Numerical Simulation of Phase Transformation during Galvannealing Process

摘要

Many researchers have proposed the mathematical models to simulate galvannealing reactions, but none of them treated the growth of Fe-Zn alloys and the breakdown of Fe_2Al_5 separately. In the present work, we made the numerical model based on the simultaneous interdiffusion in the solid phase and at solid/liquid interface assuming the ratio of transformation being calculated by the difference of Gibbs free energy between two phases. First, the model was applied to simulate the galvannealing reaction in the Fe-Zn binary system to compare with the experiments where the steel sheets were immersed into the zinc bath without aluminum at 733K. The simulation results fit with the experiments in terms of the position and the order of formation for each Zn-Fe intermetallic phase, although the growth rates were somewhat less than that observed in the experiments. In addition, we have suggested one model combined the boundary model for the Fe_2Al_5 breakdown and the binary diffusional phase transformation model for the growth of Fe-Zn.