Effect of Threaded Pin Tool for Friction Stir Welding of AA6061-T6 at Varying Traverse Speeds: Torque and Force Analysis

Abstract

Friction stir welding (FSW) of 6-mm-thick AA 6061-T6 plates for taper threaded tool were studied in this investigation in terms of torque and different forces. A plain taper tool in addition to threaded tool is also incorporated in the study to analyze the effectiveness of threads. Welding was conducted at a constant rotational speed of 1100 RPM and varying traverse speeds between 45 and 135 mm/min. The distribution of torque, Z-force and X-force generated during the FSW process discloses a substantial knowledge about the weld formation. The torque and forces increase with the increase in traverse speed for both the tools where higher values were attained by taper threaded tool. The macrostructure reveals a sudden increase in thickness of shoulder induced region and nugget area, followed by a gradual decrease for both of the tools with traverse speed. Comparatively larger shoulder induced region and weld nugget are obtained for taper threaded tool. The maximum values of these entities were attained at 75 mm/min for taper threaded tool, and a difference of 0.13 mm and 7.52 mm2, respectively, was obtained with taper tool. Finer grains with an average diameter of 5.82 µm are obtained for taper threaded tool and 8.68 µm for taper tool. Maximum tensile strength was obtained for taper threaded tool with a joint efficiency of 70.96% and 60.32% for taper tool. A mixed mode of failure is observed at a higher traverse speed for taper tool, whereas all welds for taper threaded tool exhibit ductile fracture.