Precipitation kinetics of rare gases implanted into metals

A rate-theory approach is used to interpret observations on the precipitation of Kr, Xe, and Ar injected into Ni at temperatures between 25 and 560deg C. At temperatures of 400deg C or higher, the implanted Kr precipitates evolve into a bi-modal size distribution containing small solid precipitates and an additional population of larger, faceted bubbles. The calculations explore the dependence of the Kr bi-modal size distribution on the maximum size of the solid Kr precipitates and on the bubble mobility. The sensitivity of the calculated size distribution to gas-atom diffusivity and gas-bubble nucleation rate is also investigated. The analysis suggests that the swelling in these high gas production rate experiments is primarily gas driven, and that during the irradiation whereas the large bubbles move by surface diffusion, the small, solid Kr precipitates are immobile. The relevance of the Kr-Ni interaction on the solid Kr precipitate size cutoff, and differences in behavior between implanted Kr, Xe, and Ar are discussed. (orig.)