimetallic composite, Copper, Industrial and Manufacturing Engineering, Software, [SPI.MAT]Engineering Sciences [physics]/Materials, Computer Science Applications
Abstract

International audience; Near-surface axial tensile residual stresses (from manufacturing) are reportedly detrimental to the yield strength of cold-drawn wires. Therefore, a reliable evaluation of their magnitude is necessary. The size and geometry of electrical wires can pose challenges for experimental measurement of those residual stresses. For that reason, the finite element analysis can prove useful. However, great care must be taken with the right choice of strain hardening law for a sound assessment of residual stresses. Given the complex loading condition during cold drawing, cyclic loading arises through the wire cross section even in single-pass drawing. As a result, it is of crucial importance to account for associated backstresses. The current study makes a comparison between two different hardening laws’ prediction of axial residual stress profiles in numerically cold-drawn Cu–Al composite wires of various Al volume fractions. The impact of die geometry on this prediction was also examined for a 25%Al-wire. To that end, a combined isotropic-kinematic law and a pure isotropic constitutive equation were considered. The results imply a possible overestimation of residual stresses by the pure isotropic model at relatively low Al volume fractions. The difference between the maximum magnitudes of tensile or compressive residual stresses (predicted by the two models) could be as large as about 100 MPa (larger than the yield strength of the starting materials). Furthermore, the tooling geometry minimally affects the prediction of the hardening models. In conclusion, backstresses are not to be overlooked for accurate estimations of drawing residual stresses at low Al volume fractions.

Published
2023

8. Combined effect of a spread powder particle size distribution, surface machining and stress-relief heat treatment on microstructure, tensile and fatigue properties of 316L steel manufactured by laser powder bed fusion

Author

Josiane Nguejio, Morgane Mokhtari, Elie Paccou, Eric Baustert, Leila Khalij, Eric Hug, Pierre Bernard, Sébastien Boileau, Clément Keller, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Génie de Production (LGP), Ecole Nationale d'Ingénieurs de Tarbes (ENIT), Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT), Volum-e, Laboratoire de Mécanique de Normandie (LMN), Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), ArianeGroup, CRT Analyses Et Surfaces, and Ce travail est lié au projet CLIP-FAM financé par la région Normandie

Subjects
[PHYS]Physics [physics], heat treatment, Mechanical Engineering, powder characteristics, microstructure, [SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph], Industrial and Manufacturing Engineering, Computer Science Applications, Control and Systems Engineering, Laser Powder Bed Fusion, fatigue, stainless steel, Software, machining
Abstract

International audience; Additive Manufacturing is a powerful process to build complex geometry. Besides the numerous process parameters influencing the mechanical part performances, others parameters related to the initial powder feedstock or component machining are of most importance. In this study, the combined effect of a wide particle size distribution, surface machining and stress-relief heat treatment on the microstructure and mechanical properties (tension and fatigue) of a stainless steel AISI 316L, produced by laser powder bed fusion, is investigated. In order to correctly investigate those parameters separately, the netshape/machined character of the sample, alongside with the heat treatment is studied for two kinds of powder having different particle size distributions, i.e, narrow and widely spread. Results show that a large spread of particle size is only slightly detrimental to the fatigue life, in particular in high cycle conditions due to a larger porosity related to a weakly more uneven particle spatial distribution in the bed. Nevertheless, this effect is of a second order compared to machining or heat treatments which greatly affect the mechanical behaviour. Surface machining and moderate heat treatment are then the best post-operational steps to increase the fatigue life in high cycle fatigue conditions independently of the particle size distribution. Results are discussed in terms of defects, microstructural modifications, surface roughness, martensitic transformation and mechanical loading.

Published
2023

10. Impact of hardening law on the FEM prediction of residual stresses in Cu-Al wires

Author

Alireza Dashti, Clément Keller, Benoit Vieille, Alain Guillet, Calogero Gallo, Anne-Marie Habraken, and Laurent Duchêne

Abstract

Near-surface axial tensile residual stresses (from manufacturing) are reportedly detrimental to the yield strength of cold-drawn wires. Therefore, a reliable evaluation of their magnitude is necessary. The size and geometry of electrical wires can pose challenges for experimental measurement of those residual stresses. For that reason, the finite element analysis can prove useful. However, great care must be taken with the right choice of strain hardening law for a sound assessment of residual stresses. Given the complex loading condition during cold drawing, cyclic loading arises through the wire cross section even in single-pass drawing. As a result, it is of crucial importance to account for associated backstresses. The current study makes a comparison between two different hardening laws’ prediction of axial residual stress profiles in numerically cold-drawn Cu-Al composite wires of various Al volume fractions. The impact of die geometry on this prediction was also examined for a 25%Al-wire. To that end, a combined isotropic-kinematic law and a pure isotropic constitutive equation were considered. The results imply a possible overestimation of residual stresses by the pure isotropic model at relatively low Al volume fractions. The difference between the maximum magnitudes of tensile or compressive residual stresses (predicted by the two models) could be as large as about 100 MPa (larger than the yield strength of the starting materials). Furthermore, the tooling geometry minimally affects the prediction of the hardening models. In conclusion, backstresses are not to be overlooked for accurate estimations of drawing residual stresses at low Al volume fractions.

Published
2022

12. Metal Forming-Induced Residual Stresses and Rule of Mixtures’ Prediction of Tensile Behavior of Bimetallic Wires

Author

Alireza Dashti, Alain Guillet, Clément Keller, Benoit Vieille, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Génie de Production (LGP), Ecole Nationale d'Ingénieurs de Tarbes (ENIT), Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National Polytechnique (Toulouse) (Toulouse INP), and Université de Toulouse (UT)-Université de Toulouse (UT)

Subjects
Wire drawing, Mechanics of Materials, Mechanical Engineering, Iron, Aluminium, Finite element analysis, General Materials Science, Bimetallic composites, Copper, [SPI.MAT]Engineering Sciences [physics]/Materials
Abstract

International audience; The present study investigates the tensile behavior of the two bimetallic composite wires Cu-Al and Fe-Al. The purpose is to understand the deviation their tensile strengths show from the Rule of Mixtures’ prediction. To that end, an experimental-numerical approach was adopted. Following tensile testing of the above cold-drawn composite wires, the manufacturing process (wire drawing) was simulated via finite element analysis. The prominent role of processing-induced residual stresses on the yield strength of cold-drawn products is known. Therefore, a discussion based on the axial tensile residual stress profile was developed. It was concluded that the higher-magnitude-near-surface tensile residual stresses in the Fe-Al wire causes its tensile curve to show a negative deviation from the Rule of Mixtures (RoM). The Cu-Al wire, on the contrary, exhibits a slight positive deviation.

Published
2022

13. Novel approach to optimize the mechanical properties of Cu-Al composite wires

Author

Alireza Dashti, Clément Keller, Benoit Vieille, Alain Guillet, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Ecole Nationale d'Ingénieurs de Tarbes (ENIT), Institut National Polytechnique (Toulouse) (Toulouse INP), and Université de Toulouse (UT)-Université de Toulouse (UT)

Subjects
[SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], General Materials Science, [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], [SPI.MAT]Engineering Sciences [physics]/Materials
Abstract

International audience

Published
2022

14. Size effects in cobalt plastically strained in tension: impact on gliding and twinning work hardening mechanisms

Author

Pierre-Antoine Dubos, Eric Hug, Clément Keller, Mayerling Martinez Celis, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Institut de Recherche en Génie Civil et Mécanique (GeM), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-École Centrale de Nantes (ECN)-Centre National de la Recherche Scientifique (CNRS), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
lcsh:TN1-997, Size effects, Basal slip mechanisms, Twinning, Materials science, Dislocations, Mechanical properties, 02 engineering and technology, Slip (materials science), Work hardening, Plasticity, 01 natural sciences, Biomaterials, 0103 physical sciences, Composite material, lcsh:Mining engineering. Metallurgy, ComputingMilieux_MISCELLANEOUS, [PHYS]Physics [physics], 010302 applied physics, Metals and Alloys, Cobalt, 021001 nanoscience & nanotechnology, Grain size, Surfaces, Coatings and Films, Deformation mechanism, Ceramics and Composites, Hardening (metallurgy), Dislocation, 0210 nano-technology, Crystal twinning
Abstract

International audience; Mechanical properties in tension of cobalt have been studied in a wide range of grain size d using thickness t of samples from 125 to 700 μm. The Hall and Petch (HP) relationship indicates that the yield stress strongly varies for t/d below a critical value around 14, highlighting the existence of a multicrystalline regime. The behavior becomes almost single crystalline when t/d is lower than 2.5, with a very small HP slope. The reduction of the t/d ratio has also a large influence on the work hardening of cobalt, especially in the beginning of plasticity, which mainly corresponds to the stage of basal slip mechanisms. However, these size effects tend to vanish when twinning becomes predominant. Nanoindentation measurements and application of a simple composite model show that the appearance of the multicrystalline regime is closely related to surface effects that develop through the thickness of the specimens. In addition, the Kocks - Mecking work hardening model predicts a significant increase of the average free path of dislocations in the basal slip stage. A quantitative analysis of dislocation pile-ups that develop during this stage supports the hypothesis that the mechanical softening observed in cobalt multicrystal is related to a higher activity of dislocations, which can escape more easily on free surfaces. When twinning becomes the main deformation mechanism, dislocation glide is restricted which reduced, in turn, the surface effect. Consequently, size effects gradually disappear with hardening.

