Friction Stir Welding of Copper and its Alloys Using Different Tool Pin Profiles

Friction Stir Welding (FSW) is relatively new joining process that is presently attracting considerable interest. The process is solid-state in nature. Copper and Brass are widely used engineering materials in electrical and chemical industry because of their high electrical and thermal conductivity, high corrosion resistance and high strength. The main objective of this work is to investigate the feasibility of Friction Stir Welding (FSW) of copper and brass. FSW trials were carried out on 6 mm thick commercially pure copper and brass plates with travel speeds ranging from 30 to 75 mm/min and tool rotational speeds ranging from 1300 to 1600 rpm. The FSW tool pin was made of high speed steel (M2) hardened and tempered to 55 HRC. Friction stir tool is the key art of friction stir welding processes. The tool pin profile used in this study are straight cylindrical, taper cylindrical, threaded cylindrical and tapered threaded cylindrical with a pin lengths of 5.0 mm to 5.4 mm. Defect free welds were obtained using several sets of parameters. Vickers micro hardness testing and tensile tests were carried out to evaluate the mechanical properties of sound welds. Use of tapered threaded tool and tool rotational speed of 1300 to 1600 rpm resulted in high quality welds with good mechanical properties. Different microstructure zones were revealed by optical microscopy (OM). The Weld Zone (WZ) and Thermo Mechanically Affected Zone (TMAZ). The WZ fine equiaxed grains were observed and TMAZ fine elongated grains were observed.