Kinetics of Solute-Enhanced Diffusion in Dilute Face-Centered-Cubic Alloys

Abstract

A theory of the effect of solutes on solvent self-diffusion in dilute fcc alloys is given, based on the model of nearest-neighbor interactions between solute impurities and vacancies. The parameters of the theory are the four vacancy-jump frequencies in the neighborhood of an impurity and the vacancy-jump frequency in the pure crystal. No assumptions are made about the relative magnitudes of these frequencies. This distinguishes the present theory from previous theories based on the same model. The theory is used to deduce for each of nine dilute Ag-based alloys sets of jump-frequency ratios (and corresponding impurity correlation factors) that are consistent with measured values of the solute enhancement coefficient and of the impurity diffusion coefficient. The desirability of isotope-effect measurements to determine the impurity correlation factors is emphasized.