Influence of tool pin profile on the microstructure and mechanical properties of friction stir welded copper/brass dissimilar joints

Special applications such as valves, pumps, condensers, precision engineering, and biomedical components frequently demand the use of copper and its alloys due to their desirable properties. Copper is inherently soft, while brass offers excellent corrosion resistance. This study investigates the influence of four different tool pin profiles namely, straight cylindrical, plain taper, triangular, and taper threaded on the formation and properties of dissimilar copper–brass joints produced by friction stir welding. The welding parameters were optimized at a tool rotational speed of 750 rpm, traverse speed of 75 mm/min, and tool tilt angle of 2.5°, with the aim of enhancing mechanical properties. The findings reveal that joints produced using the taper-threaded tool pin profile exhibit superior mechanical performance compared to other profiles. The maximum tensile strength of the weld produced by taper-threaded pin is 360 MPa. Microstructural analysis of the stir zone confirms the presence of fine, recrystallized grains in welds made with the taper-threaded tool. This enhanced performance is attributed to the pulsating action characteristic of the taper-threaded pin. Further, it may be attributed to the formation of intermetallic compound as CuZn, Cu 5 Zn 8 , and CuZn 3 in the weld region at optimum level.