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Mécanismes de déformation des phases MAX : une approche expérimentale multi-échelle

Abstract : It is commonly believed that plastic deformation mechanisms of MAX phases consist in basal dislocation glide, thus forming pile-ups and walls. The latter can form local disorienta- tion areas, known as kink bands. Nevertheless, the elementary mechanisms and the exact role of microstructural defects are not fully understood yet. This thesis report presents a multi-scale ex- perimental study of deformation mechanisms of the Ti2AlN MAX phase. At the macroscopic scale, two kinds of experiments were performed. In-situ compression tests at room temperature coupled with neutron diffraction brought new insight into the deformation behavior of the different grain families in the polycrystalline Ti2AlN. Compression tests from the room temperature to 900 °C under confining pressure were also performed. At the mesoscopic scale, deformed surface micro- structures were observed by SEM and AFM. These observations associated with nanoindentation tests showed that grain shape and orientation relative to the stress direction control formation of intra- and inter- granular strains and plasticity localization. Finally, at the microscopic scale, a detailed dislocation study of samples deformed under confining pressure revealed the presence of dislocation configurations never observed before in MAX phases, such as dislocation reactions, dislocation dipoles and out-of-basal plane dislocations. In the light of these new results, mechanical properties of MAX phases are discussed.
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https://hal.univ-lorraine.fr/tel-03041098
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Submitted on : Friday, December 4, 2020 - 5:00:54 PM
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  • HAL Id : tel-03041098, version 1

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Antoine Guitton. Mécanismes de déformation des phases MAX : une approche expérimentale multi-échelle. Matériaux. Université de Poitiers (France), 2013. Français. ⟨tel-03041098⟩

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