Abstract:

In this paper, ultrasonic welding technology was applied for welding the Cu/Al dissimilar metals lap joints. The peak temperature, microstructure and mechanical properties of the joints were analyzed by UT-325 thermocouple thermometer, Optical Microscope (OM), Scanning Electron Microscopy (SEM) and universal testing machine. Results show that the stress at the Cu/Al interface increases constantly with the growing of welding energy, which causes the increase in interfacial friction and heat generation. Furthermore, the interface is improved gradually thanks to the increasing atomic activity and the plastic flow capacity. In addition, swirling deformation is formed at the interface due to the uneven distribution of stress. The driving force at the interface increases with the growing of welding energy that can cause a more obvious uneven distribution of the stress and a more dramatic swirling deformation. This kind of deformation will cause the mechanical interlock between Cu/Al dissimilar metals which can increase the shear force of the joint. The maximum shear force of the joint reaches 3.72 KN. Moreover, intermetallic layer with the dominant phase of Al2Cu is found in joints with the welding energy of 1700 J or even higher. Fracture mode of joints is the mixed-mode of ductile and brittle fractures.

Key words: material synthesis and processing technology, ultrasonic welding, Cu/Al dissimilar metals, stress distribution, swirling deformation, intermetallic layer