Microstructural Evolution and Mechanical Properties of Cu/Ti Joints Welded by Ultrasonic Spot-Welding with Zn Interlayer

Abstract

Cu/Ti dissimilar metals were joined together utilizing ultrasonic spot welding with a Zn interlayer. The threedimensional finite element analysis model was established to simulate the temperature field of the interface of Cu/Ti ultrasonic welding joint under different welding energies. The interface forming, microstructure, and mechanical properties of the Cu/Zn/Ti ultrasonic spot-welded joints were studied systematically. Results showed that the temperature distribution of the interface of the Cu/Zn/Ti ultrasonic welding joint was inhomogeneous, and the temperature of the interface below the indentation reached the highest and decreased gradually to the surrounding. With the increase of welding energy, the maximum temperature and the corresponding high-temperature region of Cu/Zn/Ti joint interface gradually increased. The interface of Cu/Zn/Ti ultrasonic welding joint was well formed, and the thickness was different, and the local position had wavy undulation morphology. When the welding energy was low, the interface microstructure was mainly composed of copper solid solution and titanium solid solution. As the welding energy increased, the microstructure of the joint interface was composed of CuZn compound, copper solid solution and titanium solid solution. When the welding energy was increased to 2000 J, the joint interface microstructure was composed of CuZn, Zn15Ti compound and copper solid solution. In comparison, Cu/Ti joints welded with a Zn interlayer in-between displayed the maximum shearing force about 33.5% greater than those of joints without a Zn interlayer.