Published
2021

15. Study by nanoindentation of the influence of the manufacturing process on the mechanical properties of Copper-Clad Aluminum wires

Author

Sophie Eve, Clément Keller, Éric Hug, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SPI]Engineering Sciences [physics], Architecture, Intermetallic compounds, General Materials Science, Copper-aluminum bimetallic wires, Nanoindentation
Abstract

International audience; We studied the influence of the architecture of Copper-Clad Aluminum (CCA) wires produced by cold-drawing process, on the mechanical properties of materials, and the development of intermetallic compounds at the interface after annealing. Simple and architectured-CCA (A_CCA) rods, fabricated by stacking and re-drawing of original CCA wires, have been characterized before and after a thermal treatment. Nanoindentation tests, performed to map the hardness and the elastic modulus at the microscale, allow to well catch the recrystallization phenomenon, which takes place in both the Cu and the Al subjected to severe plastic deformation, as well as the formation of three intermetallic compounds (IMC) at the interface. Our measures underline that the mechanical properties of all the components involved in the wires, i.e., Cu, Al, and eventually the IMC developing after annealing, are only slightly influenced by the structuration of the wires. IMC developing at the Cu/Al interfaces present a high hardness, and might deteriorate the mechanical properties of the wires, even more for A_CCA wires, which exhibit more interfaces that the traditional CCA samples.

Published
2022

16. Investigations of powder reusing on microstructure and mechanical properties of Inconel 718 obtained by additive manufacturing

Author

Josiane Nguejio, Elie Paccou, Eric Bauster, Morgane Mokhtari, Williams Lefebvre, S. Boileau, Xavier Sauvage, P. Babillot, Clément Keller, Pierre Bernard, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Ecole Nationale d'Ingénieurs de Tarbes (ENIT), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU), Université de Rouen Normandie (UNIROUEN), ArianeGroup, Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Génie de Production (LGP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT), CRT Analyses Et Surfaces, and Volum-e

Subjects
010302 applied physics, Reusability, Fusion, Materials science, Additive manufacturing, Mechanical Engineering, Metallurgy, 02 engineering and technology, Reuse, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Microstructure, 01 natural sciences, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], Mechanics of Materials, 0103 physical sciences, Powder bed, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Mechanical Properties, General Materials Science, 0210 nano-technology, Inconel, Nickel Based Superalloy, ComputingMilieux_MISCELLANEOUS
Abstract

International audience; Laser powder bed fusion, largely employed for additive manufacturing, induces after each batch a large quantity of remaining powder. This study focuses on the possibility to reuse this remaining powder after a large number of production cycles and on the influence of such reusing on the microstructure and mechanical properties. Inconel 718 parts made from fresh and 50 times reused powder were processed and then characterized in the asbuilt state. The effect of powder reuse on the microstructure was assessed thanks to a multiscale study and the resulting mechanical response was evaluated using both monotonous and cyclic tests. Our results clearly show that despite a better powder flowability for the reused powder, only minor differences between the two investigated materials demonstrating the possibility of high-quality parts production from reused powders.

Published
2021

17. Accounting for Size Dependence on the meso- or on the Micro-scale in Polycrystalline Plasticity. A Comparative Study for Different Grain Size Distributions

Author

Clément Keller, Fabrice Barbe, Mathieu Calvat, Baptiste Flipon, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Centre de Mise en Forme des Matériaux (CEMEF), Mines Paris - PSL (École nationale supérieure des mines de Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Dependency (UML), Scale (ratio), 02 engineering and technology, Plasticity, [PHYS.MECA.MSMECA]Physics [physics]/Mechanics [physics]/Materials and structures in mechanics [physics.class-ph], 01 natural sciences, Grain size, 010101 applied mathematics, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], 020303 mechanical engineering & transports, 0203 mechanical engineering, Critical resolved shear stress, Particle-size distribution, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Grain boundary, Statistical physics, Crystallite, 0101 mathematics, ComputingMilieux_MISCELLANEOUS
Abstract

This paper presents a full-field analysis of size dependent crystal plasticity according to two robust and efficient ways to account for microstructural internal length effects in the constitutive laws. Both consist in introducing a Hall–Petch term in the definition of the resolved shear stress. They differ by the nature of the internal length and thus, intrinsically, on the scale at which this size dependency is introduced. In the meso-scale approach, it is directly the size of the considered grain. In the micro-scale approach, it is the distance to the grain boundary. Analyses show that meso- and micro-scale differences increase as the grain size distribution evolves from a unimodal to a bimodal one.

Published
2021

18. Elaboration of Architectured Copper Clad Aluminium Composites by a Multi-Step Drawing Process

Author

F. Moisy, Mayerling Martinez, Eric Hug, Antoine Gueydan, Alain Guillet, Xavier Sauvage, Clément Keller, and Nga Nguyen

Subjects
010302 applied physics, Materials science, Mechanical Engineering, chemistry.chemical_element, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Copper, chemistry, Mechanics of Materials, Aluminium, Scientific method, 0103 physical sciences, General Materials Science, Composite material, 0210 nano-technology, Elaboration
Abstract

Architectured copper clad aluminium composites processed by a restacking drawing method at room temperature are reported in this work. Wires were drawn to severe plastic strain without any intermediate annealing. Three different diameters were studied in order to examine the influence of a different plastic deformation level on the structure of the different wires. Thanks to image processing it has been shown that independently of the plastic deformation, inserted fibers remain continuous and are homogeneous in size and shape. Furthermore, XRD and TEM characterizations confirm that there is no significant intermetallic growth during the deformation. Thus, the improvement and/or degradation of the functional properties of the wires can be well controlled by performing an appropriate post-processing annealing treatment. Keywords: Cu/Al composite, architectured wire, drawing, microscopy, image processing

Published
2018

19. Exploring the Strain Hardening Mechanisms of Ultrafine Grained Nickel Processed by Spark Plasma Sintering

Author

Clément Keller, Eric Hug, Mayerling Martinez Celis, Lucía García de la Cruz, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
lcsh:TN1-997, plasticity mechanisms, Materials science, deformed state, Spark plasma sintering, 02 engineering and technology, Work hardening, Plasticity, 01 natural sciences, nickel, ultrafine grained microstructure, 0103 physical sciences, General Materials Science, Composite material, Ductility, lcsh:Mining engineering. Metallurgy, ComputingMilieux_MISCELLANEOUS, Tensile testing, 010302 applied physics, [PHYS]Physics [physics], dislocation structures, Metals and Alloys, Strain hardening exponent, 021001 nanoscience & nanotechnology, Grain size, Grain boundary, 0210 nano-technology, spark plasma sintering
Abstract

Ultrafine grained (UFG) materials in the bigger grain size range (0.5&ndash, 1) &micro, m display a good combination of strength and ductility, unlike smaller size UFG and nanostructured metals, which usually exhibit high strength but low ductility. Such difference can be attributed to a change in plasticity mechanisms that modifies their strain hardening capability. The purpose of this work is to investigate the work hardening mechanisms of UFG nickel considering samples with grain sizes ranging from 0.82 to 25 &micro, m. Specimens processed combining ball milling and spark plasma sintering were subjected to monotonous tensile testing up to fracture. Then, microstructural observations of the deformed state of the samples were carried out by electron backscattered diffraction and transmission electron microscopy. A lower strain hardening capability is observed with decreasing grain size. Samples in the submicrometric range display the three characteristic stages of strain hardening with a short second stage and the third stage beginning soon after yielding. Microstructural observations display a low fraction of low angle grain boundaries and dislocation density for the sample with d = 0.82 &micro, m, suggesting changes in plasticity mechanisms early in the UFG range.

