A numerical model of peritectoid transformation

A rigorous numerical model of the diffusion-controlled peritectoid transfor mation based on the isoconcentration contour migration method is presented here. The model is capable of considering the concentration dependence of d iffusivity in the participating phases. The predictions from the model show an encouraging agreement with the experimentally determined peritectoid ki netics in the Zr-Al system and dissolution kinetics in the Ni-Mo diffusion couple. An extensive parametric study through the present formulation indic ates that the peritectoid kinetics may be considerably affected by the diff usivities and phase field widths (in the equilibrium diagram) of the concer ned solids. In this regard, the field width and diffusivity in the peritect oid phase appear to exert the most significant influence on the reaction ra te. The numerically calculated transformation kinetics have been effectivel y rationalized by means of two dimensionless parameters, phi(1) and phi(2), which are functions of the concerned phase field widths and diffusivity in the product phase. In addition, these parameters enable prediction of the minimum time required for the completion of peritectoid transformation with out going through any rigorous computation.