Coupling of grain boundary sliding and migration within the range of boundary specialness

Stress-induced behavior of high-angle near-coincidence symmetric tilt boundaries has been examined in bicrystal specimens of zinc. Parameters of coupling between boundary sliding and migration were determined. The angular deviation from the coincidence misorientation within the range of boundary specialness has a noticeable effect on the sliding-to-migration ratio, called “coupling factor”. Mechanisms of coupled boundary sliding and migration based on the motion of edge-type extrinsic and intrinsic grain boundary dislocations are discussed. It has been demonstrated that the observed alteration of the coupling factor with the change in boundary misorientation is due to the change of the parameters of extrinsic secondary grain boundary dislocations. The obtained results have also shown the limitation of the coincidence site lattice/displacement shift complete lattice model for the quantitative description of the structure of near-coincidence boundaries.