Published
2021

20. Influence of a rescanning strategy with different laser powers on the microstructure and mechanical properties of Hastelloy X elaborated by powder bed fusion

Author

H. Briatta, Benoit Vieille, M. Mokhtari, Clément Keller, P. Bernard, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), ArianeGroup, Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), and Normandie Université (NU)

Subjects
[PHYS]Physics [physics], 0209 industrial biotechnology, Materials science, Laser scanning, Mechanical Engineering, 02 engineering and technology, [PHYS.MECA.MSMECA]Physics [physics]/Mechanics [physics]/Materials and structures in mechanics [physics.class-ph], 021001 nanoscience & nanotechnology, Condensed Matter Physics, Microstructure, Laser, law.invention, 020901 industrial engineering & automation, Mechanics of Materials, law, Ultimate tensile strength, General Materials Science, Texture (crystalline), Laser power scaling, Composite material, 0210 nano-technology, Ductility, Lasing threshold, ComputingMilieux_MISCELLANEOUS
Abstract

The present study investigates the influence of a rescanning strategy on the microstructure and mechanical properties of Hastelloy X samples manufactured by laser powder bed fusion process in additive manufacturing. After a first lasing leading to powder melting, a second lasing is performed on the solid metal with five considered laser powers corresponding to 100-80-60-40 and 20% of the power of the first laser scan. The microstructure and mechanical properties of the samples obtained from these elaboration strategies were then compared to those of a conventional strategy with and without heat treatment. Using electron microscopy, monotonic and loading/unloading tensile tests, the results revealed that samples elaborated with the rescanning strategy are characterized by weaker crystallographic texture, lower backstress and larger ductility compared to conventional elaboration parameters. However, these modifications induced by the second laser scan, depend on the second laser scanning power, better properties are observed for a decrease of 40% in the laser power during the second laser scan. Such strategy may be suitable to optimize the mechanical properties but also to potentially avoid post-elaboration heat treatments.

Published
2021

22. A Characterization of the Damage Process under Buckling Load in Composite Reinforced by Flax Fibres

Author

Clément Keller, Meriem Fehri, Alexandre Vivet, Mohamed Haddar, Fakhreddine Dammak, Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Unité de Génie de Production Mécanique et Matériaux - UGPM2 (Sfax, Tunisia), École Nationale d'Ingénieurs de Sfax | National School of Engineers of Sfax (ENIS), Unité Modélisation, Mécanique et Production (U2MP), Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN)

Subjects
Materials science, Composite number, 02 engineering and technology, flax fibres, 010402 general chemistry, composites, lcsh:Technology, 01 natural sciences, [SPI.MAT]Engineering Sciences [physics]/Materials, Breakage, Fiber, Composite material, lcsh:Science, Porosity, Engineering (miscellaneous), Stress concentration, damage process, lcsh:T, buckling test, [SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph], 021001 nanoscience & nanotechnology, 0104 chemical sciences, Characterization (materials science), Acoustic emission, Buckling, acoustic emission, Ceramics and Composites, lcsh:Q, 0210 nano-technology
Abstract

International audience; The purpose of this work is to analyze the damage process resulting from buckling load applied on composites reinforced by flax fibre. Continous buckling test was performed on specimens until cracks appeared on their outer face. This test was monitored with an acoustic emission system. The high sensitivity of this method allows the detection of any process or mechanism generating sound waves. Moreover, this technic has the advantage of not causing contact in the deformed zone and thus to overcome the parasitic damage that may result from the stress concentrations in these areas. A multiparametric analysis is used to identify the acoustic signatures corresponding to each damage mechanism involved in the materials, and then follow their evolution in order to identify the most critical mechanisms leading to the final breakage of the material. The presence of these damage mechanisms was confirmed post-test by microscopic observations. Three orientations of laminate specimens (0°, 90° and 45°), relative to flax fabric architecture, were tested in order to characterize and highlight on their own damage process. Similarities as differences were observed between these mechanisms. We have deduced that the high porosity rate found in our composites are resulting from manufacturing parameters. Architecture and properties of the flax fabric influenced negatively the mechanical properties later by accentuating the gap between theoretical and practical values (17% to 22.4%) and by accelerating the development of certain damages such as matrix cracking which acoustic hit density is superior to 70% and fiber/matrix decohesion which occurs very early.

Published
2020

23. Tunable surface boundary conditions in strain gradient crystal plasticity model

Author

Sibo Yuan, Anne Habraken, Laurent Duchene, Eric Hug, Clément Keller, Université de Liège, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Fonds National de la Recherche Scientifique [Bruxelles] (FNRS), ArGEnCo Department, MS2F Division (ArGEnCo), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), and Mechanics and Structures Department

Subjects
Surface (mathematics), Materials science, Constitutive equation, Finite elements, Dislocations, 02 engineering and technology, Plasticity, [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], [SPI.MAT]Engineering Sciences [physics]/Materials, Condensed Matter::Materials Science, 0203 mechanical engineering, [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], General Materials Science, Boundary value problem, Instrumentation, ComputingMilieux_MISCELLANEOUS, Boundary conditions, Strain gradient crystal plasticity, Mechanics, 021001 nanoscience & nanotechnology, 020303 mechanical engineering & transports, Surface effects, Mechanics of Materials, Free surface, Grain boundary, Dislocation, 0210 nano-technology, Single crystal
Abstract

International audience; The behavior of dislocations in the neighborhood of a metallurgical interface or a free surface can be totally different depending on the boundary conditions. Dislocations cease to move and accumulate around impermeable interfaces, such as grain boundaries or hard (i.e. coated or oxidized) external surfaces. On the contrary, dislocations annihilate on free surfaces, as supported by the image force concept. However the behavior of dislocations depends on the true surface permeability, which falls between these two idealized cases. In this paper, two different numerical methods are applied to model the intermediate surface behaviors: the virtual image geometrically necessary dislocation approach and the generalized elastic foundation approach while a strain gradient crystal plasticity constitutive law simulates the response of a Ni single crystal. It is demonstrated that a uniform dislocation density field on the surface can only be obtained by a variant of the generalized elastic foundation approach.

Published
2020

24. Elucidating the Effect of Bimodal Grain Size Distribution on Plasticity and Fracture Behavior of Polycrystalline Materials

Author

Vincenzo Gulizzi, Fabrice Barbe, Ivano Benedetti, Clément Keller, Mathieu Calvat, Barbe, Fabrice, Benedetti, Ivano, Gulizzi, Vincenzo, Calvat, Mathieu, Keller, Clément, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Università degli studi di Palermo - University of Palermo, Lawrence Berkeley National Laboratory [Berkeley] (LBNL), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, 02 engineering and technology, Plasticity, 021001 nanoscience & nanotechnology, 01 natural sciences, Polycrystalline material, Computer Science Applications, Crystal plasticity, 010101 applied mathematics, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], Modeling and Simulation, Particle-size distribution, Fracture (geology), Crystallite, 0101 mathematics, Elongation, Composite material, 0210 nano-technology, Settore ING-IND/04 - Costruzioni E Strutture Aerospaziali, Polycrystalline Materials, Bimodal Grain Size Distribution, Crystal Plasticity, Microcracking, Computational Micromechanics
Abstract

The refinement of grains in a polycrystalline material leads to an increase in strength but as a counterpart to a decrease in elongation to fracture. Different routes are proposed in the literature to try to overpass this strength-ductility dilemma, based on the combination of grains with highly contrasted sizes. In the simplest concept, coarse grains are used to provide relaxation locations for the highly stressed fine grains. In this work, a model bimodal polycrystalline system with a single coarse grain embedded in a matrix of fine grains is considered. Numerical full-field micro-mechanical analyses are performed to characterize the impact of this coarse grain on the stress-strain constitutive behavior of the polycrystal: the effect on plasticity is assessed by means of crystal plasticity finite element modeling [B. Flipon, C. Keller, L. Garcia de la Cruz, E. Hug and F. Barbe, Tensile properties of spark plasma sintered AISI 316L stainless steel with unimodal and bimodal grain size distributions, Mater. Sci. Eng. A 729 (2018) 248–256] while the effect on intergranular fracture behavior is studied by using boundary element modeling [I. Benedetti and V. Gulizzi, A grain-scale model for high-cycle fatigue degradation in polycrystalline materials, Int. J. Fract. 116 (2018) 90–105]. The analysis of the computational results, compared to the experimentally characterized tensile properties of a bimodal 316L stainless steel, suggests that the elasto-plastic interactions taking place prior to micro-cracking may play an important role in the mechanics of fracture of this steel.

