Grain-size dependent accommodation due to intragranular distributions of dislocation loops |
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Authors: | T Richeton S Berbenni M Berveiller |
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Affiliation: | Laboratoire de Physique et Mécanique des Matériaux, LPMM, UMR CNRS 7554, Arts et Métiers Paristech 57078 Metz Cedex 03, France |
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Abstract: | A grain-size dependent accommodation law for polycrystals is deduced from an inclusion/matrix problem (i.e., each grain is seen as embedded in a homogeneous equivalent medium) where plastic strain inside the inclusion is given as a discrete distribution of circular coaxial glide dislocation loops. The loops are assumed constrained at spherical grain boundaries. From thermodynamic considerations specific to a process of identical plastification in all the loops (considered as “super-dislocations”), an average back-stress over the grain is derived. In order to compute the very early stages of plastic deformation in a face-centred cubic polycrystal, this back-stress is incorporated into a diluted model in terms of concentration of plastic grains. Contrary to conventional mean-field approaches, a grain-size effect is obtained for the initial overall strain-hardening behaviour. This size effect results from an intrinsic contribution of intragranular slip heterogeneities on the kinematical hardening. |
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