Friction stir lap welding of AA 2139 and AA 7075: Processing and sustainability analysis

Friction Stir Welding (FSW) is increasingly adopted by industry to join difficult-to-weld materials thanks to its high energy efficiency and environmental sustainability. However, despite the extensive research, the studies on the sustainability of the process in correlation with the mechanical performance of the joints are still in the early stages. This study combines the analysis of energy consumption and mechanical properties in the FSW of dissimilar aluminum alloys, exploring different combinations of key process parameters. A gate-to-gate Life Cycle Assessment (LCA) was conducted to evaluate the environmental impact of the FSW process. From a sustainability standpoint, the optimal result was achieved using the highest travel speed (TS) of 270 mm/min in combination with a tool rotational speed (TRS) of 2000 rpm. Under these process conditions, reductions of up to 61 % in global warming potential (GWP), 62 % in total energy consumption, and 62 % in specific welding energy (SWE) were observed at the cost of approximately a 13 % reduction in flexural strength. As a result, power/energy, microhardness, microstructure, and flexural tests were incorporated into welding parameter maps to help in identifying minimum energy consumption and GWP points within the process constraints needed for maintaining good welding quality.