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Regarding severely deformed materials of potentially high applicability in various industry branches, their microstructure evolution during processing is of vast significance as it enables to control or adjust the most essential properties, including mechanical strength or corrosion resistance. Within the present study, the microstructure development of commercially pure titanium (grade 2) in the multi-stage process of hydrostatic extrusion has been studied with the use of the well-established techniques, involving electron backscatter diffraction as well as transmission electron microscopy. Microstructural deformation-induced defects, including grain boundaries, dislocations, and twins, have been meticulously analyzed. In addition, a special emphasis has been placed on grain size, grain boundary character as well as misorientation gradients inside deformed grains. The main aim was to highlight the microstructural alterations triggered by hydroextrusion and single out their possible sources. The crystallographic texture was also studied. It has been concluded that hydrostatically extruded titanium is an exceptionally inhomogeneous material in terms of its microstructure as evidenced by discrepancies in grain size and shape, a great deal of dislocation-type features observed at every single stage of processing and the magnitude of deformation energy stored. Twinning, accompanied by grain subdivision phenomenon, was governing the microstructural development at low strains; whereas, the process of continuous dynamic recrystallization came to the fore at higher strains.Selected mechanical properties resulting from the studied material microstructure are also presented and discussed.

The phenomenon of superior biological behavior , r it observed in titanium processed by an unconventional severe plastic deformation method, that is, hydrostatic extrusion, has been described within the present study. In doing so, specimens varying significantly in the crystallographic orientation of grains, yet exhibiting comparable grain refinement, were meticulously investigated. The aim was to find the clear origin of enhanced biocompatibility of titanium-based materials, having microstructures scaled down to the submicron range. Texture, microstructure, and surface characteristics, that is, wettability, roughness, and chemical composition, were examined as well as protein adsorption tests and cell response studies were carried out. It has been concluded that, irrespective of surface properties and mean grain size, the (10 (1) over bar0) crystallographic plane favors endothelial cell attachment on the surface of the severely deformed titanium. Interestingly, an enhanced albumin, fibronectin, and serum adsorption as well as dearly directional growth of the cells with preferentially oriented cell nuclei have been observed on the surfaces having (0001) planes exposed predominantly. Overall, the biological response of titanium fabricated by severe plastic deformation techniques is derived from the synergistic effect of surface irregularities, being the effect of refined microstructures, surface chemistry, and crystallographic orientation of grains rather than grain refinement itself.

Abstract Modification of microstructure parameters of severely deformed 1050 aluminum after 5 years of recovery at ambient temperature was studied. The samples of 1050 aluminum were extruded using ECAP technique. The EBSD maps were recorded for the initial material and for the deformed samples. Next, the latter samples were left at ambient temperature during 5 years and a full EBSD study of the material was repeated. It was found that all microstructure parameters and textures have changed after this period. This is due to recovery and partial recrystallization, which took place in the samples during 5 years. The presented modifications of material microstructure are important, e.g., in the aspect of long time service of mechanical parts produced by severe plastic deformation techniques. Graphic Abstract

In this work, the evolutions of stresses in both phases of the Al/SiCp composite subjected to thermal cycling during in situ compression test were measured using Time of Flight neutron diffraction. It was confirmed that inter-phase stresses in the studied composite can be caused by differences in the coefficient of thermal expansion for the reinforcement and matrix, leading to a different variation of phase volumes during sample heating or cooling. The results of the diffraction experiment during thermal cycling were well predicted by the Thermo-Mechanical Self-Consistent model. The experimental study of elastic-plastic deformation was carried out in situ on a unique diffractometer EPSILON-MDS (JINR in Dubna, Russia) with nine detector banks measuring interplanar spacings simultaneously in 9 orientations of scattering vector. For the first time, the performed analysis of experimental data allowed to study the evolution of full stress tensor in both phases of the composite and to consider the decomposition of this tensor into deviatoric and hydrostatic components. It was found that the novel Developed Thermo-Mechanical Self-Consistent model correctly predicted stress evolution during compressive loading, taking into account the relaxation of thermal origin hydrostatic stresses. The comparison of this model with experimental data at the macroscopic level and the level of phases showed that strengthening of the Al/SiCp composite is caused by stress transfer from the plastically deformed Al2124 matrix to the elastic SiCp reinforcement, while thermal stresses relaxation does not significantly affect the overall composite properties.

