Experimental Investigation of Mechanical Properties in Friction Stir Welding for Butt Joints with Different Thicknesses Using Response Surface Methodology

The growing demand for prefabricated tailor-welded blanks in aircraft panel manufacturing stems from their ability to streamline assembly, reduce material usage, save time, and cut costs. Friction stir welding, known for overcoming common defects in conventional methods, is explored in this study. Similar materials with varying thicknesses are welded, evaluating performance with surface response methodology. Central composite design of experiments, with tool rotation speed and welding speed as factors, yields tensile strength, percentage elongation, and hardness as output responses. ANOVA confirms experimental design adequacy, and mathematical models reveal response surface trends. Microstructural analysis investigates material deposition in varying thickness workpieces. Tensile strength response surfaces show significant variations, with the peak of 149 MPa achieved at 900 rpm and 80 mm/min, approximately 80% of the base metal's strength. The highest and lowest tensile strength weld joints exhibit average grain sizes of 7.78 and 13.6 µm, respectively.