Published
2020

25. A full-field crystal-plasticity analysis of bimodal polycrystals

Author

Clément Keller, Fabrice Barbe, Romain Quey, Baptiste Flipon, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Georges Friedel (LGF-ENSMSE), École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), and Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)

Subjects
Materials science, 02 engineering and technology, Spatial distribution, Crystal plasticity, 0203 mechanical engineering, General Materials Science, Full-field crystal plasticity, Stress concentration, Laguerre-Voronoi tessellations, Condensed matter physics, Bimodal microstructure, Applied Mathematics, Mechanical Engineering, Local scale, Grain size effect, Full field, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Grain size, 020303 mechanical engineering & transports, Mechanics of Materials, Modeling and Simulation, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology, Laguerre–Voronoi tessellations
Abstract

International audience; A full field crystal plasticity modelling of bimodal polycrystals is presented. Bimodal polycrystals are generated using a controlled Laguerre–Voronoi algorithm, and a modified phenomenological law is used to take into account the grain size effect through a Hall–Petch term. A focus is particularly made on the effects of grain size and of grain size ratio between ultrafine grains and coarse grains populations on local and global mechanical responses. The effect of the spatial distribution of the coarse grains (clustered or isolated) is also analysed in terms of strain localisation and stress concentration at the local scale.

Published
2020

26. Achieving good tensile properties in ultrafine grained nickel by spark plasma sintering

Author

Eric Hug, Clément Keller, Lucía García de la Cruz, Mayerling Martinez, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Nickel Ball milling, Spark plasma sintering, Sintering, Mechanical properties, 02 engineering and technology, 01 natural sciences, [SPI.MAT]Engineering Sciences [physics]/Materials, 0103 physical sciences, Ultimate tensile strength, [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], General Materials Science, Composite material, Ball mill, ComputingMilieux_MISCELLANEOUS, 010302 applied physics, Mechanical Engineering, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Microstructure, Grain size, Mechanics of Materials, Grain boundary, Ultrafine grained microstructure, 0210 nano-technology, Internal stresses, Electron backscatter diffraction
Abstract

International audience; In this work, the tensile properties of ultrafine grain Ni samples processed by spark plasma sintering are investigated. To this aim, a high purity Ni powder was nanostructured by ball milling using different processing conditions, and consolidation of the powder was performed by spark plasma sintering. Milling parameters were varied to produce samples with different microstructures. Each sample was characterised in terms of grain size and grain boundary character distribution to study the influence of milling parameters on the microstructure. Results show that suitable ball milling and subsequent sintering can be employed to obtain specimens with grain sizes in the ultrafine grain range with a high fraction of Σ3 grain boundaries. All samples exhibit a low internal stress state, which is evaluated in terms of grain orientation spread computed from electron backscatter diffraction and dislocation observation by transmission electron microscopy. Uniaxial tensile testing shows an increase in yield strength with grain refinement with a pronounced deviation from the Hall-Petch relation, for samples with grain sizes below 1.2 μm. Heterogeneity in deformation at yielding seems responsible for the deviation due to differences in the strain hardening behaviour between ultrafine grains and conventional coarse grains. All samples display high ductility with values of elongation to fracture above 35% as well as good toughness. The combination of ball milling with spark plasma sintering is therefore a promising tool to produce ultrafine grain Ni with good mechanical properties.

Published
2020

27. Experimental contribution for better understanding of ratcheting in 304L SS

Author

Clément Keller, Lakhdar Taleb, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Cyclic stress, Work (thermodynamics), Materials science, business.industry, Mechanical Engineering, Fatigue damage, 02 engineering and technology, Structural engineering, Mechanics, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Small strain, Stress (mechanics), 020303 mechanical engineering & transports, 0203 mechanical engineering, Creep, Mechanics of Materials, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], General Materials Science, Cyclic softening, 0210 nano-technology, business, ComputingMilieux_MISCELLANEOUS, Civil and Structural Engineering
Abstract

In this work our goal is to better understand the origin of the cyclic accumulation of the inelastic strain (often called ratcheting) observed in 304L SS subjected to uniaxial cyclic stress control at room temperature. Recent works performed in the frame of small strain assumption attribute this phenomenon essentially to creep (Taleb, 2013). However, outside this frame, it seems that creep is not the only contributor in this phenomenon (Facheris, 2014). New experiments are performed here in order to investigate the role played by creep, cyclic softening, fatigue damage, the mode of control (engineering or true stress) and ratcheting in this observation.

Published
2018

28. Influence of intermetallic compounds on the electrical resistivity of architectured copper clad aluminum composites elaborated by a restacking drawing method

Author

Alain Guillet, A. Gueydan, E. Guilmeau, Clément Keller, F. Moisy, Xavier Sauvage, Eric Hug, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), and Normandie Université (NU)

Subjects
Materials science, Annealing (metallurgy), Drawing, Intermetallic, chemistry.chemical_element, 02 engineering and technology, Bimetallic composite, 01 natural sciences, Electrical resistivity and conductivity, Aluminium, Intermetallic compound, 0103 physical sciences, lcsh:TA401-492, General Materials Science, Composite material, Porosity, ComputingMilieux_MISCELLANEOUS, 010302 applied physics, Architectured wire, Mechanical Engineering, Electrical resistivity, 021001 nanoscience & nanotechnology, Copper, chemistry, Mechanics of Materials, Volume fraction, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Aluminum composites, lcsh:Materials of engineering and construction. Mechanics of materials, 0210 nano-technology
Abstract

Architectured wires containing 61 restacked Copper Clad Aluminum (CCA) wires were cold-drawn down to a diameter of 1 mm without intermediate annealing. Samples were taken at intermediate diameters of 3 mm and 1.7 mm to observe the wire structure at different steps. Independently of the wire diameter, the structure did not exhibit any porosity and initial CCA wires were uniformly distributed inside the structure with constant equivalent diameters. Post-elaboration annealing treatments performed on CCA and architectured wires led to the formation of Al2Cu, AlCu and Al4Cu9 intermetallic compounds (IMC). It was shown that IMC growth kinetics do not depend on the wire diameter, indicating no marked influence of the plastic deformation. The volume fraction of IMC strongly increased with the reduction of the diameter and impacted the electrical resistivity of the architectured wire. The equivalent resistivity has been easily computed by a linear rule of mixture model, with three electrical resistances in parallel (Al, Cu and IMC), weighted by their respective volume fraction. This model allowed extracting a mean resistivity of IMCs of 4.5 μΩ·cm. It also demonstrated that this restacking drawing process, without any intermediate annealing treatment is an interesting method for the elaboration of architectured wires with optimized functional properties. Keywords: Bimetallic composite, Architectured wire, Drawing, Intermetallic compound, Electrical resistivity

Published
2018

29. Size effects and magnetoelastic couplings a link between Hall–Petch behaviour and coercive field in soft ferromagnetic metals

Author

Clément Keller, Eric Hug, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Université de Caen Normandie (UNICAEN), Centre National de la Recherche Scientifique (CNRS), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Magnetic domain, coercive field, 02 engineering and technology, 01 natural sciences, deformation mechanisms, 0103 physical sciences, [CHIM.CRIS]Chemical Sciences/Cristallography, [CHIM]Chemical Sciences, Texture (crystalline), Grain boundary strengthening, 010302 applied physics, internal stresses, Condensed matter physics, [CHIM.MATE]Chemical Sciences/Material chemistry, Coercivity, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Magnetocrystalline anisotropy, Grain size, size effects, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Deformation mechanism, Crystallite, magnetic properties, 0210 nano-technology
Abstract

International audience; Size effects regarding Hall–Petch (HP) relation are studied in this work for cobalt, nickel and Fe–3wt.%Si (FeSi), from polycrystalline to multicrystalline states. The materials show a breakdown in HP plot for thickness (t) to grain size (d) ratio less than a critical value. This appears in the beginning of plasticity for cobalt and FeSi whereas a plastic strain threshold must be overcome for nickel. Measurements of the coercive field on strained samples are able to depict such modification for low t/d ratio. Values of the coercive field in the polycrystalline domain allow an estimation of the magnetocrystalline anisotropy energy, related to the grain volume fraction concerned by reversal mechanisms for magnetic domains. Multicrystalline samples of cobalt and FeSi becomes magnetically softer at the yield stress. This is linked to a delay of the maximum intergranular stress towards higher strains for FeSi. For cobalt, non-linear elasticity and strong basal texture modify the magnetoelastic effects in coarse grain samples. For nickel, size effect on the coercive field appears after a few per cent of plastic strain as for HP relationship. A mean internal stress can be captured by magnetic measurements on polycrystals, related to the intragranular part of the kinematic stress. The softening of the magnetic properties for strained nickel multicrystals is due to a competition between the apparition of dislocation cells, which increases the coercive field by mechanisms of magnetic domain wall pinning, and surface softening of multicrystals, which tends to decrease the value of H c . © 2019, © 2019 Informa UK Limited, trading as Taylor and Francis Group.