Selective laser melted Titanium grade 23 was characterized by low porosity, relatively large surface roughness and pronounced surface texture (i.e. surface grooves orientation). The band/layer microstructure was built of mixed α and β phases. The as printed structure exhibited very high compressive residual stresses with strong anisotropy (i.e., − 512 ± 17 MPa and − 282 ± 14 MPa along the laser scanning direction and along the transverse direction, respectively) and strong fiber crystallographic texture. The latter one is responsible for the anisotropy of hardness in the material. Annealing at 600 °C during four hours significantly removed residual stresses (i.e. to − 14 ± 2.8 MPa) and slightly weakened the texture. Yield strength, 1120 ± 50 MPa, and ultimate tensile strength, 1210 ± 50 MPa, of the annealed material are significantly higher and tensile elongation, 3.9%, lower than for commercial Titanium grade 23. Final mechanical polishing to obtain flat and relatively smooth surface induced desired compression residual stress in the subsurface (i.e., equal to about − 90 MPa). Low absorbed gas contents (oxygen, nitrogen, hydrogen) and low porosity of the printed material indicates the correctness of the technology and allows the printed material to be classified as meeting the requirements of ASTM standards for Titanium grade 23. Besides traditional testing techniques, the optical profilometry, X-ray analysis (texture and residual stresses measurement) and infrared absorption method were applied for the product characterization and some potential of these testing methods and usefulness in technological practice was discussed, what can be particularly interesting both to practitioners from industry and researches from scientific laboratories.

Characterisation of the residual stresses at a scale of polycrystalline grains is the main topic of this work. The grazing incidence X-ray diffraction during “in situ” tensile test and a novel method of experimental data interpretation allowed to determine the evolution of macroscopic and intergranular stresses (the second order stresses) during elastic-plastic deformation and elastic unloading of AZ31 alloy sample. Additionally, the values of the critical resolved shear stresses were determined for slip systems activated during plastic deformation. A new important finding of this work is the determination of significant residual intergranular stresses in textured magnesium alloy subjected to plastic deformation. These stresses are correlated with the orientation of basal plane with respect to the applied stress, and they can be explained by a large difference between critical resolved shear stress values for basal and non-basal slip systems. In contrast to the magnesium alloy studied in this work, low values of the second order stresses were found previously in a two-phase Ti alloy due to the small difference between critical resolved stresses in both phases.

The present work deals with the investigation of the micromechanical behaviour of a duplex steel, which consists of two phases (austenite and ferrite) exhibiting significantly different mechanical properties. The stresses in both phases were experimentally determined in the elastic and plastic ranges of deformation using synchrotron radiation diffraction experiments. The used methodology enabled to determine the values of initial stresses and to study the evolutions of the principal phase stresses and the second order stresses during the elastic, as well as the plastic range of deformation. With the help of a self-consistent model, the critical resolved shear stresses and the work hardening parameters for slip systems, active in each phase, were also estimated. Comparison of the measured phase stresses and lattice strains evolutions with the model results showed a good agreement between prediction and experiment when the initial stress state in the sample and shape of grains approximated by ellipsoidal inclusions were taken into account. The overall outcome of the work is the determination of stress partitioning between the two phases of a polycrystalline material for all deformation stages, determined directly from diffraction experiment. The results enabled analyses of von Mises, hydrostatic stresses as well as second order stresses evolutions in both phases during tensile deformation. Finally, the experimental data were successfully compared with predictions of the self-consistent deformation model.

The main purpose of this work is to develop neutron diffraction methodology in order to determine stresses localised in polycrystalline grains during elastoplastic deformation, directly from experiment. As a result, for the first time, the von Mises stress for chosen grain orientations and Critical Resolved Shear Stresses (CRSS) for active slip systems were unambiguously measured without the help of crystallographic models, which introduce different theoretical assumptions. The stresses measured for groups of grains and the determined CRSS values are important characteristics of a material, which allow to study plastic deformation in textured material at different scales: slip system and grain, which play a key role in mechanical properties and formability of the material. The new method was successfully tested and applied to textured AZ31 alloy subjected to tensile deformation and the components of stress tensor were for the first time determined from measured lattice strains corresponding to chosen orientations of crystallite lattice. The obtained results positively verified hypotheses that, during plastic deformation, a large difference in the hardness as well as in the localised stresses occurs for grains having different lattice orientations. It was found directly from experiment that, the activation of basal glide, having small CRSS, does not lead to significant plastic deformation, and the activation of other non-basal systems (with higher CRSS) induces the development of plasticity at the macroscopic scale. The early plastic deformation occurring due to slip on basal system is small but it can destructively affect fatigue life, limiting applicability of the material for structural components. Finally, the comparison of experimental results with a modified version of Elastic-Plastic Self-Consistent (EPSC) model showed its capability to simulate the mechanical behaviour of such materials.

