It was recalled that, although general phenomenological relationships were available for interdiffusion, they were complicated, had few effective solutions and applied mainly to closed systems. Investigations of multi-component systems were thus usually limited to the determination of interdiffusion coefficients. Darken’s postulate, that the total mass flow was the sum only of diffusional and drift flows, was applied here to the description of diffusional transport in multi-component solid solutions. The equations of mass conservation, suitable expressions for the fluxes and the assumption of constant molar volume of the system permitted a complete quantitative description of diffusional transport in both open and closed systems under conditions where the diffusivities of the components varied with composition.

Interdiffusion in Multi-Component Systems Showing Variable Intrinsic Diffusivities. R.Filipek: Solid State Phenomena, 2000, 72, 165-70