Effects of composition and grain size on the interdiffusional behaviour in B2-RuAl intermetallic compound

Compositional as well as grain size effects on the interdiffusional behaviour in single-phase B2-RuAl intermetallic compound were studied in the temperature range between 1473 and 1773 K. Variations in the diffusion coefficient due to composition changes were investigated using a diffusion couple technique. Boltzmann-Matano analysis and numerical finite difference calculations were performed and the influence was determined to be a factor of five between the end compositions. Contribution of grain boundary diffusion on the measured coefficients at the lower temperatures has to be assumed due to grain sizes of about 5 μm. Using Hart's relation a range of grain boundary interdiffusion coefficients was suggested.