Effect of Si on the Formation and Growth of Intermetallic Compounds at Roll-Bonded Aluminum–Steel (Al-St) Interface

The formation and growth of intermetallic compounds (IMC) were investigated using the Al-St clad materials with additional different Si content to aluminum and steel substrate by differential scanning calorimetry, scanning electron microscopy and energy-dispersive x-ray spectroscopy, x-ray diffraction and transmission electron microscopy. The addition of Si to Al (Al-0.8Si/St) can drastically delay the formation of IMC and accelerate the growth of IMC layer. The Si (Al-0.8Si/St) segregates at the interface and inhibits the diffusion of Al atom to steel before the IMC forms, which further decreases the diffusion depth of Al in the steel layer. By contrast, the addition of Si to St (Al/St-0.8Si) has limited impact on delaying the formation and decelerating the growth of IMC layer. The Si (Al/St-0.8Si) hardly affects the diffusion of Fe atom to the aluminum layer. Among the four clad materials, the major IMC layer (η-Fe₂Al₅) always exhibits the parabolic growth phenomenon. The addition of Si cannot influence the phase compositions of IMC at the interface between the η-Fe₂Al₅ layer and the aluminum. However, we observe an extra Fe-rich phase β₁-Fe₃Al at the interface between the Fe₂Al₅ layer and steel substrate in the Al-0.8Si/St clad material.