Welding parameters influence on fatigue life and microstructure in resistance spot welding of 6061-T6 aluminum alloy

The fatigue behavior of resistance spot welding (RSW) in aluminum 6061-T6 alloy (AlMg1SiCu per International Standard Office nomenclature) was experimentally investigated. Three welding conditions, denoted as “nominal”, “low” and “high”, were studied to determine the microstructure of the weld nuggets. The process optimization included consideration of the forces, currents and times for main weld and post-heating. By successive iterations and “witness samples” collected, the optimum welding parameters were determined. Load control cyclic tests were then conducted on single weld lap-shear joint coupons to study the microstructure and fatigue life properties. These tests were used to characterize the fatigue behavior in spot welded specimens to elucidate the influence of the process parameters. This work revealed that the welding process parameters have a great influence in the microstructure and fatigue life of the 2 mm-thick aluminum sheet resistance spot welded joints. Different fatigue failure modes were observed at several load ranges and ratios for a constant frequency and three welding currents.