Sustainability of friction stir welded AA6082 plates through post-weld solution heat treatment

Abstract

Abstract There is high demand for a novel fabrication technique that requires low energy consumption rate for its operation, environment-friendly and sustainable. The aforementioned attributes make friction stir welding (FSW) to be globally accepted in joining aerospace alloys that are difficult to weld using the conventional arc welding technique. In this investigation, friction stir welds were processed plastically and characterized thermo-mechanically. Also, three welding speeds i.e. 90 mm/min, 120 mm/min and 150 mm/min were adopted using tool-rotational speed 950 rpm and 1150 rpm respectively. An attempt was made to investigate the effect of severe plastic deformation and solution heat treatment on the tensile property of the welds. A solution heat treatment temperature of 4700C for 30minutes, held for 30 another minutes and water quench. The mechanical properties of the welded joints after solutionizing was linked to the sustainability of FSW process. A maximum tensile strength (UTS) of 100 MPa for the as-weld specimen and 233.5 MPa after post-weld heat treatment were recorded at welding parameter 150mm/min and 950 rpm respectively. Meanwhile, the higher the weld-pitch (mm/rev) and the heat input (J), the softer the weld joints and the lower the UTS. Aside from point of fracture which were observed to be at the thermo-mechanical zone (TMAZ), the disparities in composition evolution and physical features of all the welded joints were similar. In conclusion, solution heat treatment improved the weld strength as well as the ductility. The improved value of UTS through solution heat treatment makes the weld joints reliable and FSW a sustainable process.