Solute segregation in metals under irradiation

A kinetic model has been designed to study substitutional solute segregation during irradiation in facecentered-cubic metals. The model includes a split interstitial binding to impurities to second-neighbor distances, vacancy binding to impurities to first-neighbor distances, and the possibility of migration of the bound complexes. Also taken into account are the effects of vacancy and interstitial diffusional encounters with impurities and spatially independent reaction terms. The resultant rate equations have been solved numerically for a thin-foil geometry as a function of time for different temperatures, defect-production rates, internal sink concentrations, foil thicknesses, defect-impurity binding energies, and initial impurity concentrations. Using parameters appropriate for Zn in Ag, significant solute segregation is found in the temperature range from $0.2T_m$ to $0.6T_m$ ($T_m$ is the melting point). The temperature for maximum segregation is appreciably higher for heavy-ion bombardment or high-voltage-electron-microscope irradiation rates than for fast-reactor irradiation. The present calculations are intended to indicate the general pattern of segregation behavior and would be useful in areas of high-voltage electron microscopy, void formation, radiation-enhanced diffusion, and advanced materials development for nuclear-reactor applications.