Inhomogeneous Swelling Near Grain Boundaries in Irradiated Materials: Cavity Nucleation and Growth Saturation Effects

Abstract

ABSTRACTThe effect of inhomogeneous nucleation and growth of cavities near grain boundaries illustrates the failure of the standard rate theory to describe the kinetics of phase transformations in irradiated materials under cascade damage conditions. The enhanced swelling observed near grain boundaries is believed to result from the competition between the diffusional growth of cavities and their shrinkage due to the interaction with mobile interstitial clusters. Swelling rates associated with the two processes behave in a radically different way as a function of the size of growing cavities. For a spatially homogeneous distribution of cavities this gives rise to the saturation of swelling in the limit of large irradiation doses.We investigate the evolution of the population of cavities nucleating and growing near a planar grain boundary. We show that a cavity growing near the boundary is able to reach a size that is substantially larger than the size of a cavity growing in the interior region of the grain. For a planar grain boundary the magnitude of swelling at maximum is found to be up to eight times higher than the magnitude of swelling in the grain interior.