An analytical solution of peritectic transformation kinetics

A simple diffusional analysis of peritectic transformation based on the lin earized concentration gradient approximation and utilizing overall/interfac ial mass balances has been presented. The predictions of the present model, as compared to those by the models proposed earlier, show a better agreeme nt with the experimentally determined kinetic data from the Cd-Ag system. H owever, the computed kinetics differ from the observed rates of transformat ion at a later stage (D(alpha)t/R-i(2) > 0.5), perhaps, due to the deviatio n of the cell geometry from the idealized configuration arising out of earl y impingement of diffusion fields and/or void formation in the liquid area. A systematic study on the effect of the relative widths of the concerned p hase fields on the transformation kinetics reveals that the secondary and ( primary + secondary) phase field widths exert appreciable influence on the rare of primary phase dissolution. However, the effect of concertration gra dient existing near the alpha - liquid interface on the latter is negligibl e. Finally, a dimensionless parameter (Phi) has been proposed to rationaliz e the process parameters and predict the kinetics of peritectic transformat ion with reasonable accuracy without resorting to lengthy calculations.