Diffusion and phase diagram in binary alloys

Abstract

The relationship betwwen diffusion and phase diagram is discussed in more detail for AgAu and AuNi alloys. For each alloy tracer diffusion and interdiffusion data have been compared with the corresponding phase diagram. Tracer diffusion is related to the solid-liquid phase transition. Ag and Au tracer diffusivities D∗(x) in AgAu alloys and melting temperature T m( x) of AgAu show opposite curvatures. The same holds for D∗ of Au and Ni in AuNi alloys and indicates a vacancy diffusion mechanism. Interdiffusion depends on the critical temperature of the solid-solid phase transition of the phase diagram. The curvature of interdiffusivity D( x) is determined by the sign of T c( x) or the interaction energy ε of the regular alloy. The calculations agree well with the experimental data.