Experimental investigation and process parameter optimization of simultaneous staggered double-sided friction stir welding

With the development of the aerospace industry, the demand for thick aluminum alloy plates used in large aerospace structural components is steadily increasing. However, conventional single-sided friction stir welding (SS-FSW) still encounters significant challenges when welding thick plates. This paper presents a novel simultaneous staggered double-sided friction stir welding (SSDS-FSW) technique, which offers a new approach for joining thick plates. This study conducted welding experiments on 12 mm-thick AA6061-T6 aluminum alloy plates using the SSDS-FSW method. Microstructural observations were performed to investigate the joints' microstructure under various parameter combinations. The macroscopic morphology of the joint cross-section shows that SSDS-FSW enables complete joining of thick plates. The study specifically analyzed the effects of rotational speed, welding speed, and offset distance between the tool pins on the tensile strength and elongation of the joints. Finally, taking tensile strength and elongation as response variables, multi-objective optimization of process parameter was conducted using Taguchi experimental design and grey relational analysis. This optimization aimed to improve the overall mechanical performance of the joints. Optimization result indicated that the joint achieves optimal mechanical properties at a rotational speed of 800 r/min, a welding speed of 150 mm/min, and an offset distance of 4.5 mm between the tool pins on both sides. Experimental verification confirmed that, under this parameter combination, the joint exhibited a tensile strength of 231 MPa and an elongation of 13.55%.