On the theory of dislocation loop nucleation in irradiated crystals

Abstract

The theory of dislocation loop nucleation in irradiated crystals is critically analysed and revised. The key parameters of the nucleation model are reassessed within the traditional (mean field) rate theory for irradiation defects. In the new approach, it is shown that at relatively low irradiation temperatures all interstitial loops are supercritical (due to the absence of a critical nucleus) and grow until they coalesce with other loops or with the dislocation network. In the transition temperature range, a large critical size of interstitial loops arises and the nucleation rate decreases significantly. At higher temperatures, all interstitial loops become subcritical and shrink, in qualitative agreement with experimental observations in irradiated steels. The vacancy loops are shown to be subcritical at all irradiation temperatures and thus shrink and disappear, in agreement with observations. To further improve the predictions of the nucleation theory, possible modifications of the mean field rate theory for irradiation defects are discussed.