Effect of microstructure on the saturation of swelling in irradiated materials

The interaction of cavities with mobile interstitial clusters is believed t o be responsible for the saturation of swelling in irradiated materials. We show that the saturation limit depends on the microstructure of the materi al, and that the origin of the effect is associated with the violation of t he low-density approximation in the case of scattering of one-dimensionally moving interstitial clusters by grain boundaries. For large grains, swelli ng is enhanced near the boundaries, while for small grains swelling is maxi mum in the grain interior. The maximum size of cavities corresponding to th e saturation of swelling is found to be many times the mean-field estimate.