On the nature of void swelling

In this contribution we considered the nucleation and growth of vacancy clusters in nickel. All the molecular dynamics calculations were done with the help of one and the same interatomic potential found on the basis of the pseudopotential theory. We studied influence of alloying elements (tungsten, scandium) on trapping and mobility of vacancies and bivacancies, and calculated binding energies. It was found that different types of vacancy clusters (stacking fault tetrahedra, dislocation loops and voids) can be analyzed quantitatively with the help of simple geometrical principles. Swelling mechanism for irradiated metals, which is based on the peculiarities of void growth discovered by computer simulations, is proposed. The mechanism incorporates four postulates which explain why pure metals swell at all, why there exists incubation time for swelling, and why swelling is proportional to irradiation time to some power m, where m is at first larger and then smaller than one. The estimates give m ≅ 1.87 at the first stage and m=1/3 at the last one.