New evidence for the formation and growth mechanism of the intermetallic phase formed at the Al/Fe interface

To clarify the underlying mechanism of formation and growth of aluminum coating, the interface microstructures of as-prepared aluminum coating iron were investigated using various experimental methods. The liquid Al–Si, Al–Ge alloys were chosen as the dipping baths. In both cases, the total thickness of the reaction layer is controlled mainly by the well-known diffusion growth of η-Al5Fe2. The melt environment of the Al bath plays a decisive role in the formation and growth of the diffusion layer. The results show that Ge atoms could also decelerate reaction layer growth like Si atoms, which mainly restrain the diffusion of Al atoms. Meanwhile, Ge element represents an abnormal concentration gradient in the η-Al5Fe2phase. The diverse growth behavior of the diffusion layer is attributed to the strong controlling role of the alloying element in Al baths based on the atomic diffusion and activity analysis.