Joining Magnesium Die Casting using Self-Piercing Riveting with a Rivet Receiver

As automotive companies increasingly incorporate lightweight materials into the new vehicles to improve fuel economy, development of joining technologies for different material combinations is also required. As a key mechanical fastening technology for dissimilar materials, self-piercing riveting (SPR) has been well established in joining aluminum and steel. However, the application of SPR on magnesium alloys was impeded mainly by the cracking issue resulting from its limited slip-systems at room temperature when magnesium was restricted to be on the bottom due to galvanic corrosion concern. To solve this issue without much modification on existing process, a concept of adding a layer of ductile material underneath of the bottom magnesium to receive the rivet is proposed. An experiment was designed to investigate this concept by joining a mild steel and a magnesium die casting with a ductile aluminum as a rivet receiver. Comparison was made on button surface quality, cross-section characteristics and mechanical performance at 3 different configurations (no rivet receiver, a thinner river receiver and a thicker river receiver). A robust crack-free joint of CR3 mild steel and AM60B magnesium high pressure die casting was achieved by adding a rivet receiver made of 5052H32 aluminum.