Development of friction stir welding technique at right angle (RAFSW) applied on butt joint of AA6061-T6 aluminum alloy

Friction stir welding (FSW) is a solid-state joining process, which has prominent advantages over common fusion welding methods like MIG welding. However, equipment costs and royalties act as the main barriers to the widespread use of this technique in today's industry. Thus, developing low-cost FSW techniques could pave the way for potential industrial users. In this research, we are going to characterize and optimize a recently developed FSW technique at right angle (RAFSW) using low-cost three-axis CNC machine tools. To this end, a full study was done to gain a deep insight through the effect of RAFSW process parameters on generated axial forces and tensile properties of AA6061-T6 butt-welded flat bars of 6.35 mm thick. Experiment planning and modeling of the results used Taguchi design of experiments method and artificial neural network modeling respectively. From these models, an efficient working window of process parameters has been established so that CNC machines with minimized capacity and stiffness can produce high-quality welds repeatedly. After natural aging, the ultimate tensile strength reached a maximum of 253 MPa and stays above 247 MPa within the working window. Moreover, the robustness of the technique and the effect of artificial aging on the strongest samples have been evaluated. We found that the ultimate tensile strength of artificially aged samples attained 300 MPa. Finally, microstructure images and micro-hardness measurements of the strongest welded samples complete the analysis. The outcomes of this research have a great impact on making the recently proposed RAFSW technique reliable for industrial users.