Process characteristics of the resistance heat-assisted ultrasonic seam welding of aluminum alloy and copper dissimilar metals

The 6061 aluminum alloy and pure copper with the same thickness of 1 mm were successfully welded with 1060 pure aluminum foil as the interlayer by resistance heat-assisted ultrasonic seam welding. The effect of resistance heat on the weld appearance, interface morphology, temperature field, and mechanical properties of the welded joints was investigated. The results showed that only local areas were connected at the interface of the Al/Cu welded joints by single ultrasonic seam welding and the tensile shear strength was only 45 MPa, which was attributed to the generated small welding energy in the welding process. However, the workpiece can be successfully preheated by the front resistance heat, which could soften the surface of the material in the resistance heat-assisted ultrasonic seam welding process. Therefore, an effective connection was formed at the joint interface under the function of the high-frequency vibration. Meanwhile, the interface temperature was significantly improved. The temperature at the Al/Cu interface was increased from 140 ℃ to 190 ℃, which increased the atomic diffusion distance at the Al/Cu interface, and the strength of the welded joint was significantly improved. The tensile shear strength reached 75 MPa, which was 67% higher than that of single ultrasonic seam welding.