DIFFUSION AND PHASE-DIAGRAM IN BINARY-ALLOYS

The relationship between diffusion and phase diagram is discussed in m ore detail for Ag-Au and Au-Ni alloys. For each alloy tracer diffusion and interdiffusion data have been compared with the corresponding pha se diagram. Tracer diffusion is related to the solid-liquid phase tran sition. Ag and Au tracer diffusivities D(x) in Ag-Au alloys and melti ng temperature T-m(x) of Ag-Au show opposite curvatures. The same hold s for D of Au and Ni in Au-Ni alloys and indicates a vacancy diffusio n mechanism. Interdiffusion depends on the critical temperature of the solid-solid phase transition of the phase diagram. The curvature of i nterdiffusivity D(x) is determined by the sign of T-c(x) or the intera ction energy epsilon of the regular alloy. The calculations agree well with the experimental data.