Tensile Fracture Behavior of Cu/Al Butt Friction Stir Welding: Role of Interface Morphology

Via friction stir welding, 5.0-mm-thick pure copper and aluminum 1050 plates were butt-joined. The tool offset was offset by 4.0 mm to the aluminum at the start and then linearly changed at the interface to the end of the welded line. The tensile response occurred between the copper and aluminum was sensitive to the tool offset. The tensile fracture occurred in three distinct regions along the welded path. At first, the joint fractured at the interface, then at the heat-affected zone on the aluminum side and finally adjacent to the interface on the aluminum side. The tensile strength was also sensitive to the tool offset and varied significantly along the welded path. Both the interface diffusion thickness and intermetallic layer were reduced gradually from the start to the end of the weld. The interface morphology played a critical role in the tensile fracture behavior of the joint.