A numerical model of peritectic transformation

A rigorous numerical model of peritectic transformation kinetics based on t he solution of unsteady state diffusion equations in moving phase fields ha s been presented. The overall and interface mass balance equations are solv ed to calculate the rate of movement of the interfaces. The predictions of the present formulation show a better agreement with the experimental kinet ic data from the Cd-Ag and Pb-Bi systems, compared to those of the earlier proposed models based on quasi-static interface or quasisteady state approx imations. It is predicted that the presence of coring in the primary solid (beta) would not have any appreciable effect on the kinetics of peritectic transformation, especially, prior to the consumption of the liquid phase un less the product phase (alpha) has a restricted composition range. Furtherm ore, the kinetics remain practically unaltered irrespective of a linear or cored initial concentration gradient in the alpha-phase. However, the assum ption of a linear concentration gradient in a throughout the course of the transformation may significantly underestimate the kinetics. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.