Coalescence of helium bubbles in aluminum

The formation and coalescence of helium bubbles in aluminum with annealing at 550°C is examined experimentally using electrical resistivity and electron microscopy. Results for the kinetics of coalescence are compared with those obtained by computer simulation in order to test models based upon various mechanisms for bubble motion. The computer method previously developed is extended from an ideal to a Van der Waals gas and effects due to the surface energy of aluminum are considered. Comparison of experimental and computer results indicates that the motion of helium bubbles in aluminum is not surface-diffusion limited and that it is consistent with the facet nucleation-limited mechanism originally proposed by Willertz and Shewmon.