The stress partitioning between phases, phase stress relaxation as well as origins of Al/SiCp composite strengthening are studied in the present work. In this aim, the measurements of lattice strains by neutron diffraction were performed in situ during tensile test up to sample fracture. The experimental results were compared with results of elastic–plastic self-consistent model. It was found that thermal origin phase stresses relax at the beginning of plastic deformation of Al/SiCp composite. The evolution of lattice strains in both phases can be correctly simulated by the elastic–plastic self-consistent model only if the relaxation of initial stresses is taken into account. A major role in the strengthening of the studied composite plays a transfer of stresses to the SiCp reinforcement, however the hardness of Al metal matrix is also important.

In this work samples of commercial purity grade 2 titanium were severely deformed by three different extrusion techniques: equal-channel angular pressing (ECAP), extrusion through oscillating die (KOBO), and hydrostatic extrusion (HE). Resulting microstructures and mechanical properties of processed titanium samples are studied and compared with regard to potential application as a material for dental implants. The obtained results demonstrate the effect of different strain paths, involved by three applied deformation methods, on microstructure refinement, mechanical properties and textures of the studied material. Heterogeneous microstructures with bimodal grain size distributions are observed for all deformation techniques in the examined material, however differences in their internal structures and grain boundary distributions point to different grain refinement mechanisms. The fraction of ultra-fine grains is the highest in titanium deformed by HE. Also the internal grain fragmentation is the most important after HE deformation. This leads to the best mechanical and microstructural properties obtained in this type of deformation. Consequently, the HE process seems to be very interesting for production of material for medical implants.

The deformation behavior of commercially pure titanium is studied using experiments and a crystal plasticity model. Compression tests along the rolling, transverse, and normal-directions, and tensile tests along the rolling and transverse directions are performed at room temperature to study the activation of slip and twinning in the hexagonal closed packed titanium. A detailed EBSD based statistical analysis of the microstructure is performed to develop statistics of both {10−12} tensile and {11−22} compression twins. A simple Monte Carlo (MC) twin variant selection criterion is proposed within the framework of the visco-plastic self-consistent (VPSC) model with a dislocation density (DD) based law used to describe dislocation hardening. In the model, plasticity is accommodated by prismatic, basal and pyramidal slip modes, and {10−12} tensile and {11−22} compression twinning modes. The VPSC-MC model successfully captures the experimentally observed activation of low Schmid factor twin variants for both tensile and compression twins modes. The model also predicts macroscopic stress-strain response, texture evolution and twin volume fraction that are in agreement with experimental observations.

A detailed statistical analysis is performed using Electron Back Scatter Diffraction (EBSD) to establish the effect of microstructure on twin nucleation and growth in deformed commercial purity hexagonal close packed (HCP) titanium. Rolled titanium samples are compressed along rolling, transverse and normal directions to establish statistical correlations for {10–12}, {11–21}, and {11–22} twins. A recently developed automated EBSD-twinning analysis software is employed for the statistical analysis. The analysis provides the following key findings: (I) grain size and strain dependence is different for twin nucleation and growth; (II) twinning statistics can be generalized for the HCP metals magnesium, zirconium and titanium; and (III) complex microstructure, where grain shape and size distribution is heterogeneous, requires multi-point statistical correlations.

In the present work the properties of titanium grade 2 after ECAP processing with original route and regimes (route C, channel angle $$\varPhi$$ = 120°, deformation temperature 300 °C, number of passes up to 8) were examined. Texture development and microstructure parameters after ECAP processing and after recrystallization were determined using electron back scatter diffraction and analysed. A significant increase of the mechanical strength accompanied by some increase of ductility was observed in the deformed samples. The kernel average misorientation and average grain orientation spread were strongly increased after deformation, which confirms the material refinement and fragmentation. The proportion of low angle boundaries increased after four ECAP passes, but after four consecutive passes high angle grain boundaries became predominant. No deformation twins were observed after four and eight ECAP passes. The material recrystallized after deformation retained a fine grain microstructure. The textures of deformed and recrystallized samples were determined. It was found that texture after 8 passes is more homogeneous that that after 4 passes, which partly explains higher ductility of this first sample.

