Observations were made of grain-boundary sliding along symmetrical tilt coincidence boundaries, S = 9 {11▪2}, and 3 boundaries which deviated at various angles from the coincidence misorientation in bicrystals. The coincidence boundary, and boundaries whose deviation did not exceed about 6º, slid and migrated in a coupled manner which was predicted by the DSC-dislocation model. A boundary whose deviation exceeded about 6º slid without migration, and with a significantly lower rate, than the other boundaries; apart from the coincidence one. Sliding along the coincidence boundary was activated at higher stresses only in the presence of intragranular slip. These results made it possible to distinguish special, near-special and general boundaries. It was emphasized that the ability of a boundary to slide and migrate in a fixed ratio was an important criterion for its uniqueness.

Sliding Characterization of Coincidence, Near-Coincidence and General Boundaries in Zinc. A.D.Sheikh-Ali, J.A.Szpunar: Materials Science Forum, 1999, 294-296, 645-8