A model for radiation-induced segregation in fcc binary alloys

Abstract A model is presented for radiation-induced segregation (RIS) in a face-centered cubic (fcc) binary alloy containing A- and B-atoms. Assuming that the interstitial in an fcc crystal takes the configuration of the 〈100〉 dumbbell, three types of interstitial dumbbells, AA-, BB- and AB-type, are considered. The present model includes the diffusion and conversion of the three types of interstitial dumbbells via an interstitialcy migration, their recombination with a vacancy, and vacancy diffusion by position exchange with a lattice atom. The fraction of AA-, BB- and AB-type dumbbells is determined through the conversions, and the AB-type mixed dumbbell plays an important role in the determination of the segregation direction. When a large number of mixed dumbbells moves toward the sinks, enrichment of the lower concentration element occurs, because the AB-dumbbell includes the same number of A- and B-atoms. When mixed dumbbell migration is rare, on the other hand, the lower concentration element can be depleted, even if the self-interstitial dumbbell composed of that element moves more quickly. Consequently, the direction of RIS depends on the mobility of point defects as well as alloy compositions. When the RIS kinetics of a Cu Au alloy is calculated with the model, good agreement is obtained with experimental results.