A rigorous numerical model of peritectic transformation kinetics based on the solution of unsteady state diffusion equations in moving phase fields has been presented. The overall and interface mass balance equations are solved to calculate the rate of movement of the interfaces. The predictions of the present formulation show a better agreement with the experimental kinetic data from the Cd-Ag and Pb-Bi systems, compared to those of the earlier proposed models based on quasi-static interface or quasi- steady state approximations. It is predicted that the presence of coring in the primary solid (β) would not have any appreciable effect on the kinetics of peritectic transformation, especially, prior to the consumption of the liquid phase unless the product phase (α) has a restricted composition range. Furthermore, the kin- etics remain practically unaltered irrespective of a linear or cored initial concentration gradient in the α- phase. However, the assumption of a linear concentration gradient in α throughout the course of the trans- formation may significantly underestimate the kinetics.
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