Based on the study of grain-boundary internal friction, it was demonstrated that the temperatures of onset and intensive development of true grain-boundary sliding (grain-boundary microsliding) as well as the activation energy of this process in submicrocrystalline and nanocrystalline metals and alloys with imperfect grain boundaries relative to coarse-grained ones with perfect grain boundaries decreased. For all of the grain structures studied, the activation energy of grain-boundary internal friction was found to exceed the respective one for grain-boundary diffusion but to be lower than the activation energy of bulk diffusion. The diffusion-controlled mechanism of true grain-boundary sliding was validated.

Diffusion-Controlled True Grain-Boundary Sliding in Nanostructured Metals and Alloys. E.F.Dudarev, G.P.Pochivalova, Y.R.Kolobov, E.V.Naydenkin, O.A.Kashin: Materials Science and Engineering A, 2009, 503[1-2], 58-61