Grain boundary diffusion and mechanisms of creep of nanostructured metals

Comparative investigations of diffusion in coarse-grained (d = 20 mum), nanocrystalline (d = 0.04 mum) and nanostructured nickel (d = 0.3 mum) have been carried out in a temperature interval of 0.2-0.3 melting temperature. The reasons for difference of parameters of copper grain-boundary diffusion in the above materials are discussed. The effect exerted by grain boundary state and grain boundary diffusion fluxes of impurity on creep mechanisms of nanostructured nickel and copper in the temperature interval of 373-473 K have been studied. Significant change in the apparent creep activation energy under copper grain boundary diffusion fluxes is described as a consequence of different contribution of grain boundary sliding to overall deformation.