Abstract:The effect of Si on the growth kinetics of intermetallic compounds during the reaction of solid iron and molten aluminum was investigated with a scanning electron microscope coupled with an energy dispersive X-ray spectroscope, and hot-dip aluminized experiments. The results show that the intermetallic layer is composed of major Fe₂Al₅ and minor FeAl₃. The Al-Fe-Si ternary phase, τ₁/τ₉, is formed in the Fe₂Al₅ layer. The tongue-like morphology of the Fe₂Al₅ layer becomes less distinct and disappears finally as the content of Si in aluminum bath increases. Si in the bath improves the prohibiting ability to the growth of Fe₂Al₅ and FeAl₃. When the contents of Si are 0, 0.5%, 1.0%, 1.5%, 2.0% and 3.0%, the activation energies of Fe₂Al₅ are evaluated to be 207, 186, 169, 168, 167 and 172 kJ/mol, respectively. The reduction of the activation energy might result from the lattice distortion caused by Si atom penetrating into the Fe₂Al₅ phase. When Si atom occupies the vacancy site, it blocks easy diffusion path and results in the disappearance of tongue-like morphology.

Key words: intermetallic compound; Fe-Al system; growth kinetics; activation energy; Si; hot-dip aluminizing; diffusion reaction