Interface controlled diffusional creep

Abstract

Diffusional flow of a polycrystal is classically treated as a continuum diffusion problem: its rate is calculated by solving for the diffusional flux of matter through or around each grain in a polycrystal, driven by the stress acting on it. Many, but not all, experimental observations are adequately explained by this model. Progress in understanding the discrepancies can be made by considering the microscopic processes involved in diffusional flow: the detailed nature and number, of sinks and sources in the grain boundaries; and their mobility. This paper treats these problems and derives expressions for the rate of diffusional flow when the density of sinks and sources becomes small and when their mobility is limited by impurities, solutes, or precipitates. The results become identical with those of the classical treatment in the appropriate limits.