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 δ1p phase was observed after dipping for 2 s. However, δ1p formation was delayed for pure Fe, indicating that Mn may promote nucleation of the δ1p phase. It is known that the δ1p phase nucleates in the Fe-saturated ζ phase. The Fe content at the ζ/δ1p 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 δ1p is decreased by Mn addition and Mn may stabilize the δ1p phase. Once δ1p became a continuous layer, the growth rates of the δ1p layer on pure Fe and Fe–2Mn were similar. Mn could affect only the nucleation of δ1p during the initial stage of the alloying reaction.