Published
2019

30. Mechanical response of nickel multicrystals for shear and tensile conditions at room temperature and 573 K

Author

Anne Habraken, Olivier Milis, Laurent Duchene, Ehssen Betaieb, Clément Keller, Sibo Yuan, Cendrine Folton, and Eric Hug

Subjects
Shearing (physics), 0209 industrial biotechnology, Materials science, Stress path, Mechanical Engineering, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Grain size, Shear (sheet metal), Stress (mechanics), 020901 industrial engineering & automation, Mechanics of Materials, Ultimate tensile strength, General Materials Science, Crystallite, Composite material, 0210 nano-technology, Grain boundary strengthening
Abstract

The critical dimension (e.g. thickness for sheet, diameter for cylindrical part) of small components used in a miniaturized system is often a crucial factor affecting the mechanical behavior and the forming process, since in such length scale ranges the grain size is comparative to the mechanical part dimension. To have a better understanding of the mechanical behavior of microsized metallic parts, the size effects in 500 μm thick samples of nickel sheet were studied in tensile and shear loading states. The modifications of the mechanical behavior due to different numbers of grains across the thickness were thoroughly investigated at room temperature and 573 K. New experimental results obtained by shear tests at high temperature revealed that the transition from polycrystalline to multicrystalline behavior is more pronounced in tensile loading than in shearing conditions and that different surface sample state is observed. It was demonstrated that the reduced stress level effect depends not only on the temperature, but also on the stress state. In addition, with a moderate increase in temperature, the surface effects leading to the multicrystalline behaviors became more predominant in tensile condition than in shearing condition.

Published
2021

31. Microstructure and mechanical properties characterization of architectured copper aluminum composites manufactured by cold-drawing

Author

F. Moisy, N. Nguyen, Benoit Vieille, S. Eve, Clément Keller, Alireza Dashti, Alain Guillet, Xavier Sauvage, Eric Hug, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Normandie Université (NU)-Institut de Chimie du CNRS (INC)

Subjects
Materials science, Yield (engineering), Intermetallic, Mechanical properties, 02 engineering and technology, 01 natural sciences, Bimetal, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], Wire, 0103 physical sciences, Ultimate tensile strength, General Materials Science, Composite material, 010302 applied physics, Mechanical Engineering, Architectured microstructure, Recrystallization (metallurgy), Strain hardening exponent, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Microstructure, Metallic composite, Mechanics of Materials, Intermetallic compounds, Volume fraction, 0210 nano-technology
Abstract

International audience; The present study investigates the mechanical behavior of severely plastic-deformed Cu-Al composite wires with different diameters and heat-treatments. Each composite holds 61 restacked copper-clad aluminum wires. The bimetal composites were cold-worked up to diameters ranging from 1 mm to 3 mm, without any intermediate heat treatment. All the wires contain 61 hexagonal Cu-Al fibers with a continuous copper network extended from the outer surface into the center of the samples. Tensile tests were then performed on the as-drawn and heat treated wires. The latter were treated at 400 • C for 30 min and 6h. The heat treatments firstly induce recrystallization in both constituents, giving rise to a fine-grained microstructure and secondly prompt the formation of several intermetallics. Without heat treatment after processing, the architectured composites exhibit a ductility value similar to the conventional copper-clad aluminum wires and larger yield stresses compared to them, regardless of the diameter. The intermetallic compounds, forming as a result of heat treatment, affect the yield stress, ductility and strain hardening mechanisms. Finally, the results are discussed in terms of grain size, texture, intermetallics volume fraction and mechanical coupling between the phases.

Published
2021

32. Investigations on the fracture behavior of Inconel 718 superalloys obtained from cast and additive manufacturing processes

Author

Benoit Vieille, T. Breteau, F. Barbe, Clément Keller, Josiane Nguejio, H. Briatta, E. Baustert, M. Ben Azzouna, M. Mokhtari, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Normandie Université (NU)-Institut National des Sciences Appliquées (INSA), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de Biochimie des Protéines, Centre Hospitalier Régional Universitaire de Nancy (CHRU Nancy), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Volum-e, and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN)

Subjects
Materials science, Bending (metalworking), 02 engineering and technology, Edge (geometry), 01 natural sciences, [SPI.MAT]Engineering Sciences [physics]/Materials, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], Fracture toughness, [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], mental disorders, 0103 physical sciences, General Materials Science, Composite material, Inconel, ComputingMilieux_MISCELLANEOUS, 010302 applied physics, Mechanical Engineering, Fracture mechanics, [PHYS.MECA.MSMECA]Physics [physics]/Mechanics [physics]/Materials and structures in mechanics [physics.class-ph], 021001 nanoscience & nanotechnology, Condensed Matter Physics, Microstructure, Superalloy, Mechanics of Materials, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Fracture (geology), 0210 nano-technology
Abstract

This paper examines the effects of manufacturing processes on the fracture behavior of Inconel 718 alloy at room temperature. This comparative study was conducted on specimens obtained from cast and PBF (Power Bed Fusion) additive manufacturing. Mechanical testing was conducted on single edge notch specimens in bending. In order to quantify the influence of the manufacturing process on the fracture behavior, the J-R curves were obtained from the energy per unit of fracture surface area needed to drive crack growth in agreement with the ASTM standard E1820-01. Depending on the specimen type and the location of the initial notch with respect to the lasing planes, crack initiation significantly differs resulting from specific microstructures. These differences may explain why AM specimens have much higher fracture toughness at initiation (about 70–100%) and subsequent crack propagation. The in situ crack propagation was studied via the observations of the crack path along with the mechanical loading. An original picture analysis was developed to monitor the crack growth based on the location of the crack tip at specimen surface.

Published
2020

33. Tensile properties of spark plasma sintered AISI 316L stainless steel with unimodal and bimodal grain size distributions

Author

L. Garcia de la Cruz, Eric Hug, Baptiste Flipon, Fabrice Barbe, Clément Keller, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Tensile properties, Spark plasma sintering, 02 engineering and technology, engineering.material, 01 natural sciences, Sintering, Powder metallurgy, 0103 physical sciences, General Materials Science, Austenitic stainless steel, Composite material, Ductility, ComputingMilieux_MISCELLANEOUS, Stress concentration, 010302 applied physics, Bimodal microstructure, Mechanical Engineering, Metals and alloys, Strain hardening exponent, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Microstructure, Grain size, Mechanics of Materials, engineering, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology
Abstract

International audience; Powder metallurgy associated to spark plasma sintering was used to elaborate near full-dense samples of 316L austenitic stainless steel with unimodal or bimodal grain size distributions. To this aim, two different precursor powders were employed: a ball-milled one giving rise to ultrafine grains and a coarse one, as-received, for grains with conventional size. Sintered specimens were characterized in mechanical tension and their microstructure was revealed using transmission and scanning electron microscopy. Unimodal ultrafine grained samples show a large yield stress and a low ductility with a breakdown in the Hall-Petch relationship. For bimodal samples, a compromise between yield stress and ductility can be found. These features are then discussed in terms of strain mechanisms, grain size distribution and backstress. It is shown in particular that coarse grains contribute to enhance the ductility of the ultrafine grains matrix by modifying both the strain hardening mechanisms and the stress concentration areas.