The goal of this work was theoretical and experimental study of micro- and macroscopic mechanical fields of 6061 aluminum alloy induced by the asymmetric rolling process. Two-scale constitutive law was used by implementing an elasto-plastic self-consistent scheme into the Finite Element code (ABAQUS/Explicit). The model was applied to study the asymmetric rolling. Such a deformation process induces heterogeneous mechanical fields that were reproduced by the model thanks to the crystallographic nature of constitutive law used. The studied material was processed, at room temperature, in one rolling pass to 36% reduction. The resulting material modifications were compared with predictions of the two-scale model. Namely, the calculated textures were compared with experimental ones determined by X-ray diffraction. Especially, detailed quantitative analysis of texture variation across the sample thickness was done. The influence of this texture variation on plastic anisotropy was studied. The advantages of asymmetric rolling process over symmetric one were identified. The main benefits are a nearly homogeneous crystallographic texture, reduced rolling normal forces and homogenization of plastic anisotropy through the sample thickness.

Texture modifications of polycrystalline copper, caused by asymmetric rolling, were studied experimentally and theoretically analysed. Orientation distribution functions and its intensity along the skeleton lines were examined. It was found that texture components after asymmetric rolling are rotated, approximately around transverse direction, as compared with those after symmetric rolling. The rotation angles were determined for characteristic texture components as a function of the rolling asymmetry ratio. Texture heterogeneity across the rolled sheet thickness was also studied. Theoretical predictions of rolling textures were done using two crystalline deformation models. The orientation distribution functions, rotations of texture components and their variation across the sample thickness were determined and compared with theoretical results. Also the stability of final orientations after asymmetric rolling texture was tested.

The goal work of this work is to describe the qualitative and quantitative behaviour of titanium T40 during tensile test. Material characteristics were determined using EBSD and X-ray techniques. Textures, twin boundary fractions, residual stresses and coherent domain size were determined. It was found that deformation mechanisms and microstructure characteristics are different in the samples stretched along rolling and transverse directions. For example the average grain size, as determined from EBSD measurements, is higher in the sample stretched along rolling direction. Also smaller coherent domains form and residual stress is more easily relaxed in this sample. A strong appearance of tensile twins was observed in the samples deformed along transverse direction. In the present paper a complex study of material characteristics and deformation mechanisms is presented. A special emphasis is done on residual stress characteristics determined in the samples stretched in two perpendicular directions.

The problem of ambiguity in the definition of lattice rotation, used in plastic deformation models, is examined in this work. The geometry of tensile and compression deformation is considered. Two approaches to lattice rotation are considered: the classical definition (called also ‘mathematical analysis’) and the definition based on orientation preservation of specified directions/planes in the sample coordinates system. Similar study was already done by the present authors for the geometry of rolling deformation. It was shown that application of two rotation definitions enables to explain the appearance of two types of f.c.c. rolling textures: brass type and copper type textures. In the case of axisymmetric deformation the application of both definitions of lattice rotation leads to similar textures, but with different spread of their principal components.

The process of asymmetric rolling, as an alternative to the symmetric rolling, attracts attention of many researchers and technologists. Asymmetric rolling can modify rolling process parameters like normal forces and torques, sample shape (by bending) or power requirements. It can also change material properties. The enhanced shear deformation, characteristic for this process, leads to microstructure refinement, increase of material strength and texture rotation. Asymmetric rolling can be realized by a modification of existing rolling mills, therefore its industrial application is possible at a relatively low cost. In this aspect, the case of a moderate rolling asymmetry and moderate deformation in one rolling pass was examined; these parameters can be attained on typical industrial rolling mills. The aim of the present study is to characterize this process and resulting material modifications in the case of the polycrystalline technically pure copper. The EBSD, XRD, calorimetry and microhardness measurements were performed. Texture and mechanical characteristics were studied using a crystal deformation model and the finite element method. The latter calculations enable to optimize some parameters of asymmetric rolling process.

The qualitative and quantitative behavior of titanium T40 during tensile loading with a special emphasis on the presence of deformation twins in the observed microstructures is described. The samples for tensile tests were cut out from the rolled titanium sheet along the rolling and transverse directions. Several microstructure maps were determined using Electron Backscatter Diffraction technique (EBSD). These data were used to obtain crystallographic textures, misorientation distributions, grain size, twin boundary length, grain orientation spread, low and high angle boundary fractions and Schmid and Taylor factors. The deformation mechanisms and microstructure characteristics are different in the samples stretched along rolling and transverse directions. A strong appearance of tensile twins was observed in the samples deformed along transverse direction. On the other hand, more frequent subgrain formation and higher orientation spread was observed in the sample deformed along rolling direction, which caused’‘orientation blurring’ leading to an increase of grain size with deformation, as determined from OIM analysis.

