Exploring the Impact of Friction Stir Welding Parameters on Mechanical Performance and Microstructure of AZ91C Magnesium Alloy Joints Using Taguchi Method

In this study, we investigated the influence of process parameters on the mechanical properties of AZ91C magnesium alloy joints produced by friction stir welding (FSW). A Taguchi L9 orthogonal array was employed to design the experimental matrix, and the input variables were analyzed. Tensile strength and hardness values were measured for different input parameters, and their interactions were assessed through interaction plots for ultimate tensile strength (UTS) and Vickers hardness (HV). The signal-to-noise (S/N) ratios were calculated, and S/N ratio plots were generated to further understand the effects of the input parameters on the mechanical properties. Microstructural evaluations were carried out on the base metal and stir zone (SZ) of the specimens produced under various process conditions. Additionally, the appearances of the FSW samples with the minimum and maximum tensile strengths were compared. The results revealed complex relationships between the process parameters and mechanical properties, with both main effects and interactions playing significant roles in determining the performance of the FSW joints. Notably, an optimal combination of process parameters (tool rotation speed of 1250 rpm, welding speed of 40 mm/min, and plunge depth of 0.3 mm) resulted in the highest ultimate tensile strength (UTS) and hardness (HV) values. Microstructural analysis showed that FSW significantly refined the grain size, contributing to the improvement of mechanical properties.