Interface structure and bonding in abrasion circle friction stir spot welding: A novel approach for rapid welding aluminium alloy to steel automotive sheet

Aluminium alloy 6111-T4 and steel DC04 1 mm sheets have been successfully welded with a cycle time <1 s by “Abrasion circle friction spot welding”, a novel approach to joining dissimilar materials. This was achieved by using a probe tool translated through a circular path to abrade the steel sheet. It is shown that successful welds can be produced between these two weld members with a cycle time of less than one second, that exhibit very high failure loads and a nugget pullout fracture mode desired by industry. Transmission electron microscopy investigation of the joint interface revealed no intermetallic reaction layer. The weld formation mechanisms are discussed.