Influence of tool rotation speed on microstructural characteristics and mechanical properties of friction stir welded AA2014-T6 aluminium alloy

Friction stir welding (FSW) is a promising solid-state welding process for precipitation hardening and high strength aluminium alloys. An experimental and theoretical investigation was carried out to check the significance of tool rotation speed on microstructural characteristics and tensile properties of high-strength alloy AA2014. FSW joints were made with varying tool rotation speed from 1,100 rpm to 1,900 rpm with an equal increment of 200 rpm, while the other parameters such as welding speed, shoulder diameter and tool tilt angle were kept constant. The strength of FSW joints was correlated with microhardness, microstructure and fractographs. The joint fabricated with the tool rotation speed of 1,500 rpm, welding speed of 50 mm/min, shoulder diameter of 6 mm and tool tilt angle of 1.5° exhibited superior strength (376 MPa) than the other joints. It could be achieved by the balanced flow of material and defect-free in the stir zone.