With regard to medical applications, the need for producing high-strength titanium-based materials continues to rise due to the fact that pure titanium is characterized by low mechanical properties, yet remarkable corrosion resistance and biocompatibility. Microstructure-strength relationship for pure titanium (grade 2) fabricated by hydrostatic extrusion, an unconventional severe plastic deformation technique, has been quantified within the present study. X-ray powder diffraction, transmission electron microscopy and electron backscatter diffraction examinations were carried out as well as mechanical behavior was tested in order to find out which of the strengthening mechanisms contribute the most to the overall yield strength of the obtained material. Special emphasis has been put on grain refinement, grain boundary character and a few intragranular characteristics, indicating grain fragmentation. Applying multi-stage hydrostatic extrusion process to pure titanium resulted in fabricating the material that exhibits strong, fiber texture and non-homogeneous, ultrafine-grained microstructure with a host of structural defects in the form of dislocations and low-angle grain boundaries. The material tends to demonstrate remarkable mechanical properties, exceeding those of Ti-6Al-4V, yet its ductility is substantially lower. Based on the microstructure-property analysis it was found that the contribution of grain refinement and substructure evolution to the strength of the hydrostatically extruded titanium was of the highest significance.

Synchrotron X-ray diffraction was applied to study the evolution of lattice strain and stresses in both phases of pearlitic steel during a tensile test. The advantage of the methodology used in this work is the possibility of experimental study of stress localisation, which is directly determined from measurements and can be used to study the process of strain strengthening of lamellar pearlite. It was found that in the elastic range of deformation, both cementite and ferrite are loaded similarly due to the nearly equal elastic properties of both phases, while plastic deformation leads to significant load transfer from ferrite to cementite. Due to the complexity of the lamellar microstructure of the material, the classical elastic-plastic self-consistent model does not correctly predict the partitioning of the stresses between phases during plastic deformation. Therefore, the grain-matrix interaction given by the self-consistent model was modified and successfully applied to simulate the interaction between phases. The synchrotron experiment allowed us to determine the critical resolved shear stresses of ferrite phase in the pearlitic steel subjected to different thermal treatments. The role of cementite in material strengthening was evaluated on the basis of the evolution of von Mises stress, experimentally determined in both phases. It was found that during plastic deformations, the von Mises stress does not change significantly in ferrite compared to an important increase in elastically deformed cementite. Therefore, the partitioning of stresses between phases is mainly responsible for the strain strengthening of the tested pearlitic steel exhibiting fully lamellar microstructure.

Asymmetric rolling can be used in order to modify material properties and to reduce forces and torques applied during deformation. This geometry of deformation is relatively easy to implement on existing industrial rolling mills and it can provide large volumes of a material. The study of microstructure, crystallographic texture and residual stress in asymmetrically rolled titanium (grade 2) is presented in this work. The above characteristics were examined using the EBSD technique and X-ray diffraction. The rolling asymmetry was realized using two identical rolls, driven by independent motors, rotating with different angular velocities. It was found that asymmetric rolling leads to microstructure modification and refinement. At low deformations one observes a process of grain size decrease caused by the asymmetry of rolling process. In contrast, at the medium range of deformations the microstructure refinement consists mainly in subgrain formation and grain fragmentation. Another observation is that for low to intermediate rolling reductions (≤40%) the predominant mechanisms are slip and twinning, while for higher deformation (>40%) the main mechanism is slip. It was found that grain refinement effect, caused by the rolling asymmetry, persists also after recrystallization annealing. And finally, texture homogenization and reduction of residual stress were confirmed for asymmetrically rolled samples.

Texture evolution in commercially pure titanium deformed by equal-channel angular pressing (ECAP) and extrusion with forward–backward rotating die (KoBo) is studied both experimentally and numerically. New results are provided that demonstrate the effects of distinct and complex deformation paths on the texture in the ultra-fine grained (UFG) material obtained after severe plastic deformation (SPD). The numerical simulations are based on the self-consistent viscoplastic method of grain-to-polycrystal scale transition. A recently proposed modification of the probabilistic scheme for twinning is used that provides consistent values of the twin volume fraction in grains. The basic components of the experimentally observed texture are reasonably well reproduced in the modelling. The numerical simulations provide an insight into the internal mechanisms of plastic deformation, revealing substantial activity of mechanical twinning in addition to the basal and prismatic slip in titanium processed by ECAP.

