Research on Ultrasonic Welding of Ultra-Thin Copper and Stainless Steel Dissimilar Metals with Nickel Foil as Intermediate Layer

A high-power ultrasonic spot welding machine was employed to successfully weld T2 copper and 301 stainless steel dissimilar metals with nickel foil as intermediate layer. The influence of different welding energy on the interface temperature, cross-sectional macroscopic morphology, interface formation and mechanical properties of the joint was analyzed. The ABAQUS finite element numerical simulation software is used to analyze the temperature field of the interface under different welding energy. The study found that the peak temperature, high temperature residence time and the depth of indentation gradually increased with the increasing welding energy and the joint interfaces were relatively straight. There were three types of joint interfaces including copper/nickel, nickel/stainless steel and copper/stainless steel. Each interface department occured element inter-diffusion. There are diffusion layers. The maximum diffusion distances of copper-nickel elements and nickel-steel elements are 6.39 and 2.22 μm respectively. The maximum tensile shear force increases with the increase of welding energy and the maximum value was 1233.33 N. Welded joints fractured along the interface near the steel side of the base metal.