Influence of Welding Processes on Tensile Properties, Microstructure, and Hardness of Friction Stir Welded AZ31B Magnesium Alloy

Friction Stir Welding (FSW) was performed on 5-mm thick plates, machined from rolled AZ31B Magnesium alloy.The microstructure and defects formation were investigated by optical microscope. The mechanical properties were determined by tensile and hardness tests. Frictional heat and plastic flow during friction stir welding create the fine recrystallized grain (Stir Zone, SZ) and the elongated and recovered grain (Thermo-Mechanical Affected Zone, TMAZ) in the weld zone. Heat affected zone (HAZ), which can be identified only by hardness test due to no difference in grain structure compared with the base metal, is formed beside the weld zone. In this study, the effect of rotational speed on microstructure , hardness and mechanical properties of Friction stir welded Mg AZ31B alloy have been investigated. Friction stir welding (FSW) is carried out at different rotational speeds of 900 rpm, 1120 rpm, 1400 rpm and 1800 rpm with High speed steel (HSS) at a constant welding speed of 40 mm/min, tilt angle of 2.50 and axial force of 5 KN. It is observed that the joint fabricated using HSS tool material at a rotational speed of 1400 rpm obtained higher mechanical properties as compared to those of 900 rpm, 1120 rpm and 1800 rpm