Stress-driven migration of simple low-angle mixed grain boundaries

We investigated the stress-induced migration of a class of simple low-angle mixed grain boundaries (LAMGBs) using a combination of discrete dislocation dynamics simulations and analytical arguments. The migration of LAMGBs under an externally applied stress can occur by dislocation glide, and was observed to be coupled to the motion parallel to the boundary plane, i.e. tangential motion. Both the migration and tangential velocities of the boundary are directly proportional to applied stress but independent of boundary misorientation. Depending on the dislocation structure of the boundary, either the migration or tangential velocity of the boundary can switch direction at sufficiently high dislocation climb mobility due to the dynamics of dislocation segments that can climb out of their respective slip planes. Finally, we show that the mobility of the LAMGBs studied in this work depends on the constituent dislocation structure and dislocation climb mobility, and is inversely proportional to misorientation.