Morphology and formation of Fe-Al intermetallic layers on iron hot-dipped in Al-Mg-Si alloy melt

We have examined the morphology and the growth of Fe-Al intermetallic layers of η-Fe2Al5 and θ-FeAl3 phases formed on pure Fe sheets dipped in an Al-8.2Mg-4.8Si (wt.%) alloy melt and pure Al melt at 750 °C. The η phase layer grows one order of magnitude slower in the Al-Mg-Si alloy melt than in the pure Al melt. The change in thickness of Fe sheets with dipping time is less pronounced in the Al-Mg-Si alloy melt than in a pure Al melt. Microstructure observations suggest that the retarded interfacial reaction between solid Fe and liquid Al-Mg-Si alloy is associated with a continuous θ phase layer formed in the Al-Mg-Si alloy melt, which acts as the diffusion barrier.