The goal of the work was to study the asymmetric rolling process, especially the resulting textures formation, using the Finite Element Method (FEM) with implemented crystallographic deformation model. This implementation enabled the examination of deformation heterogeneity, taking into account the crystalline nature of the processed material. The asymmetric rolling process was also studied experimentally using the EBSD technique. Rolling asymmetry was realized using two identical rolls driven by independent motors, which ensured a controlled range of process asymmetry. We examined crystal deformation mechanisms, resulting texture and internal stress distribution in symmetrically and asymmetrically rolled polycrystalline titanium (grade 2). It was found that asymmetric rolling produces a homogeneous texture across the material thickness, contrary to symmetric rolling. The effects of texture modification, predicted in three sample layers, were compared with EBSD experimental results.

The multireflection grazing incident X-ray diffraction (MGIXD) is used to determine a stress gradient in thin surface layers (about 1-20 μm for metals). In this work two theoretical developments of this method are presented. The first procedure enables determination of c/a parameter in hexagonal polycrystalline materials exhibiting residual stresses. In the second method, the influence of stacking faults on the experimental data is considered. The results of both procedures were verified using X-rays diffraction.

Asymmetric rolling can be used in order to modify material properties and to decrease forces and torques applied during deformation. This geometry of deformation is relatively easy to implement on existing industrial rolling mills and it can provide large volumes of a material. The study of microstructure, crystallographic texture and residual stress in asymmetrically rolled titanium (grade 2) is presented in this work. The above characteristics were examined using EBSD technique and X-ray diffraction. The rolling asymmetry was realized using two identical rolls, driven by independent motors, rotating with different angular velocities w1 and w2. It was found that asymmetric rolling leads to microstructure refinement, texture homogenization and lowering of residual stress.

The crystallographic texture of metallic materials has a very strong effect on the properties of the materials. In the present article, we look at the rolling textures of fcc metals and alloys, where the classical problem is the existence of two different types of texture, the “copper-type texture” and the “brass-type texture.” The type of texture developed is determined by the stacking fault energy of the material, the rolling temperature and the strain rate of the rolling process. Recent texture simulations by the present authors provide the basis for a renewed discussion of the whole field of fcc rolling texture. We simulate the texture development with a model which allows us to vary the strength of the interaction between the grains and to vary the scheme for the calculation of the lattice rotation in the individual grains (type CL/MA or PR/PSA). For the deformation pattern we focus on {111} slip without or with deformation twinning, but we also consider slip on other slip planes and slip by par...

The results of three-dimensional simulation of asymmetric rolling, using Finite Elements Method, are presented. The example case of low carbon steel is considered. The rolling asymmetry, considered in the present work, results from different angular velocities of two identical working rolls. The effects of asymmetry on stress and strain distributions, material bending and variations of normal force and torque exerted by rolls are calculated and discussed. A special emphasis is done on the influence of inclined entry of a rolled material, which can appear in sequential rolling. Such the entry can partly compensate the material bending during. The results of the present simulations show that optimum parameters can be found in order to minimize the effect of sheet curvature and to reduce the applied torque and normal rolling force. The predicted internal stress distributions were applied next in the crystallographic deformation model; the predicted textures of symmetric and asymmetric rolling are in good agreement with experimental results.

The multi-reflection grazing incidence X-ray diffrection was used to determine residual stress gradient in the mechanically polished Al-Mg alloy and CrN coating. Also, the root mean square values of the third order lattice strain was determined using Wiliamson-Hall method. The results obtained for Al-Mg alloy show that the stress field in the surface layer as well as the microstructure (density of dislocation) depend strongly on the sample preparation. A very high residual compressive stress, which does not change significantly with depth, was measured in the CrN coating. Moreover, a large value of the measured third order strains in the coating was found.

The goal of this work was to study the asymmetric rolling process using the Finite Element Method (FEM) coupled with the deformation model of polycrystalline material. The Leffers-Wierzbanowski (LW) model was selected to be implemented into FEM. This implementation enables a study of heterogeneous plastic deformation process, like asymmetric rolling, taking into account its crystallographic nature. The asymmetric rolling was realized using two identical rolls, driven by independent motors, rotating with different angular velocities. This enabled to obtain a controlled range of rolling asymmetry. Our aim was to examine the properties of asymmetrically rolled commercially pure titanium (Grade 2).

