A Novel Method for Resistance Plug Welding of 7075 Aluminum Alloy

This article investigates a novel resistance welding method – resistance plug welding – to weld 7075 aluminum alloy plates. Lap joints were made of two 1-mm thick 7075 aluminum alloy plates with circular holes punched in the center of the lap zone. A filler rod made of 5052 aluminum alloy, which has better resistance spot weldability, was inserted into the hole. The weld formation, microstructure, and mechanical properties of the joints were analyzed and compared with traditional resistance spot welding joints. The results showed that the current density was more concentrated during resistance plug welding (RPW), which led to larger nugget diameters and higher peak loads and energy absorption in a RPW joint. Defects such as hot cracking and pores, which form easily in 7075 RSW joints, were efficiently avoided in 7075 RPW joints because of the superior weldability of the 5052 aluminum alloy. Partial-thickness, pullout, and ductile fractures occurred in RPW joints, whereas interfacial fracture features and brittle fractures were observed in RSW joints.