The coalescence of dislocation loops by self climb

Abstract

During an isothermal anneal of an ion-bombarded UO₂ thin foil, electron microscope observations were made of the self-climb velocity of dislocation loops prior to coalescence. A model for loop movement by self-climb has been constructed and two interactions considered to act as the driving force. First, the mutual interaction of the loop strain fields, and second, the interaction between loops and individual vacancies. In the case of UO₂ the former predominates, but for metals both interactions are of similar magnitude. The model predicts that the loops remain circular during the climb process and that the velocity is rate controlled by the pipe diffusion coefficient at any particular temperature.