Dissimilar joining of Al/SS sheets with interlayers by ultrasonic spot Welding: Microstructure and mechanical properties

Abstract

Ultrasonic spot welding (USW) has received a great deal of attention by the automobile manufacturer to build lightweight structural components. However, the versatility of using this process is still limited due to the substantial instabilities in weld quality. These fluctuations are mainly due to the lack of scientific understanding of this process and poor control of intermetallic compound formation. Therefore, this study is focused on the improving of the joint strength and its quality by ultrasonic welding of Al3003 and SS304 sheets with molybdenum (Mo) and zinc (Zn) powder as interlayers. The results revealed that the optimum thickness for Mo and Zn interlayers are found to be 0.11 mm and 0.15 mm, respectively. In comparison, Al3003/SS304 joints with Zn interlayer exhibits the maximum tensile shear failure load about 626.44 N at 1.5 s of weld time, which is better than those of the joints produced with Mo interlayer. The microstructural morphologies at the weld interface reveal the different characteristics like mechanical interlocking at the outside zone of the sonotrode knurl indentation, wavy type region under the sonotrode knurl, and swirling like diffusion zone inside the sonotrode knurl.