Published
2018

34. A Novel Geometry for Shear Test Using Axial Tensile Setup

Author

Clément Keller, Olivier Milis, Laurent Duchene, Sibo Yuan, Anne Habraken, and Eric Hug

Subjects
in-plane shear, Materials science, finite element simulation, lcsh:A, Geometry, Finite element method, Clamping, Shear (geology), Ultimate tensile strength, thin specimen, Direct shear test, lcsh:General Works, Necking, Extensometer, Tensile testing
Abstract

This paper studies a novel geometry for the in-plane shear test performed with an axial electromechanical testing machine. In order to investigate the influence of the triaxiality rate on the mechanical behavior, different tests will be performed on the studied material: simple tensile tests, large tensile tests and shear tests. For the whole campaign, a common equipment should be employed to minimize the impact of the testing device. As a consequence, for the shear tests, the geometry of the specimen must be carefully designed in order to adapt the force value and make it comparable to the one obtained for the tensile tests. Like most of the existing shear-included tensile test specimens, the axial loading is converted to shear loading at a particular region through the effect of geometry. A symmetric shape is generally preferred, since it can restrict the in-plane rotation of the shear section, keep shear increasing in a more monotonic path and double the force level thanks to the two shear zones. Due to the specific experimental conditions, such as dimensions of the furnace and the clamping system, the position of the extensometer or the restriction of sheet thickness (related to the further studies of size effect at mesoscale and hot temperature), several geometries were brought up and evaluated in an iterative procedure via finite element simulations. Both the numerical and experimental results reveal that the final geometry ensures some advantages. For instance, a relatively low triaxiality in the shear zone, limited in-plane rotation and no necking are observed. Moreover, it also prevents any out-of-plane displacement of the specimen which seems to be highly sensitive to the geometry, and presents a very limited influence of the material and the thickness.

Published
2018

35. Kocks-Mecking analysis of the size effects on the mechanical behavior of nickel polycrystals

Author

Clément Keller, Eric Hug, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Normandie Université (NU)-Institut de Chimie du CNRS (INC)

Subjects
Materials science, Size effects, Mean free path, chemistry.chemical_element, 02 engineering and technology, 01 natural sciences, Stress level, Nickel, 0103 physical sciences, Ultimate tensile strength, Miniaturization, General Materials Science, Composite material, ComputingMilieux_MISCELLANEOUS, 010302 applied physics, Annihilation, Mechanical Engineering, Metallurgy, Strain hardening exponent, 021001 nanoscience & nanotechnology, Strengthening and mechanisms, Grain size, chemistry, Surface effects, Mechanics of Materials, Kocks-Mecking formalism, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology
Abstract

International audience; In this article, the Kocks-Mecking formalism is employed to analyze the grain size and thickness effects which modify the mechanical behavior of nickel polycrystals. To this aim, a two-internal variable Kocks-Mecking model, based on the evolution of forest and mobile dislocation densities, is numerically optimized using a wide experimental database of tensile curves of nickel polycrystals already published. The original model has been modified to take into account the grain size contribution to strain hardening in addition to the conventional dislocation production and annihilation terms. Using this improved model, the tensile curves of samples with different grain sizes, thicknesses and number of grains across the thickness are well reproduced. By means of an analysis of the model parameters, i.e. dislocation mean free path, cross-slip rate and dislocation densities, the strain mechanisms of nickel polycrystals are investigated as a function of their microstructural characteristics. For specimens with few grains across the thickness, the rate of dislocation annihilation is increased which, in turn, decreases the forest dislocation density and stress level. These results show, first, that the well-known Kocks-Mecking model is able to reproduce size effect and, second, confirm previous assumptions about the mechanical behavior of miniaturized samples. Eventually, the modeling of the mechanical behavior for samples concerned by miniaturization taking into account the surface effect contribution is discussed.

Published
2017

36. Elaboration of austenitic stainless steel samples with bimodal grain size distributions and investigation of their mechanical behavior

Author

Fabrice Barbe, Baptiste Flipon, Clément Keller, L. Garcia de la Cruz, Eric Hug, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010302 applied physics, Austenite, Materials science, Metallurgy, Spark plasma sintering, 02 engineering and technology, engineering.material, Plasticity, 021001 nanoscience & nanotechnology, 01 natural sciences, Grain size, Martensite, Powder metallurgy, 0103 physical sciences, Volume fraction, engineering, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Austenitic stainless steel, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS
Abstract

Samples of 316L austenitic stainless steel with bimodal grain size distributions are elaborated using two distinct routes. The first one is based on powder metallurgy using spark plasma sintering of two powders with different particle sizes. The second route applies the reverse-annealing method: it consists in inducing martensitic phase transformation by plastic strain and further annealing in order to obtain two austenitic grain populations with different sizes. Microstructural analy ses reveal that both methods are suitable to generate significative grain size contrast and to control this contrast according to the elaboration conditions. Mechanical properties under tension are then characterized for different grain size distributions. Crystal plasticity finite element modelling is further applied in a configuration of bimodal distribution to analyse the role played by coarse grains within a matrix of fine grains, considering not only their volume fraction but also their spatial arrangement.

Published
2017

37. Nanostructuration of metals via spark plasma sintering using activated powder obtained by ball-milling: Impact on the strain-hardening mechanisms

Author

Eric Hug, Mayerling Martinez, Clément Keller, Lucía García de la Cruz, Baptiste Flipon, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010302 applied physics, Materials science, Nanostructured materials, chemistry.chemical_element, Spark plasma sintering, 02 engineering and technology, Strain hardening exponent, engineering.material, 021001 nanoscience & nanotechnology, 01 natural sciences, Nickel, chemistry, Powder metallurgy, 0103 physical sciences, engineering, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Composite material, Austenitic stainless steel, 0210 nano-technology, Ball mill, ComputingMilieux_MISCELLANEOUS
Abstract

International audience; Powder metallurgy is a good option when coupled with pressure as a method to obtain nanostructured materials (NsM). The samples obtained by these means are nearly fully dense specimens that present low internal stresses. In this work, nickel is chosen to study the possibilities of nanostructuration via Spark Plasma Sintering (SPS) of ball-milled powders. The enhancement of the mechanical properties of the sintered samples are studied and compared with the results obtained for 316L austenitic stainless steel in a previous work.

Published
2017

38. Impact of Metallurgical Size Effects on Plasticity of Thin Metallic Materials

Author

Clément Keller, Eric Hug, and Anne Habraken

Subjects
Resistive touchscreen, Materials science, Computer simulation, Mechanical Engineering, Metallurgy, chemistry.chemical_element, Plasticity, Condensed Matter Physics, Copper, Grain size, chemistry, Mechanics of Materials, Aluminium, Formability, General Materials Science, Softening
Abstract

Three examples involving size effects are presented with implications concerning the formability: small Ni-20wt.%Cr resistive bridges, magnetic micro-sensors performed with (Ni, Co, Fe) based alloys and copper clad aluminum thin wires. The mechanical properties are directly linked to the ratio thickness over grain size (t/d ratio) of the parts. These metallurgical considerations must be taken into account when we are concerned by the numerical simulation of the process of such components. It is shown that the simulations can correctly reproduce the softening effect linked to a decrease in thickness and in number of grains across the thickness: the quality of the final shape strongly depends on the number of grains across the thickness. Finally the effect of a moderate increase in temperature on these results will be briefly reported.

Published
2014

39. Fatigue of Extruded 2017A Aluminum Alloy Subjected to Non-Proportional Loading Paths

Author

Mouaad Brik, Lakhdar Taleb, Clément Keller, Gael Marnier, Omar Allaoui, Université Amar Telidji - Laghouat, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Work (thermodynamics), Materials science, Mechanical Engineering, Metallurgy, Alloy, chemistry.chemical_element, engineering.material, Shear (sheet metal), Amplitude, chemistry, Mechanics of Materials, Aluminium, Fracture (geology), engineering, Cyclic loading, General Materials Science, Composite material, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Non proportional, ComputingMilieux_MISCELLANEOUS
Abstract

The present work is devoted to the study of the fatigue of an extruded aluminum alloy 2017A under cyclic loading in axial and shear directions at room temperature. Having the lifetime under a given axial amplitude σa (say, Nf_a) and the lifetime under a given torsional amplitude τa (say, Nf_t) [1], the objective here is to evaluate the lifetime when σa and τa are applied successively according to non-proportional path: σa then τa then σa then τa and so on until the fracture of the specimen. The obtained lifetime Nf_np is then compared to (Nf_a / 2 + Nf_t / 2). The obtained results point out the importance of the loading magnitude. Microstructural analyses have been performed to better understand the fracture mechanisms for the different cases of loadings.

Published
2016

40. Towards a Better Understanding of the Ratcheting Phenomenon

Author

Lakhdar Taleb, Clément Keller, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), and Normandie Université (NU)

Subjects
010302 applied physics, Cyclic stress, Work (thermodynamics), Materials science, business.industry, Mechanical Engineering, Fatigue damage, 02 engineering and technology, Mechanics, Structural engineering, 021001 nanoscience & nanotechnology, 01 natural sciences, Small strain, Creep, Mechanics of Materials, Phenomenon, 0103 physical sciences, General Materials Science, Cyclic softening, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, business, ComputingMilieux_MISCELLANEOUS
Abstract

In this work our goal is to better understand the origin of the cyclic accumulation of the inelastic strain (often called ratcheting) observed in 304L SS subjected to uniaxial cyclic stress control at room temperature. Recent works performed in the frame of small strain assumption attribute this phenomenon essentially to creep [1]. However, outside this frame, it seems that creep is not the only contributor in this phenomenon [2]. New experiments are performed here in order to investigate the role played by creep, cyclic softening, fatigue damage and ratcheting in this observation.

