Diffusion and conversion of interstitial dumbbells in segregated ternary alloys under irradiation

A radiation-induced segregation model for concentrated alloys based on the inverse Kirkendall effect is successfully used to predict element segregation in model alloys under irradiation conditions. In this model the segregation is the result of preferential atom-vacancy jumps. But under conditions of high irradiation flux or wide temperature range, a description of interstitial migration must be included in the model. In the present work the rate theory was used to simulate radiation-induced segregation near the grain boundary in Fe–Cr–Ni alloys. A model of diffusion and conversion of a mixed interstitial dumbbell was applied to describe the flux of interstitial. Six types of interstitial dumbbells and their conversion by a jump of one of its constituent atoms to a neighbouring site to form a dumbbell of different orientation, were considered. The vacancy flux was described similarly to the Wiedersich–Okamoto–Lam model, considering its migration through position exchange with a lattice atom.