Angular Distribution of Slip Steps by Three-Dimensional Polycrystalline Model for Stainless Steel

Abstract

Localized deformation plays an important role in the initiation of irradiation-assisted stress corrosion cracking, and it can be characterized by the spacing and inclination of slip steps observed on the surface. In order to examine the contribution of mechanical factors (stress) to slipping, the angular distribution of slip steps was evaluated by using a three-dimensional polycrystalline model generated by Voronoi tessellation. An elastic finite element analysis was performed to derive the resolved shear stress (RSS) acting on each slip system. Random crystallographic orientations assigned to each grain caused the microstructural inhomogeneity of local stress due to anisotropic elastic properties. The angular distribution obtained was compared with the experimental results observed in irradiated and deformed stainless steel. It was shown that mechanical factors dominate the slipping behavior of the irradiated stainless steel and that not only RSS but also normal stress acting on the slip plane affects the crystallographic slip. The angular distribution was also evaluated from the maximum Schmid factor of individual grains, in which the inhomogeneous local stress was not taken into account. The angular distributions obtained using RSS and the Schmid factor were almost the same. This suggests that the inhomogeneity of local stress negligibly affects the angular distribution of slip steps, although the change in the local stress in the polycrystalline material is significant.