An investigation was made of the migration of a symmetrical tilt low-angle grain boundary under an applied shear stress in the presence of extrinsic dislocations. The results demonstrated that there was a threshold stress for the low-angle grain boundary to de-pin from extrinsic dislocations. Below the threshold stress, the low-angle grain boundary remained immobile at zero dislocation climb mobility while, for finite climb mobilities, it migrated at a velocity that was directly proportional to the applied stress, with a proportionality factor that was a function of misorientation, dislocation climb mobility and extrinsic dislocation density. Analytical expressions for the low-angle grain boundary mobility and threshold stress for de-pinning from extrinsic dislocations were derived. The analytical prediction of the low-angle grain boundary mobility was in excellent agreement with the simulation as well as experimental results. The implications of these results for understanding the migration of general grain boundaries were considered.

Low-Angle Grain Boundary Migration in the Presence of Extrinsic Dislocations. A.T.Lim, D.J.Srolovitz, M.Haataja: Acta Materialia, 2009, 57[17], 5013-22