Effect of welding conditions on the mechanical and microstructural behavior of AZ31B magnesium alloy welded joints by the FSW process

Magnesium alloys have experienced continuous growth in industrial applications by ensuring a good in strength-to-weight ratio. nevertheless, these alloys have limitations when welded by conventional processes, culminating in degradation of mechanical properties. Friction stir welding, which is more efficient as it operates below the melting temperature range, was used in this study to evaluate the influence of welding parameters on the mechanical properties of AZ31B Mg alloy welded joints. Uniaxial tensile and microhardness tests were performed, along with analyses using an optical microscope and a scanning electron microscope. Significant mechanical strength was achieved, with average values ranging from 155 to 197 MPa, resulting in an efficiency of 57% to 72%. The statistical analysis demonstrated that the effects were statistically significant within the experimental range, particularly with respect to the tool tilt angle. The fractures were concentrated on the interface between the base material and the joint mixing region. Significant grain refinement was achieved through the combined effects of temperature, mechanical work, and plastic flow, resulting in an average grain size reduction of approximately 68% relative to the base material and microhardness values of about 66 HV.