Bulk diffusion-induced grain boundary migration due to elastic anisotropy

Grain boundary behavior in bicrystals with cubic symmetry during bulk diffusion of impurities from the surface was considered. These impurities act as a source of strains and corresponding internal stresses. Asymmetry of the grain boundary, a difference in the crystallographic orientation of the grains relative to the direction of diffusion, and the elastic anisotropy of crystals can lead to different stresses in the adjacent grains. The stress field for tilt and twist bicrystals was analyzed for the cases of diffusion along and perpendicular to the rotation axis. The anisotropy of stress relaxation (e.g. stemming from grain boundary sources of dislocations) was considered as an additional cause for a stress gradient across the grain boundary. The driving force for grain boundary migration due to bulk diffusion was determined through the difference between the coherency strain energies in adjacent grains. The driving force evaluated for parameters typical for metals turned out to be substantial as compared with the other known driving forces.