Analysis process of plasma arc melting brazing lap joint of dissimilar materials of aluminum and copper

LHM-200 plasma arc welding machine and the Zn-Al solder were used to melting braze dissimilar materials of T2 copper and LF6 rust-proof aluminum, the microstructure in the joint and the elementary composition in the interfacial are studied by using scanning electron microscope and energy spectrum analysis respectively. The results showed that, the technological parameters of welding process have a significant impact on the weld shape and joint mechanical properties. A reasonable process can obtain a satisfactory welded joints. The lap joint tensile shear strength was up to 175.5 MPa. Controlled plasma arc welding process can effectively control the brazing seam forming,and improve the joint performance. The best range of parameters for the welding current was 45~55 A, welding speed was 1.41~3.03 cm/s and plasma gas/protective gas flow rate was 0.2/0.75 L/min. The intermetallic compounds in the interface of copper and solder primarily are Al₂Cu and CuZn₂, and that in the interface of aluminum and solder is Al-Zn eutectic. In the middle of the solder is the black and white stripes organization, the black is Al-rich area, the white is Zn-rich area.