The kinetics of the deformation that was caused by grain-boundary sliding and diffusion were considered for a 2-dimensional model polycrystal. It was shown that boundary sliding was a prerequisite for bulk diffusion. Sliding also had to occur concurrently with diffusion in order that a polycrystal should continue its diffusional creep. Rate equations for deformation of the polycrystal were also formulated for the case where both bulk and boundary diffusion operated in addition to boundary sliding. It was shown that the 2 diffusional processes were usually mutually exclusive. Only when the boundaries slid extremely fast, did the steady-state strain rate of the polycrystal become the simple sum of the strain rates due to bulk diffusion and to boundary diffusion.

Role of Grain-Boundary Sliding in Diffusional Creep of Polycrystals T.Mori, S.Onaka, K.Wakashima: Journal of Applied Physics, 1998, 83[12], 7547-52