Influence of electrode configuration and rivet dimensions on joint formation and performance in resistance riveting welding of AA6061/AZ31 to DP590 sheets

Resistance riveting welding (RRW), as a metallurgical-mechanical hybrid joining technique for dissimilar materials, enables multi-material assemblies. However, the effects of electrode configuration and rivet geometry on welding processes and joint quality remain insufficiently understood. This study systematically investigates the optimization of electrode arrangements and rivet dimensions in RRW processes for joining 6061 Al alloy/AZ31 Mg alloy to DP590 steel, respectively. The electrodes used in the RRW process are two types of flat electrodes: one is a 6.6 mm diameter flat electrode truncated from a tapered electrode (T-type), and the other is a 4 mm diameter flat electrode truncated from a spherical electrode (S-type). This study developed an efficient quarter-symmetry three-dimensional finite element model validated through experimental welding trials to ensure accuracy and reliability. Numerical simulations evaluating three electrode configurations (T-T, T-S, S-S) revealed that the T-S configuration achieved the largest nugget diameter while minimizing the heat-affected zone (HAZ) in the Mg alloy sheet, making it ideal for RRW. Furthermore, investigations into rivet dimensions revealed that cone angle, shank diameter, and height significantly affect the forming process and mechanical performance. Optimized dimensions were determined to be a cone angle of 120°, a shank diameter of 5 mm, with shank heights of 1.1 mm for Al alloys and 1.25 mm for Mg alloys. Implementing these optimized rivets enhanced the mechanical performance, with the peak load of Al-steel joints increasing from 5.22 kN to 6.35 kN, and the peak load of Mg-steel joints improving from 4.31 kN to 5.47 kN.