Comparison of the Resistance Spot Weldability of AA5754 and AA6022 Aluminum to Steels

In this paper, a traditional resistance spot welding (RSW) process in combination with a GM-patented Multi-Ring Domed (MRD) electrode was used to join two types of aluminum alloys, AA5754-0 and AA6022-T4, to interstitial-free low carbon steel (LCS). Parallel studies were carried out for AA5754-LCS and AA6022-LCS resistance spot welds to investigate the effects of aluminum contact resistance on the weld profile, interfacial microstructure, defect distribution, and coach peel performance. The results indicated AA5754-0 develops a higher contact resistance when exposed to atmospheric conditions. This resulted in a degradation of the RSW process due to increased internal expulsion of the molten aluminum nugget and concurrent reduction in aluminum nugget size that contributed to a loss in joint mechanical performance. By contrast AA6022-T4 exhibited a lower contact resistance, which minimized internal expulsion and promoted the retention of larger aluminum nuggets. The larger AA6022 weld nuggets exhibited improved mechanical performance in comparison to the smaller 5754 nuggets.