Formation behavior of Fe–Zn intermetallic layers at the interface between Fe–Mn and pure Zn melt at 460°C

The effect of Mn on the alloying reaction during hot-dip galvanization was investigated. The microstructure of the Fe–Zn intermetallic layers consisted of ζ, δ, and Γ phases for both pure Fe and Fe–2Mn (wt.%) alloy. The intermetallic layers grew thicker with increasing dipping time, and the growth rate of each layer was similar for both substrates. In the case of Fe–2Mn, the formation of the δ_1p phase was observed after dipping for 2 s. However, δ_1p formation was delayed for pure Fe, indicating that Mn may promote nucleation of the δ_1p phase. It is known that the δ_1p phase nucleates in the Fe-saturated ζ phase. The Fe content at the ζ/δ_1p interface was found to be lower for the Fe–2Mn alloy by electron probe microanalysis, suggesting that the supersaturation of Fe for the nucleation of δ_1p is decreased by Mn addition and Mn may stabilize the δ_1p phase. Once δ_1p became a continuous layer, the growth rates of the δ_1p layer on pure Fe and Fe–2Mn were similar. Mn could affect only the nucleation of δ_1p during the initial stage of the alloying reaction.