Published
2016

41. Temperature dependence and size effects on strain hardening mechanisms in copper polycrystals

Author

Eric Hug, Clément Keller, Pierre-Antoine Dubos, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Université de Caen Normandie (UNICAEN), Normandie Université (NU), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, chemistry.chemical_element, 02 engineering and technology, Work hardening, Cubic crystal system, 01 natural sciences, [SPI.MAT]Engineering Sciences [physics]/Materials, Metal, [SPI]Engineering Sciences [physics], 0103 physical sciences, General Materials Science, Composite material, ComputingMilieux_MISCELLANEOUS, 010302 applied physics, Mechanical Engineering, Metallurgy, Strain hardening exponent, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Copper, Nickel, chemistry, Mechanics of Materials, visual_art, Hardening (metallurgy), visual_art.visual_art_medium, Crystallite, 0210 nano-technology
Abstract

The thermomechanical behavior of polycrystalline sheets of high purity copper with various numbers of grains (d) across the thickness (t) is experimentally analyzed. As for other face centered cubic materials, the t/d ratio strongly affects the work hardening of copper, especially for t/d values lower than a critical one around five. These results are in agreement with previous ones concerning nickel and can be correlated with surface effects which progressively take place in the material when few grains are present across the thickness. The t/d ratio mainly affects the second work hardening stage and an increase in temperature tends to reduce this effect due to the early beginning of cross slip which leads to a generalization of the surface properties on the overall volume of the material. This result is supported by the analysis of the dislocation structures during the second and third hardening stages for polycrystalline and multicrystalline specimens. As a consequence, the forming of thin metallic products should be ideally performed at moderate temperatures in order to avoid size effects which can deteriorate the reliability of the final product.

Published
2013

42. Influence of Spark Plasma Sintering Conditions on the Sintering and Functional Properties of an Ultra-Fine Grained 316L Stainless Steel Obtained from Ball-Milled Powder

Author

Gaël Marnier, Jacques G. Noudem, K. Tabalaiev, Clément Keller, Eric Hug, Xavier Sauvage, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Normandie Université (NU)-Institut de Chimie du CNRS (INC)

Subjects
Materials science, Sintering, Spark plasma sintering, 02 engineering and technology, engineering.material, 01 natural sciences, Stainless steel, Powder metallurgy, 0103 physical sciences, General Materials Science, Austenitic stainless steel, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Plasma sintering, ComputingMilieux_MISCELLANEOUS, 010302 applied physics, Functional properties, Mechanical Engineering, Metallurgy, Ultra-fine grain, Intergranular corrosion, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Microstructure, Grain size, Mechanics of Materials, engineering, Crystallite, 0210 nano-technology
Abstract

International audience; In this work, 316L samples with submicrometric grain size were sintered by spark plasma sintering. To this aim, 316L powder was first ball-milled with different conditions to obtain nanostructured powder. The process control agent quantity and milling time were varied to check their influence on the crystallite size of milled powder. Samples were then sintered by spark plasma sintering using different sets of sintering parameters (temperature, dwell time and pressure). For each sample, grain size and density were systematically measured in order to investigate the influence of the sintering process on these two key microstructure parameters. Results show that suitable ball-milling and subsequent sintering can be employed to obtain austenitic stainless steel samples with grain sizes in the nanometer range with porosity lower than 3%. However, ball-milling and subsequent sintering enhance chromium carbides formation at the sample surface in addition to intragranular and intergranular oxides in the sample as revealed by X-ray diffraction and transmission electron microscopy. It has been shown that using Boron nitride together with graphite foils to protect the mold from powder welding prevent such carbide formation. For mechanical properties, results show that the grain size refinement strongly increases the hardness of the samples without deviation from Hall-Petch relationship despite the oxides formation. For corrosion resistance, grain sizes lower than a few micrometers involve a strong decrease in the pitting potential and a strong increase in passivation current. As a consequence, spark plasma sintering can be considered as a promising tool for ultra-fine grained austenitic stainless steel.

Published
2016

43. Multiscale Analysis of the Pre-Hardening Effect on the Cyclic Behavior and Fatigue Life of 304L Stainless Steel

Author

Lakhdar Taleb, Clément Keller, Adel Belattar, Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), ERMECA (ERMECA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université de Rouen Normandie (UNIROUEN), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), and Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie)

Subjects
Materials science, Mechanical Engineering, Effective stress, Metallurgy, High density, macromolecular substances, 02 engineering and technology, Flow stress, engineering.material, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Fatigue limit, 020303 mechanical engineering & transports, Amplitude, 0203 mechanical engineering, Shear (geology), Mechanics of Materials, engineering, General Materials Science, Austenitic stainless steel, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, Hardening effect, ComputingMilieux_MISCELLANEOUS
Abstract

This study investigates the effects of axial and shear cyclic pre-hardening on cyclic behavior and fatigue life of an austenitic stainless steel 304L at room temperature. First of all, the effect of cyclic sequential loading with increasing and decreasing strain amplitude on the cyclic stress-strain curve has been confirmed. Then, the fatigue life of the specimens previously subjected to four increasing-decreasing sequences of pre-straining was investigated. The application of the sequential loading as a pre-hardening made the investigation of the pre-hardening effect without any influence of the mean stress and mean strain possible. Compared to virgin specimens, pre-hardened samples have shown larger flow stress and significantly reduced lifetimes. However, an increase in the strain amplitude during the fatigue test reduced the effect of the pre-hardening. The dislocations observing has shown that pre-strained samples inherit high density of dislocations, structured from the pre-hardening sequence, thus increasing both flow stress and damage. These results were then discussed in terms of long-range backstress and effective stress evolution.

Published
2016

44. Tensile Prestrain Memory Effect on Subsequent Cyclic Behavior of FCC Metallic Materials Presenting Different Dislocations Slip Modes

Author

Clément Keller, Gaël Marnier, Lakhdar Taleb, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Alloy, 02 engineering and technology, Slip (materials science), Cubic crystal system, engineering.material, Plasticity, Metal, 0203 mechanical engineering, Ultimate tensile strength, General Materials Science, Composite material, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], ComputingMilieux_MISCELLANEOUS, business.industry, Mechanical Engineering, Forming processes, Structural engineering, 021001 nanoscience & nanotechnology, 020303 mechanical engineering & transports, Mechanics of Materials, visual_art, visual_art.visual_art_medium, engineering, 0210 nano-technology, business, Stacking fault
Abstract

The forming process of metallic products generally implies steps of large plastic deformation. Understanding the “memory” of this prestrain history on subsequent fatigue properties is therefore an important industrial requirement as well as a challenging objective. Following this purpose, the cyclic behavior of Face Centered Cubic (FCC) metals was investigated after different tensile prestrains and compared with the cyclic stress-strain responses of the virgin samples. In the past, dislocations slip character was clearly highlighted as a significant factor influencing prestrain memory and the different materials sensibilities to this phenomenon were discussed on the basis of their stacking fault energies. Nonetheless, the domain of memory occurrence and its evolution as a function of cross slip ease remain unclearly defined. This paper will provide some clues in this matter by drawing cartographies of memory effect in the case of pure copper (easy cross slip), nickel-chromium alloy (planar slip) and 316L stainless steel (mixed behavior) subjected to axial loading at room temperature. From these cartographies, the existence of threshold of prestrain necessary to induce memory and threshold of plastic strain amplitude capable to erase memory will be discussed.

