Impact of tool geometry and friction stir welding parameters on AZ31 magnesium alloy weldment wear behaviour and process optimization

This study investigates the impact of friction-stir welding (FSW) tool pin shape (TPS) and processing variables, viz., rotation speed (RS), axial load (AL), and traverse speed (TS), on weld beads' wear characteristics as per ASTM G99 standard. Wear rate (WR), friction force (FF), and coefficient of friction (CoF) are analyzed based on Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). FSW performed with a hexagonal TPS provides a better material flow between the plates, influencing the joint's strength and improving the wear resistance of weldments. Higher RS leads to high material flashing, providing lower strength and wear properties. Changes in TPS from triangle to pentagon and from pentagon to hexagon produced higher tensile strength, at 11.16% and 12.15%, respectively. The Chimp Optimization Algorithm (ChOA) shows an optimal condition of hexagon TPS, AL of 2 kN, RS of 1800 rpm, and TS of 25 mm/min, whereas TOPSIS optimal condition are hexagon TPS, AL of 4 kN, RS of 1400 rpm, and TS of 50 mm/min. Confirmation experiments with optimal conditions shows, ChOA producing lower WR, CoF, and FF by 12.5, 2.56, and 1.54% than TOPSIS. Compared with TOPSIS, ChOA produced lower WR, CoF, and FF by 12.5%, 2.56%, and 1.54%.