Experimental Study on Ultimate Tensile Strength and Impact Energy of Al-2024 Friction Stir-Welded Joints

This paper focuses on the multi-objective optimization of friction stir welding process parameters. Three input variables, including the axial load (AL), tool rotation speed (RS), and tool tilt angle (TA), were selected to optimize the mechanical characteristics of Al-2024 friction stir-welded (FSW) joints. The ultimate tensile strength (UTS) and impact energy (IE) were selected as output responses to measure the mechanical characteristics of Al-2024 FSW joints. A total of nine experiments, using the L9 orthogonal array as part of the Taguchi method, were performed to determine the significance of the process parameters. Gray relational analysis (GRA) was employed to conduct the multi-objective optimization of these combinations of process parameters. The results of the analysis of variance (ANOVA) showed that the AL has the most significant effect on the UTS and IE of Al-2024 FSW joints, followed by the TA and RS. The Taguchi-based GRA analysis revealed that an AL of 10 KN, a TA of 2 degrees, and an RS of 1500 rpm resulted in an optimal UTS of 333.06 MPa and an IE of 40.62 Joules. In these optimal experimental settings, optical microscopy analysis revealed the presence of a recrystallized fine-grain structure in the heat-affected zone of the welded region.