Diffusion-controlled true grain-boundary sliding in nanostructured metals and alloys

Based on the study of grain-boundary internal friction, it has been 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 decrease. For all grain structures studied the activation energy of grain-boundary internal friction is 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 is validated.