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Alliages à grains ultrafins et bimodaux : approche couplée expérience-modélisation basée sur la microstructure

Abstract : This work is focused on the elaboration and the mechanical behaviour of 304L and 316L austenitic stainless steel alloys with bimodal grain size distribution. The complementary approach between experiments and modelling enables a better understanding of both macroscopic and local mechanical responses and also of the associated deformation mechanisms.The use of two elaboration routes and optimized process parameters results in a wide range of samples with different bimodal grain size distributions. Grain sizes and fractions of each population are modified in order to study the influence of these microstructural characteristics on mechanical behavior. Uniaxial tensile tests are used to realize a database of mechanical properties of bimodal alloys and loading-unloading tests provides valuable informations about deformation mechanisms in these materials. With coarse grains (CG) embedded in an ultrafine grained (UFG) matrix, a relaxation of a part of the internal stresses seems to take place and leads to a delayed embrittlement of bimodal alloys as compared to their unimodal counterparts. Full-field modelling, based on two crystal plasticity laws with an explicit account of an internal length, is proposed. It constitutes a valuable prediction tool of effective properties of bimodal alloys in order, in particular, to study the effect of several microstructural characteristics. An access to local fields is also possible and tend, so far, to show similar results compared to experimental ones : stress relaxation is observed in the UFG matrix as well as stress concentrations at the CG/UFG interfaces.
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Submitted on : Friday, December 7, 2018 - 12:03:13 PM
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  • HAL Id : tel-01947917, version 1

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Baptiste Flipon. Alliages à grains ultrafins et bimodaux : approche couplée expérience-modélisation basée sur la microstructure. Mécanique [physics.med-ph]. Normandie Université, 2018. Français. ⟨NNT : 2018NORMIR06⟩. ⟨tel-01947917⟩

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