Contribution of Interstitial Migration to Radiation-Induced Segregation in FCC Binary Alloys

The role of interstitials in the radiation-induced segregation (RIS) process in a face-centered cubic (fcc) binary alloy is investigated with a newly developed model. The model considers three types of interstitial dumbbells, their diffusion and conversion via an interstitialcy migration, recombination with a vacancy, and vacancy diffusion through the position exchange with a lattice atom. Analysis of RIS kinetics in the Cu-Au alloy is used to verify the model, and good agreement is obtained with experimental measurements. The relationship is examined between the present model and the Wiedersich-Okamoto-Lam model (WOL model) in which the mixed dumbbell movement is neglected. Effective diffusion coefficients are derived which incorporate the effect of the mixed dumbbell into the WOL model formulation.