An experimental investigation on friction stir welding of AZ31B magnesium alloy

The conventional fusion welding of magnesium alloys often produces porosity in the weld joint, which deteriorates its mechanical properties. To solve this problem, friction stir welding (FSW), a solid-state welding technique, can be applied for joining of magnesium alloys. In this investigation, an attempt was made to understand the effect of FSW process parameters such as tool rotational speed, welding speed, and axial force on tensile properties of AZ31B magnesium alloy. Fourteen joints were fabricated using different levels of tool rotational speed, welding speed, and axial force. Tensile properties of the welded joints were evaluated and correlated with the weld zone microstructure and hardness. From this investigation, it is found that the joints fabricated using a tool rotational speed of 1,600 rpm, a welding speed of 0.67 mm/s, and an axial force of 3 kN yielded superior tensile properties compared to other joints. Optimum level of heat generation, formation of finer grains, and higher hardness are the main reasons for the superior tensile properties of these joints. Fatigue properties of FSW joints were evaluated, and it was found that fatigue properties of FSW joints were slightly lower than the base metal.