Inhomogeneous nucleation and growth of cavities in irradiated materials

The origin of the effect of inhomogeneous swelling observed near grain boun daries in irradiated materials is examined taking into account both nucleat ion and diffusional growth of cavities, and the interaction of cavities wit h mobile interstitial clusters produced in collision cascades. The model sh ows the formation of a characteristic profile of inhomogeneous swelling tha t exhibits features similar to those observed experimentally. The rate of s welling is found to be strongly dependent on the size of cavities, with cav ities growing near the boundary being able to reach substantially larger si zes than those growing in the interior area of the grain. The distance,z* b etween the peak of swelling and the grain boundary scales with the density of cavities No as z*similar to N-0(-beta), where beta is close to 1/3.