Dissimilar Joining by Ultrasonic Welding

Abstract

Ultrasonic welding is a rapid process for thin sheet joining. The authors wanted to show the aluminum-copper dissimilar joining by the ultrasonic welding process in this work. Ultrasonic welding is a suitable and straightforward process to establish dissimilar joints between different metals. The goal was to investigate the ultrasonic welding complex effect on the material properties. Ultrasonic welding is solid-state welding, which uses pressure, friction, ultrasound effect to establish a metallic joint. The complex effects are the friction heat, the pressure caused plastic deformation, and the ultrasound caused softening and hardening. The welding process used three kinds of geometry were, with 5 mm, 10 mm, 15 mm wide, and 80 mm length test samples. The welding is made by an ultrasonic welder machine (Branson Ultraweld L20 Spot Welder). The used parameters were the same, and the ultrasound frequency was 20 kHz. The welded spot area depended on the test sample size and the anvil sizes (12 mm x 14 mm). A microhardness tester tested the joint and the hardness of the heat-affected zone (HAZ). The hardness after the welding process showed a difference from the original hardness value of the metals. The measured results tendency is according to the literature. The ultrasound effect can cause crack propagation in the welded sheet. It was detected based on the tests that the hardness in the joint and the heat-affected zone shows differences as a function of the test sample sizes. Also detected that the crack inclination is stronger in the case of the wider sheets whiles having a bigger welded spot area. Based on the research result, it can conclude that the ultrasonically welded aluminum sheet's mechanical properties depend on the welding parameters and the welded material geometry. The results are in harmony with ultrasound softening and hardening effects theories.