On the contributions of diffusion and sliding to the overall strain of diffusional creep

Nabarro-Herring diffusional creep (DC) is of importance at low stresses and high temperatures in fine grained materials. In a previous analysis, the entire DC strain was considered to be arising from a single step of each of diffusion and sliding. It is more realistic to consider the overall strain of DC in terms of several infinitesimal steps of diffusion and sliding. Making use of a two-dimensional array of hexagonal grains and treating the DC as a multistep process involving discrete sliding and diffusion steps of varying number of magnitude, the relative contributions of the two processes are assessed as a function of total DC strain. Our analysis is further based on conservation of mass or area (two dimensional case) of grains and invariance of grain boundary angles because of deformation. (orig./MM)