Thermodynamic calculation of the Fe–Zn–Si system

Abstract

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, Γ 1, 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.