Effect of tool rotational speed on friction stir welded AA6061-T6 scarf joint configuration

The present research introduces comparatively new scarf joint configuration (SJC) method for friction stir welding (FSW) of AA 6061-T6 plates and explores the impact of different tool rotation speeds (TRS: 500 rpm to 1400 rpm) at constant tool traverse speed (TTS) of 2 mm/s and tool tilt angle (TTA) of 2° on scarf joint weld quality. Scarf joint configuration, a recently introduced joint configuration, was considered with scarf angles 60° for this study. Analyses on force and spindle torque (Sp.Torque), macrostructure, microstructure, and mechanical property are compared at different TRS. The study found that as the TRS increases, the amount of X-force (longitudinal force), Z-force (vertical force), and Sp.Torque produced through welding decreases. For all parameters, sound- and defect-free joints were obtained. Fine recrystallized grains are generated in NZ for all of the parameters. It has been observed that maximum hardness of 78.62 HV 0.1 was obtained in the centre of nugget zone (NZ) at TRS of 1100 rpm. Similarly, maximum ultimate tensile strength (UTS) of 267 MPa with joint efficiency of 86% was obtained at a TRS of 1100 rpm. This unique scarf joint feature may provide a boost to potential joint strength enhancement techniques while lowering production costs. Graphic Abstract