Thermodynamic calculation of the Fe-Zn-Si system

Silicon in steel significantly affects alloy growth kinetics in the coating in general galvanizing, thereby changing the coating microstructure from the usual stratified Fe-Zn alloy layers to a mass of ζ crystallites surrounding by liquid zinc. The Zn-Fe-Si phase diagram and the relevant thermodynamic information have great importance for the galvanizing industry in developing remedies for this problem. In this work, the available information on the Fe-Zn-Si system, including all three binary systems was reviewed and re-evaluated, and ternary parameters were extracted from the available experimental data. By assuming all the binary intermetallic phases with the exception of the δ, Γ1, and Γ phases, have no ternary solubility, a thermodynamic calculation of the Fe-Zn-Si system was carried out, and relevant isothermal and isopleths sections were calculated. Its applicability in galvanizing industry was discussed. There is a good agreement between the calculated and the experimentally determined phase boundaries.