Dislocation dynamics simulation of thermal annealing of a dislocation loop microstructure

Abstract

Thermal evolution and elevated temperature annealing of the dislocation microstructure of an irradiated metal, represented by an ensemble of elastically interacting interstitial dislocation loops, is explored using discrete dislocation dynamics simulations. The two fundamental microscopic processes driving the evolution of dislocations are the pipe diffusion of atoms along the dislocation lines, giving rise to the dislocation self-climb, and bulk diffusion of vacancies, resulting in the conventional dislocation climb. Simulations show that the coalescence and coarsening of the prismatic dislocation loop microstructure, observed at lower temperatures, is driven primarily by the dislocation self-climb. In tungsten, dislocation self-climb gives rise to a pronounced change in the dislocation loop microstructure at temperatures close to 800 °C, see Ferroni et al. (2015) [1], whereas a similar microstructural transformation of the dislocation network driven by self-climb in α-iron is predicted to occur at ∼270 °C. Simulations also show that the diffusion of vacancies in the crystal bulk is able to explain the observed annihilation rates of interstitial loops in tungsten.