Low-Temperature High-Frequency Induction Brazing of 5052 Aluminum Alloy to Stainless Steel with Sn-Zn Solder

Low-temperature high-frequency induction brazing of 5052 aluminum alloy to stainless steel was carried out using Sn-30Zn with reactive-flux 88ZnCl2-10NH4Cl-2NaF wt.%. The influence of processing parameters on microstructures, mechanical property and fracture behavior was investigated. Intermetallic compounds were not observed at the interface of the steel. The brazing seam consisted of Sn-Zn eutectic structures, Zn-rich solid solution and oxide inclusion. The diffusion of Sn and Zn into the aluminum grain boundary led to an intergranular penetration layer. When brazing at 370°C for 30 s, the joint fractured in the brazing seam and the shear strength reached the highest at 87 MPa. The fracture surface of the joint presented ductile characteristics. The diffusion of F− in the flux made the oxide film expand and crack. Zn2+ permeated through the crack of the film and then reacted with Al, which removed the film from aluminum substrate.