Joining of 7xxx high strength Al to casting Al alloys by friction self-piercing riveting process

Recently, casting aluminum (Al) automotive body structure has several benefits, such as lightweight, flexibility of design shape, improving productivity and suitable for mass production. Casting structure can be integrated into other Al body structures for safety and performance requirements. However, both casting Al and high strength 7xxx Al has low ductility at room temperature. For this reason, Conventional mechanical fastening techniques, such as self-piercing riveting, face limitations in dissimilar joining of casting Al and extruded Al at room temperature, often leading to cracking issues. To address above issue, a novel friction based self-piercing riveting process has been developed. This innovative approach leverages friction-generated heat during the joining process to locally enhance ductility, thereby mitigating the risk of cracking. In this talk, we report our on-going progress of joining of casting Al and 7xxx Al alloys. Crack free joint was achieved based on the process parameters. Lap shear tensile testing was used to evaluate mechanical joint performance and joint interface was characterized by optical, electron microscopes.