Influence of diffusion brazing parameters on microstructure and properties of Cu/Al joints

The purpose of this article was to produce a sound Cu/Al joint by controlling interfacial inter-metallic compounds (IMCs) using suitable diffusion brazing parameter. An Al-8Si-4Cu-2Mg-1Ga-0.05Ce interlayer was used to diffusion braze copper to aluminum at a temperature above eutectic temperature and below melting point of aluminum under medium brazing pressure. The brazing pressure excludes eutectic structure and leaves a thin Cu9Al4/CuAl2 interfacial reaction layer in the joint. A short brazing time is enough to form a thin IMCs layer. However, increasing brazing time leads the rapid growth of CuAl2 and then results in some voids in the joint, which decreases the joint properties. It is not enough for a low brazing temperature to achieve a metallurgical bonding due to lack diffusion of atom. But, high brazing temperature results in excessive growth of IMCs, which is detriment to the bonding strength. The tensile strength and the bend ductility of Cu/Al joint diffusion brazed at 600 degrees C for 2 s under 9 MPa are equal to that of aluminum base metal and its conductivity is superior to that of aluminum base metal. Diffusion brazing with liquefaction in air can produce a sound Cu/Al joint both in mechanical and electrical properties.