Comparative analysis of macrostructure and tensile behavior in 90° and 45° corner-butt Al–Mg–Si joints fabricated by friction stir welding

Friction Stir Welding (FSW) is influenced by probe design, pin geometry, and joint configurations. Among various FSW joint types, corner-butt-joints remain one of the most challenging configurations due to their restricted material flow. Consequently, their mechanical performance tends to be lower than that of conventional butt joints, while systematic investigations on parameter variations remain relatively limited. This study aims to evaluate the combined influence of spindle speed, traverse speed, and axial pressure on the thermal, microstructural, and mechanical behavior of Al–Mg–Si corner-butt joints produced by FSW, with emphasis on process parameter effects on tensile strength and fracture morphology. Two corner joint variations were examined, which are corner-butt and corner-butt 45°. Process parameters varied within spindle speeds, traverse speeds, and axial pressures. K-type thermocouples recorded transient temperatures, while microstructure, hardness, and tensile tests characterized the joints’ performance. The highest tensile stress, 140.7 MPa, was achieved in the corner-butt joint at a feed rate of 10 mm/min and spindle speed of 1000 rpm. The lowest tensile stress, 50.5 MPa, occurred at a 30 mm/min and 2000 rpm under the same axial pressure. It is accompanied by the fracture morphology as shown by the microstructure results. Proper coordination of spindle speed, traverse speed, and axial pressure effectively minimizes flash and enhances mechanical integrity. The corner-butt (90°) configuration outperforms the 45° design, confirming that tool control and geometric confinement are critical for achieving defect-free, high-strength joints in FSW applications.