Coupled growth in directional solidification of peritectic alloys

The growth characteristic of peritectic alloy during directional solidification was analyzed theoretically and compared with the growth characteristic described in the classical eutectic coupled growth model (Jackson-Hunt model), and a superheating steady state coupled growth model for peritectic alloy was presented. The microstructures of Fe-Ni peritectic system with hypo- and hyper-composition directionally solidified were investigated at different temperature gradients and growth velocities. The results show that the strict coupled growth between primary and peritectic phases only takes place at the temperature higher than peritectic phase transformation temperature in steady state. The temperature of coupled growth of the two solid phases is really above the peritectic reaction temperature. The theoretical and experimental results are confirmed each other.