Asymmetric rolling is a promising forming technique offering numerous possibilities of material properties modification and the improvement of technological process parameters. This geometry of deformation is relatively easy to implement on existing industrial rolling mills. Moreover, it can provide large volume of a material with modified properties. The study of microstructure, crystallographic texture and residual stress in asymmetrically rolled titanium (grade 2) is presented in this work. The above characteristics were examined using EBSD technique and X-ray diffraction. The rolling asymmetry was realized using two identical rolls, driven by independent motors, rotating with different angular velocities ω1 and ω2. This ensured a wide range of rolling asymmetry: A=ω1/ω2. It was found that a strong shear stress induced in the asymmetrically rolled material allowed to obtain a microstructure refinement, texture homogenization and lowering of residual stress.

The relation between residual stresses occurring in plastically deformed material and after subsequent annealing is of practical and theoretical importance. In the present work the X-ray multi-reflection method was applied to determine residual stresses and their orientation distribution in rolled and annealed ferrite and austenite steel samples. An important decrease of the first- and the second-order residual stresses was observed during recovery and recrystallization processes. Diffraction peak width was also studied and correlated with stress variation during annealing. Different kinetics of stress relaxation in ferrite and austenite were explained by different levels of stacking fault energy and different types of intergranular interactions occurring in these materials.

The aim of the present work is to study effects occurring during elatoplastic deformation and unloading of Al/SiCp metal–matrix composite material. We have measured lattice strains for both phases independently using two separated diffraction peaks (the 111 reflections of Al and SiC) during in situ tensile testing. Lattice strains were measured in the direction parallel to the applied load. The results were compared with an elastoplastic model in order to find parameters determining the plastic deformation of Al matrix (critical resolved shear stress and hardening parameter). We have found that during initial deformation relaxation of the thermal stresses occurs in both phases. Afterwards, the distribution of strains measured during the in situ test and unloading of the sample agree very well with self-consistent model prediction.

Rotation of grain crystal lattice is the basic mechanism of texture formation and of anisotropic behavior of metals during plastic deformation. The classical definition of crystal lattice rotation leads in some cases to different texture and residual stress predictions than the definition based on the orientation preservation of selected sample planes and/or directions. Also the intensity of grain-matrix interaction plays an important role in the prediction of the above quantities. These problems were studied using elasto-plastic deformation model of polycrystalline materials. Examples of austenite and ferrite steels were considered.

The geometry based on the multireflection grazing incidence X-ray diffraction (called the MGIXD method) can be applied to measure residual stresses. Using this method, it is possible to perform a non-destructive analysis of the heterogeneous stresses for different and well defined volumes below the surface of the sample (range of several mm). As the result the average values of stresses weighted by absorption of X-ray radiation are measured. In this work the stress profile as a function of depth for mechanically polished Ti and Al samples were calculated from MGIXD data using inverse Laplace transform.

Multireflection grazing incidence X-ray diffraction (MGIXD) was applied to measure residual stresses in thin surface layers and the problem of X-ray elastic constants (XEC) used for the interpretation of results was studied. To show the influence of the X-ray elastic constants on the interpretation of MGIDX results, polycrystalline materials having low (Ti alloy) and high elastic anisotropy of crystallites (Ni alloy) were investigated.

The main purpose of the present work is to describe the qualitative and quantitative behaviours of aluminium during high strain plastic deformation and the effect of deformation on the subsequent recrystallization process. An Electron Backscatter Diffraction analysis of aluminium after the Equal channel angular pressing (ECAP) and recrystallization process is presented. In order to do this, several topological maps are measured for samples processed by 4 and 8 passes and recrystallized. The processing was conducted with route C. For all samples, distributions of grain size, misorientation, image quality factor (IQ) and texture were preceded and then analysed in some detail.

The results of crystallographic textures and residual stress measurement in cross-rolled low carbon ferrite steel and polycrystalline copper of commercial purity are presented. It was found that cross-rolling significantly modifies crystallographic texture, residual stresses, and finally the plastic strain anisotropy. The cross-rolling provides a tool to modify the final properties of the material.

