Microstructure and Mechanical Properties of Friction Stir Welded Joints of Dissimilar AA6061-T6 and AA7075-T6 Aluminium Alloys

Dissimilar friction stir welding was carried out between AA6061-T6 and AA7075-T6 aluminum alloys. The effect of tool rotational speed and welding speed, on microstructure and mechanical properties were analysed in detail and presented. The tool rotational speed, welding speed, axial load and shoulder diameter to pin diameter (D/d ratio) were the parameters taken into consideration for the study. It was concluded that the tensile strength and hardness value gradually increased with the increase in tool rotational speed and decreased with the further increase in tool rotational speed. The microstructural analysis was carried out for the high strength specimen at various zones. Fine grain size and proper material mixing were observed in the stir zone. Fractographic image of the fractured surface for the high strength joint was presented and discussed. The joint fabricated with tool rotational speed 1000 RPM, welding speed 25 mm/min, axial load 6 kN and D/d ratio 3 exhibited superior mechanical properties when compared to all other joints.