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

Abstract

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.