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34 results on '"Bourgon, Julie"'

13. Deformation and fracture behavior of new strain-transformable titanium alloys: a multi-scale investigation

Author

VARENNE Chloé, PRIMA Frédéric, BROZEK Cédrik, BOURGON Julie, BESSON Jacques, and GOURGUES-LORENZON Anne-Françoise

Subjects
Engineering (General). Civil engineering (General), TA1-2040
Abstract

Titanium alloys possessing Twinning and Transformation Induced Plasticity effects show promising mechanical properties, particularly high ductility, hardenability, impact and fracture toughness. This work focuses on a strain-transformable, coarse-grained β-Ti-Cr-Sn alloy displaying TWIP effect. To account for the enhanced properties of this alloy, compared to more conventional β-Ti alloys, fracture and deformation features were correlated at different scales. Examinations evidenced a major role of twinning and, more generally, of plasticity-induced phenomena in the ductile fracture process. The resistance of this alloy to plastic deformation (work-hardening), and to crack initiation and propagation is interpreted in view of the progressive, multiscale twinning mechanisms that occur up to the very final stages of fracture.

Published
2020
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14. Microstructure, Mechanical Properties, and Thermal Stability of Al-Al 2 O 3 Nanocomposites Consolidated by ECAP or SPS from Milled Powders.

Author

Lacour-Gogny-Goubert, Antoine, Doquet, Véronique, Novelli, Marc, Tanguy, Alexandre, Hallais, Simon, Bourgon, Julie, Villeroy, Benjamin, and Massion, Roxane

Subjects
THERMAL stability, MICROSTRUCTURE, SLIDING wear, NANOCOMPOSITE materials, YIELD stress, POWDERS
Abstract

Ultrafine-grained Al matrix nanocomposites, reinforced with Al2O3 nanoparticles, were produced from milled powders, either by equal channel angular pressing (ECAP), at room or high temperature, with or without back pressure, or by spark plasma sintering (SPS). Their microstructures, mechanical properties (compression, hardness, and sliding wear), and thermal stabilities (thermally induced softening and cracking) were compared, and the advantages and limitations of each process discussed on a scientific but also practical point of view. For the most successful set of process parameters, the yield stress in compression reached 380 MPa, the hardness, HV = 139, remained stable up to 500 °C, and the resistance to sliding wear was comparable to that of Al 5083, and better than that of Al 7075-T6. While the samples consolidated at high temperatures (by ECAP or SPS) showed a good thermal stability, those consolidated by ECAP at room temperature were prone to thermally induced softening and cracking, which was related to trapped and pressurized gases. [ABSTRACT FROM AUTHOR]

Published
2023
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15. Bullet-Shaped Magnetite Biomineralization Within a Magnetotactic Deltaproteobacterium: Implications for Magnetofossil Identification

Author

Li, Jinhua, Menguy, Nicolas, Roberts, Andrew P., Gu, Lin, Leroy, Eric, Bourgon, Julie, Yang, Xin'an, Zhao, Xiang, Liu, Peiyu, Changela, Hitesh G, Pan, Yongxin, Li, Jinhua, Menguy, Nicolas, Roberts, Andrew P., Gu, Lin, Leroy, Eric, Bourgon, Julie, Yang, Xin'an, Zhao, Xiang, Liu, Peiyu, Changela, Hitesh G, and Pan, Yongxin

Abstract

Magnetite produced by magnetotactic bacteria (MTB) provides stable paleomagnetic signals because it occurs as natural single‐domain magnetic nanocrystals. MTB can also provide useful paleoenvironmental information because their crystal morphologies are associated with particular bacterial groups and the environments in which they live. However, identification of the fossil remains of MTB (i.e., magnetofossils) from ancient sediments or rocks is challenging because of their generally small sizes and because the growth, morphology, and chain assembly of magnetite within MTB are not well understood. Nanoscale characterization is, therefore, needed to understand magnetite biomineralization and to develop magnetofossils as biogeochemical proxies for paleoenvironmental reconstructions. Using advanced transmission electron microscopy, we investigated magnetite growth and chain arrangements within magnetotactic Deltaproteobacteria strain WYHR‐1, which reveals how the magnetite grows to form elongated, bullet‐shaped nanocrystals. Three crystal growth stages are recognized: (i) initial isotropic growth to produce nearly round ~20 nm particles, (ii) subsequent anisotropic growth along the [001] crystallographic direction to ~75 nm lengths and ~30-40 nm widths, and (iii) unidirectional growth along the [001] direction to ~180 nm lengths, with some growing to ~280 nm. Crystal growth and habit differ from that of magnetite produced by other known MTB strains, which indicates species‐specific biomineralization. These findings suggest that magnetite biomineralization might be much more diverse among MTB than previously thought. When characterized adequately at species level, magnetofossil crystallography, and apomorphic features are, therefore, likely to become useful proxies for ancient MTB taxonomic groups or species and for interpreting the environments in which they lived.

Published
2020

20. Bimetallic Cu–Rh Nanoparticles on Diazonium-Modified Carbon Powders for the Electrocatalytic Reduction of Nitrates

Author

Mirzaei, Peyman, primary, Bastide, Stéphane, additional, Aghajani, Atieh, additional, Bourgon, Julie, additional, Leroy, Éric, additional, Zhang, Junxian, additional, Snoussi, Youssef, additional, Bensghaier, Asma, additional, Hamouma, Ouezna, additional, Chehimi, Mohamed M., additional, and Cachet-Vivier, Christine, additional

Published
2019
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34. Design and tensile properties of a bcc Ti-rich high-entropy alloy with transformation-induced plasticity.

Author

Lilensten, Lola, Couzinié, Jean-Philippe, Bourgon, Julie, Perrière, Loïc, Dirras, Guy, Prima, Frédéric, and Guillot, Ivan

Subjects
SOLID mechanics, MATERIAL plasticity, PLASTIC crystals, ENTROPY, DEFORMATIONS (Mechanics)
Abstract

A new bcc Ti-rich high-entropy alloy (HEA) of composition Ti35Zr27.5Hf27.5Nb5Ta5was designed using the ‘d-electron alloy design’ approach. The tensile behavior displays a marked transformation-induced plasticity effect resulting in a high normalized work-hardening rate of 0.103 without loss of ductility when compared to the reference composition Ti20Zr20Hf20Nb20Ta20. In this paper, a detailed microstructural analysis was performed to understand the deformation process, revealing architectural-type microstructures and a high volume fraction (65%) of internally twinned stress-induced martensiteα″after mechanical testing. This study opens the way to mechanical properties optimization and enhancement of titanium-based HEAs by combining multiple alloying designs. IMPACT STATEMENT For the first time, proof is given that transformation-induced plasticity was triggered in a bcc refractory high-entropy alloy, leading to a twofold increase in the normalized work-hardening rate. [ABSTRACT FROM PUBLISHER]

Published
2017
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