Optimizing Friction Stir Welding Parameters for Improved AA6061 and AZ31 Mg Alloy Joints

The purpose of this study is to systematically analyze the impact of various input parameters on the ultimate tensile strength (UTS) of Friction Stir Welding (FSW) joints between magnesium alloys AZ31 and AA6061. We have developed a mathematical regression equation using Response Surface Methodology (RSM) to optimize FSW parameters and enhance the UTS in the welded joints. By utilizing the Central Composite Design approach from RSM, which incorporates feed rate, rotating speed, and tool offset, we are able to streamline the experimental processes and minimize the number of repetitions required. In our experimental setup, a hard metal base sheet (Cu) is placed on the advancing side of FSW, while a soft metal base sheet (Al) is positioned on the retreating side with tool offsets of −1 mm or −1.68 mm. To evaluate internal abnormalities and examine the phase architecture and fracture patterns of the joints, we conducted radiographic and SEM investigations. The highest UTS value ever recorded, 142.69 MPa, was achieved with a tool offset of −1.68 mm, a feed rate of 40 mm/min, and a rotation speed of 1000 rpm. When compared to pure AA6061 alloy, the joint efficiency is 82%. Our updated RSM demonstrates a remarkable 92% accuracy rate, showcasing its reliability and efficiency in maximizing FSW parameters for improved joint strength.