Abstract
The automotive industry is striving to improve the fuel efficiency of internal combustion engine vehicles and extend the possible cruising range of electric vehicles, and reducing the weight of the vehicle body is an important issue. Aluminum alloys are being applied to panels and structural members as a means of reducing vehicle body weight. In addition, technologies have been developed to die-cast large parts in batches to achieve high composites and a reduction in the number of parts. It is required to join aluminum castings and rolled material by resistance spot welding, which is the most widely used joining technique in the automotive industry. However, aluminum castings have poor resistance spot weldability, and when joined with aluminum rolled material, there may be no penetration into the rolled material. In this study, the joint strength of resistance spot welded joints between castings and rolled aluminum alloy without penetration into the rolled aluminum alloy was measured, and the joining principle and strength development mechanism were investigated. The joint strength was measured by tensile shear test and cross-tension test, and the fracture morphology was observed. It was confirmed that the strength of the joint was comparable to that of spot-welded joints of rolled aluminum. Furthermore, cross-sectional observation and interfacial microstructural analysis revealed diffusion bonding between the molten α-Al of the casting aluminum alloy and the non-molten rolled aluminum alloy.