The texture (crystallographic texture) of a polycrystalline material is the statistical representation of the preferred orientation of the crystal lattices in the various grains. The great majority of the materials that we encounter do have a texture, some degree of preferred orientation of the crystal lattices, and this texture may have a strong effect on the properties of the materials. The texture is introduced by lattice rotations in the individual grains during processing. The present critical assessment deals with the lattice rotations during rolling of face centred cubic (fcc) metals and alloys. Sixteen years ago, a modification of the traditional procedure for the calculation of these lattice rotations was suggested, a modification that would permit a realistic modelling of the development of the brass type texture, one of the two types of texture developed during rolling of fcc materials. However, this modification was not given serious consideration by the texture community. Recently, tw...

International audience; Multi-reflection grazing incidence geometry, referred to as MGIXD, characterized by a small and constant incidence angle, was applied to measure low surface stresses in very thin layers of Al-Mg alloy and CrN coating. These two materials were selected in order to deal with the low and high levels of residual stress, respectively. The influence of different mechanical treatments on residual stresses was studied for Al-Mg samples. It was found that both rolling and mechanical polishing influence the distribution and amplitude of residual stress in surface layers. In the case of CrN coating, a very high compressive stress was generated during the deposition process. The stress distributions determined by the MGIXD method is in good agreement with the classic sin2 technique results for all studied samples. In performing stress measurements for a powder sample, it was found that the application of the Göbel mirror in the incident beam strongly reduces statistical and misalignment errors. Additionally, the root mean square values of the third order lattice strain within diffracting grains were determined.

Eight years ago recrystallization of OFE (oxygen-free electronic) copper was examined in detail using various techniques. In 2008 exactly the same material was measured using EBSD microscopy. The deformed state and fully recrystallized state have been analyzed and compared with data obtained eight years ago. The stored energy (SE) estimated by Image Quality (IQ) analysis was compared in these two cases. A significant amount of recovery took place in the sample, but only in some texture components. Some others present more or less the same SE as eight years ago. The textures of recrystallized samples were compared. We observed that the difference in SE distribution between the two deformed state has an influence on the final textures after recrystallization. Our study confirms the hypothesis that if a grain (orientation) has distinctly lower SE than other orientations - it has the highest growth preference (threshold hypothesis). Such grains (orientations) are dominant in the recrystallization texture.

The classical definition of lattice rotation leads in some cases to different textures than the definition based on the preservation of orientations of selected sample directions and/or planes. For example, if classical {111} slip is taken into account for f.c.c. materials, the former approach enables to predict both copper and brass types of rolling texture, while classical approach predicts only the first one. The analysis of rolling texture formation is done for two types of lattice rotation in function of grain-matrix interaction parameter used in a deformation model. Predicted textures and correlation factors estimating the similarity of predicted and experimental textures are presented.

Problem of Lattice Rotation Due to Plastic Deformation. Example of Rolling of f.c.c MaterialsRotations of grain crystal lattice are responsible for texture formation during plastic deformation. The classical definition of lattice rotation leads in some cases to different texture predictions than the definition based on the orientation preservation of selected sample directions and/or planes. For example, if classical {111} slip is taken into account for f.c.c. materials, the former approach enables to predict both copper and brass types of rolling texture, while classical approach predicts only the first one. The analysis of rolling process was done for two types of lattice rotation and in function of grain-matrix interaction parameter used in a deformation model. Correlation factors estimating the similarity of predicted and experimental textures as well as the shares of ideal orientations are discussed.

Formation of residual stresses and crystallographic textures during rolling have been studied using elasto-plastic deformation for polycrystalline material (Leffers-Wierzbanowski model). The rotation of grain crystal lattices is the basic mechanism of texture formation and anisotropic behavior of metals during plastic deformation. The classical definition of crystal lattice rotation leads in some cases to different texture predictions than the definition based on the orientation preservation of selected sample planes and/or directions (preservation condition). Also predicted residual stresses can be influenced by a choice of rotation definition. In the used deformation model of polycrystalline material, the intensity of grain-matrix interaction is described by the parameter L= aG, where G is shear modulus and a is elasto-plastic accommodation parameter. Model calculations have been done for different values of this parameter and for two definitions of lattice rotation. The predicted second order residual stresses and crystallographic textures for cold rolled ferrite steel are compared with experimental ones.

Grazing incidence geometry, called MGID-sin2y, was applied to measure surface stresses in very thin layers (depth of a few mm) of Al-Mg alloy samples subjected to different thermal and mechanical treatments. The Göbel mirror was used to parallelize the incident X-ray beam. Perfect collimation of the beam significantly increases accuracy of determined peak position and consequently allows to measure low stresses in surface layers.