An equation was derived for the calculation of effective diffusivities in the 2-phase region of a ternary alloy. The main assumption made was that the precipitate phase acted as a point source or sink of solute. The equation showed that the effective diffusivity was constant along a tie-line when adjacent tie-lines were parallel. The effective diffusivity was calculated at 1200C (γ+ß region) for the Al-Cr-Ni system and was plotted as contours on the phase diagram. Errors in the assumed effective diffusivity had a negligible effect upon the predictions.

Variation of the Effective Diffusivity in Two-Phase Regions. H.Chen, J.E.Morral: Acta Materialia, 1999, 47[4], 1175-80