Radiation-induced solute segregation

Substitutional solute segregation in a face-centered-cubic metal under irradiation has been studied using a kinetic model. The model includes the effects of vacancy and dumbbell-interstitial diffusional encounters with solute atoms, diffusion of point defects and bound complexes, and spatially independent reaction terms. The GEAR package of subroutines, developed at Lawrence Livermore Laboratory, has been used for numerical solution of the resultant rate equations. Assuming thin-foil geometry and parameters appropriate for Zn in Ag, solute segregation is found to be significant in the temperature range from 0.2 to 0.6 T/sub m/, with maximum segregation occurring at approximately 0.45 T/sub m/. The temperature for maximum segregation is appreciably lower for reactor irradiation rates than for ion-bombardment or high-voltage electron-microscope irradiation rates. Segregation is also found to be maximum when the interstitial-solute binding energy is sufficiently high so that the migration energies of the vacancy and interstitial-solute complex become comparable