On density effects in point defect solutions under irradiation. II. Formation of interstitial dislocation loops

Abstract

The chemical potential approach, making it possible for one to account for density effects in supersaturated solution of point defects, is applied to consideration of interstitial loop formation kinetics in metals under homogeneous irradiation. Quasi-chemical rate equations are reformulated in terms of chemical potential, rather than in terms of concentrations of species involved in reactions, following a procedure known in the theory of irreversible processes. The extension of rate equations is tested on a simpler model of bimolecular reactions. Then the density effect, such as radiation induced spontaneous clustering of interstitials, is investigated in irradiated metals on the background of interstitial loop formation as described by conventional rate equation solution. The phenomenon, that reveals itself by spontaneous formation of di-interstitials, would be expected to become noticeable at irradiation temperatures about 0.25 to 0.3 of the absolute melting temperature if the rate of defect generation is high enough. For a steady-state solution analyzed, the density effect brings about the higher number density of forming interstitial loops with reduced mean dimensions if compared with conventional based consideration. Possibilities of experimental investigations of the proposed mechanism of interstitial loop formation are discussed.