Weldability assessment of Al-SS dissimilar joints produced by ultrasonic spot welding route

Multiple materials are often used in the construction of modern vehicles to make them lighter and more affordable. Steel and aluminium alloys are the great building materials for these composite structures. Ultrasonic metal welding is an efficient solid-state joining technology that requires less energy and time than conventional welding methods while also eliminating the potential problems of distortion and shrinkage. In this research, stainless steel (UNS S30400) and aluminium (AA1100) sheets are ultrasonically welded with various surface treatments, including normally cleaned, electrolytically polished, and lubricated surfaces. The studies are carried out at various weld energies while maintaining constant vibrational amplitude and weld pressure parameters. The maximum lap shear and T-peel strength values are obtained as 621 N and 230 N at 2550 J of weld energy for the lubricated surface condition. According to the temperature profile, when weld energy grows, the weld interface temperature rises as well, reaching a maximum of 460 ˚C. It offers the perfect setting for the plastic flow phenomena to build strong bonds. The effects of natural aging and softening on the weld zone at each joint surface are studied through the microhardness test. Scanning electron microscopy and energy-dispersive X-ray spectroscopy investigations are also used to analyse fracture surfaces with various interface morphologies and characteristics.