Effect of tool rotation and welding speed on microstructural and mechanical properties of dissimilar AA6061-T6 and AA5083-H12 joint in friction stir welding

The study investigates joining AA6061-T6 and AA5083-H12 aluminum alloys, each 6 mm thick, in a butt joint. It aims to analyze the impact of varying input parameters on the microstructural and mechanical properties of the joints. Three tool rotation speeds (900, 1,120, 1,400 rpm) and welding speeds (40, 63, 80 mm min-1) are examined. Temperature in the weld zone correlates with tool rotation speed positively and welding speed inversely. Initially, the average grain size in the stir zone decreases with increasing tool rotation (900-1,120 rpm) and welding speed (40-63 mm min-1), then increases with further increments (1,400 rpm, 80 mm min-1). Tensile strength increases by 7 % from 900 to 1,120 rpm but decreases by 19 % at 1,400 rpm. Similarly, it rises by 14 % from 40 to 63 mm min-1, then decreases by 6 % at 80 mm min-1. Optimal mechanical properties occur at 1,120 rpm and 63 mm min-1, with ductile mode failure identified in joints with higher efficiency.