Influence of Filler Alloy on Microstructure and Properties of Induction Brazed Al/Cu Joints

This work aimed to clarity the influence of filler alloy on microstructures and properties of induction brazed Al/Cu joints. It was found that the alloying elements in the filler alloy changed the morphology and phase type of interfacial layer in the joint. Mg converted the native Al₂O₃ film into MgO and stopped the re-oxidation of aluminum. However, excessive Mg caused planar inter-metallic compounds (IMCs) to become wavy, which decrease the ductility of the joint. A suitable amount of Cu and Si removed residual oxide film and resulted in a thin planar IMCs layer, which is beneficial to Al/Cu joint. Al-8Si-4Cu-2Mg-1Ga-0.05Ce filler foil produced an excellent joint consisting of a 2μm Cu₉Al₄/CuAl₂ planar layer and free from oxide film. The tensile strength of the joint is higher than that of aluminum. The bend angle is higher 130°. The electrical resistivity of the joint is lower than the theoretical value.

Keywords:
Copper; aluminum; induction brazing; inter-metallic compound; filler alloy