Published
2016

45. Size effects and temperature dependence on strain-hardening mechanisms in some face centered cubic materials

Author

Pierre-Antoine Dubos, Clément Keller, Anne Habraken, Eric Hug, Laurent Duchene, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Departement Architecture, Géologie, Environnement et Constructions - ArGEnCo (Liège, Belgium), Université de Liège, Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Size effects, Thermomechanical behavior, Condensed matter physics, Plasticity, Strain gradient plasticity model, Slip (materials science), Work hardening, Strain hardening exponent, Cubic crystal system, Grain size, Face centered cubic materials, Deformation mechanism, Mechanics of Materials, Dislocation substructures, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], General Materials Science, Crystallite, Instrumentation
Abstract

The mechanical behavior of face centered cubic metals is deeply affected when specimen dimensions decrease from a few millimeters to a few micrometers. At room temperature, a critical thickness ( t ) to grain size ( d ) ratio ( t / d ) c was previously highlighted, under which the softening of mechanical properties became very pronounced both in terms of Hall–Petch relation and work hardening mechanisms. In this work, new experimental results are provided concerning the influence of temperature on this size effect for copper, nickel and Ni–20 wt.%Cr, representative of a wide range of deformation mechanisms ( i.e. dislocation slip character). It is shown that multicrystalline samples ( t / d t / d ) c ) are not deeply affected by an increase in temperature, independently of the planar or wavy character of dislocation glide. For pronounced wavy slip character metals, surface effects in polycrystals ( t / d > ( t / d ) c ) are not significant enough to reduce the gap between polycrystal and multicrystal mechanical behavior when the temperature increases. However, a transition from wavy slip to planar glide mechanisms induces a modification of the polycrystalline behavior which tends toward multicrystalline one with a moderate increase in temperature. This work demonstrates that surface effects and grain size influence can be successfully disassociated for the three studied materials using an analysis supported by the Kocks–Mecking formalism. All these results are supported by microscopic investigations of dislocation substructures and compared to numerical simulations using a strain gradient plasticity model.

Published
2015

46. Influence of the temperature on the tensile behaviour of a modified 9Cr–1Mo T91 martensitic steel

Author

Ivan Guillot, Zehoua Hadjem-Hamouche, Monique Margulies, Clément Keller, Institut de Chimie et des Matériaux Paris-Est (ICMPE), and Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
010302 applied physics, Materials science, Mechanical Engineering, Metallurgy, 02 engineering and technology, Plasticity, Flow stress, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, [SPI.MAT]Engineering Sciences [physics]/Materials, Deformation mechanism, Mechanics of Materials, Martensite, [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], 0103 physical sciences, Ultimate tensile strength, General Materials Science, Dislocation, 0210 nano-technology, Ductility, ComputingMilieux_MISCELLANEOUS, Tensile testing
Abstract

The tensile behaviour of a modified 9Cr–1Mo T91 martensitic steel is investigated for temperatures between 300 and 700 K. Loading/unloading tensile tests are carried out to investigate the evolution of the tensile flow parameters and the different flow stress components with temperature. An increase in temperature reduces the ductility and the ultimate tensile stress. Three different deformation mechanisms are operative depending on the temperature. These mechanisms are discussed in terms of activation volume, dislocation motion and dynamic strain ageing.

Published
2010

47. Influence of the stacking fault energy and temperature on the prestrain memory effect of face centered cubic metal submitted to cyclic loadings

Author

Clément Keller, Gaël Marnier, Wilson Veloz, Lakhdar Taleb, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Cyclic stress, Effective stress, Alloy, 02 engineering and technology, Slip (materials science), Flow stress, engineering.material, Cubic crystal system, 021001 nanoscience & nanotechnology, 020303 mechanical engineering & transports, 0203 mechanical engineering, Deformation mechanism, lcsh:TA1-2040, Stacking-fault energy, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], engineering, Composite material, lcsh:Engineering (General). Civil engineering (General), 0210 nano-technology, ComputingMilieux_MISCELLANEOUS
Abstract

In this paper, the effect of a monotonic prehardening in tension on the subsequent cyclic stress strain curves is investigated as a function of the deformation mechanisms. To this aim, three materials are employed, copper for wavy dislocation slip, Ni20Cr alloy for planar slip and AISI 316L for intermediate deformation mechanisms. Samples were first prestrained in tension and then submitted to incremental strain cyclic tests at room temperature, and also 200°C for the 316L. Based on the analysis of the flow stress components (backstress and effective stress), the results show that all materials are sensitive to a prehardening depending on the prestrain level and cyclic test characteristics (amplitude and temperature).

Published
2018

48. TEM study of dislocation patterns in near-surface and core regions of deformed nickel polycrystals with few grains across the cross section

Author

X. Feaugas, Richard Retoux, Clément Keller, Eric Hug, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Laboratoire d'Etude des Matériaux en Milieux Agressifs (LEMMA), Université de La Rochelle (ULR), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), and La Rochelle Université (ULR)

Subjects
010302 applied physics, Materials science, chemistry.chemical_element, 02 engineering and technology, Flow stress, 021001 nanoscience & nanotechnology, 01 natural sciences, [SPI.MAT]Engineering Sciences [physics]/Materials, Stress (mechanics), Core (optical fiber), Nickel, chemistry, Mechanics of Materials, Free surface, [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], 0103 physical sciences, General Materials Science, Grain boundary, Crystallite, Composite material, Dislocation, 0210 nano-technology, Instrumentation, ComputingMilieux_MISCELLANEOUS
Abstract

TEM investigations of dislocation structures in core and surface regions (50 μm below the free surface) were carried out on polycrystalline nickel samples of 500 μm thickness with 14, 2.5 and 1 grain across the thickness. The mean diameter of the dislocation cells was measured for different strain levels in core and surface regions of the three kinds of sample. These mean dislocation cell diameters were compared between the different samples using a statistical analysis of variance. The intragranular long-range internal backstress level was thereafter estimated in both regions for the three samples revealing a decrease in stress for specimens with few grains across the thickness. This decrease is partially responsible for the flow stress decrease of the nickel polycrystals with few grains across the thickness.

Published
2010

49. Size effects and Hall–Petch relation in polycrystalline cobalt

Author

Clément Keller, Mayerling Martinez, Pierre-Antoine Dubos, Eric Hug, Gwendoline Fleurier, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU), Groupe de physique des matériaux (GPM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN)

Subjects
010302 applied physics, Materials science, Condensed matter physics, 02 engineering and technology, Slip (materials science), Work hardening, Flow stress, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Grain size, Crystallography, Deformation mechanism, Deformation twinning, 0103 physical sciences, Deformation mechanisms, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Crystallite, Polycrystalline cobalt, Size effect, 0210 nano-technology, Crystal twinning, Grain boundary strengthening
Abstract

International audience; The mechanical behaviour of polycrystalline hexagonal close-packed cobalt was investigated over a large range of grain size d in order to examine the occurrence of size effects. Crystallographic texture and amount of face centred cubic allotropic phase were maintained unchanged thanks to appropriate heat treatment procedures. The Hall–Petch (HP) relation exhibits two distinct behaviours from the very beginning of plastic strain levels. The conventional HP law is fulfilled for a number of grains across the thickness t higher than a critical value (t/d)c = 14. For t/d lower than (t/d)c, a multicrystalline regime is evidenced highlighting a strong reduction in flow stress. The high value of (t/d)c is related to the low-stacking fault energy of cobalt in the basal plane. The size effect is predominant in the first work hardening stage where slip mechanisms and stacking faults predominate. In the second stage, driven by mechanical twinning processes, this effect is less sensitive. Finally, the size effect could also affect the end of the elastic stage, in link with nonlinear elasticity mechanisms.

Published
2015

50. Functional properties of a spark plasma sintered ultrafine-grained 316L steel

Author

Jacques G. Noudem, Gaël Marnier, Eric Hug, Clément Keller, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], Materials science, [SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment, Metallurgy, Spark plasma sintering, Corrosion resistance, Forming processes, Plasma, engineering.material, Microstructure, Chloride, Characterization (materials science), Corrosion, [SPI.MAT]Engineering Sciences [physics]/Materials, [SPI]Engineering Sciences [physics], Hardness, Ultrafine grained stainless steel, [SDE]Environmental Sciences, engineering, medicine, Austenitic stainless steel, medicine.drug
Abstract

International audience; A micrometric austenitic stainless steel 316L powder was densified by spark plasma sintering. The process parameters were varied over wide ranges and the impact of such variations on sintered materials was studied through the characterization of their microstructures, densities, hardness and corrosion resistance. For comparison with the properties of traditionally cast 316L, all these investigations were also systematically carried out on as cast samples. The sintered stainless steel produced this way was highly densified, with grains of a micrometric size and the forming process did not induce any residual strain gradients as shown by transmission electronic microscopy analysis. The investigation of the corresponding mechanical properties reveals an enhancement of hardness up to twice the value measured on one sample of as cast 316L. This result is in good agreement with the Hall–Petch formalism. Additionally, in the matter of corrosion behavior, fully dense samples display an enhanced passive state in chloride media compared to as cast material. Spark plasma sintering appears to be an interesting alternative elaboration way of ultrafine 316L stainless steel giving materials with high stress resistance, without strain gradients through the volume, and promising functional properties concerning corrosion behavior.

Published
2014

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