A numerical model of peritectoid transformation

A rigorous numerical model of the diffusion-controlled peritectoid transformation based on the isoconcentration contour migration method is presented here. The model is capable of considering the concentration dependence of diffusivity in the participating phases. The predictions from the model show an encouraging agreement with the experimentally determined peritectoid kinetics in the Zr-Al system and dissolution kinetics in the Ni-Mo diffusion couple. An extensive parametric study through the present formulation indicates that the peritectoid kinetics may be considerably affected by the diffusivities and phase field widths (in the equilibrium diagram) of the concerned solids. In this regard, the field width and diffusivity in the peritectoid phase appear to exert the most significant influence on the reaction rate. The numerically calculated transformation kinetics have been effectively rationalized by means of two dimensionless parameters, φ₁ and φ₂, 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 without going through any rigorous computation.