On the diffusion in the Mo–Ta refractory system

Abstract

Diffusion in the Mo–Ta system is studied as regards interdiffusion and impurity diffusion over the temperature range from 1500 to 1900 ° C . Interdiffusion coefficients, calculated with the den Broeder or Hall methods, are found to be weakly composition-dependent. Their temperature-dependence leads to Arrhenius parameters consistent with (i) literature data obtained at higher temperatures and (ii) a monovacancy mechanism. The composition-dependence of the Arrhenius parameters implies repulsive interactions between unlike atoms. Linear relationships between those parameters are found to exist among composition. Impurity diffusion coefficients D Mo(Ta) 0 and D Ta(Mo) 0 are determined by the Vignes and Birchenall method and are consistent with the interdiffusion coefficient limits. By comparison with literature data, anomalous behavior is obvious over the range 1500– 2220 ° C for both coefficients.