Interdiffusion in Multicomponent Systems

The phenomenological basis for the description of interdiffusion in multicomponent systems and the experimental approaches employed for the determination of interdiffusion fluxes, interdiffusion coefficients and zero-flux planes are briefly reviewed. Interdiffusion coefficients determined for β (bcc) Fe-Ni-Al alloys at 1000°C are presented and the development of zero-flux planes is illustrated with selected Fe-Ni-Al diffusion couples. A new analysis involving the concepts of average, effective interdiffusion coefficients and penetration depths for the individual components in a diffusion couple has been developed. Diffusion paths for a few interdiffusion experiments carried out in the Ti-Al-Nb system at 1100°C are also presented. A Ti-Al-Nb diffusion couple that developed B2 phase as a diffusion layer is analyzed for the determination of effective interdiffusion coefficients for the components over selected concentration ranges; these data are discussed in the light of ordering in the B2 phase.