Carbon diffusivity in multi-component austenite

The diffusivity of carbon in multi-component austenite has been investigated using a thermodynamic-based analysis. The activity coefficient of carbon as a function of alloying elements and temperature was used to derive the carbon diffusivity as a function of composition and temperature. The strong influence of chromium (which decreases carbon diffusion rates) was incorporated in the diffusivity equation. The equation for carbon diffusivity was verified by comparing calculated results with measured diffusivity of carbon for various alloys.