Simulation of migration and coalescence of helium bubbles in nickel

The mechanism of migration and coalescence of nanoscale helium bubbles was studied using molecular dynamics. Small helium bubbles in nickel were observed to migrate in a random-walk style at temperatures higher than 0.7 T-m (melting point). Coalescence occurred when two helium bubbles approached each other, leading to the formation of a large bubble. The motion of the helium bubbles in nickel proceeds by displacement of nickel atoms on the surface, which causes the rearrangement of other nickel atoms, resulting surface diffusion. These findings indicate that migration and coalescence may be the possible growth mechanism for small helium bubbles in nickel at high temperature. (C) 2019 Published by Elsevier B.V.