VARIATION OF THE EFFECTIVE DIFFUSIVITY IN TWO- PHASE REGIONS

摘要

An equation was derived to calculate the effective diffusivity, [D~eff], in the two-phase region of a ternary alloy. The major assumption made was that the precipitate phase acts like a point source or sink of solute. The equation shows that [D~eff] is constant along a tie line when adjacent tie lines are parallel Then [D~eff] was calculated at 1200℃ in the γ + β region of the Al-Cr-Ni system and plotted as contours on the phase diagram. In order to determine the effect of [D~eff] variation on the modeling, a constant [D~eff] error function prediction of the diffusion path and concentration profiles was compared with a DICTRA finite difference simulation that accounts for diffusivity variations. Although the [D~eff] elements varied between 17 and 51, the difference between the predictions was negligible.