Effect of intermetallic compounds on the mechanical property and corrosion behaviour of aluminium alloy/steel hybrid fusion-brazed welded structure

Abstract

Al alloy/steel joint was produced by fusion-brazing welding with different heat inputs to obtain intermetallic compounds (IMCs) layer with different thicknesses. Following by enhancing heat input, not only the FeAl binary IMCs (Fe2Al5 and Fe4Al13) became thicker at the interface, the formation of Fe-Al-Si ternary IMCs, such as Fe2Al8Si, also became evident. Nevertheless, the joint strength was maintained at a high level. An increase of corrosion current density with three orders of magnitude was identified when the joint was welded under a high heat input (>632 J/cm) due to the appearance of enhanced tunnelling corrosion caused by ternary IMCs with weld seam. Binary IMCs became less corroded with the increase of heat input arising from the cathodic corrosion protection. Therefore, a low heat input should be utilised to preserve the corrosion resistance of the joint, while keeping its mechanical performance.