Grain boundary dislocation geometry during diffusional creep

Abstract

Grain boundary dislocation curvatures are matched to the theoretically predicted stress distributions appropriate to diffusional creep. It is shown that below a critical value of stress, the curvature of the defect is such that it can completely prevent the processes of vacancy emission and absorption. At stresses greater than the critical value, continuous dislocation climb sources are able to operate. Calculations for a grain in the form of a right cylinder, undergoing grain boundary diffusion creep, show that the critical stress is 2U/bR, where U is the defect energy per unit length, b is the magnitude of the Burgers vector, and R the grain radius.

MST/414