Etudes de lien entre écrouissage/restauration et croissance de grains dans les polycristaux métalliques thermomécaniquement transformés

Abstract : For many decades, the role of grain boundaries in the plastic behavior of crystalline materials questions engineers, metallurgists, materials scientists. After the decisive progress in plasticity of individual crystals and for their collective behavior in aggregates, the complex effects of boundaries on the actual behavior are the remaining challenge to master. If boundaries can as well be considered as damage sites as strengthening network in a poly-crystalline structure, they always contribute greatly to the macroscopic properties of the latter. This work is a contribution to the study of the behavior of boundaries during thermomechanical treatments inducing mobility. We talk about migration.We studied the essential characteristics of the migration of grain boundaries from SIBM mechanism (Strain Induced Boundary Migration). The migration of grain boundaries under annealing after deformation was monitored in situ SEM. Microstructural changes are analyzed by SEM and AFM. The main strengths and characteristics contributing to the boundary migration are studied. For strengths, a migration diagram linking the displacements of grain boundaries to the curvature energy and the stored energy from plastic deformation allowed to assessing of the relevance of the usual expression for the migration driving force and to discussing possible adjustments. For characteristics, we confirmed the surface effect of the thermal grooving and the more intrinsic one of triple junctions on the mobility of grain boundaries.
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Bermane Beucia. Etudes de lien entre écrouissage/restauration et croissance de grains dans les polycristaux métalliques thermomécaniquement transformés. Mécanique [physics]. Université Sorbonne Paris Cité, 2016. Français. ⟨NNT : 2016USPCD071⟩. ⟨tel-02137490⟩

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