Grain boundary inclination dependence of GN dislocation patterns and density in bicrystal model

Abstract

Deformation behaviors of polycrystalline metals are quite complex, and we are not easy to directly investigate them; thus, analyses employing simple models such as bicrystals are required. In this study, we conducted crystal plasticity analysis of unidirectional tensile tests, using compatible-symmetric-type bicrystal models with the not-inclined grain boundary and incompatible-type bicrystal model with the inclined grain boundary; we investigated changes in patterns of geometrically necessary dislocation (GND) bans and the density of GNDs in the initial deformation. In the condition where the grain boundary contacted with the constrained faces, GND bans were formed and the distribution was changed with changing the inclination angle α of the grain boundary. In contrast, GNDs were not localized in high density in the condition where the grain boundary contacted with the free surfaces; the changes were caused by two-reasons: one was changes of compatibility of the bicrystal model with changing the inclination angle α, and the other was that deformation shapes of the bicrystal model under tensile loading were changed with changing the inclination angle α and the deformation was constrained by the constrained faces. The compatibility of and average density of GNDs in the bicrystal model could be estimated using differences of components of Schmid tensors between the crystal grains.