Phase-field simulation of intergranular bubble growth and percolation in bicrystals

Three-dimensional phase-field simulations of the growth and coalescence of intergranular bubbles in bicrystal grain geometries are presented. We investigate the dependency of bubble percolation on two factors: the initial bubble density and the bubble shape, which is governed by the ratio of the grain boundary energy over the surface energy. The simulations show that variations of each of these factors can lead to large discrepancies in the bubble coalescence rate, and eventual percolation, which may partially explain this observed occurrence in experimental investigations. The results presented here do not account for concurrent gas production and bubble resolution due to irradiation, therefore this simulation study is most applicable to post-irradiation annealing.