Influence of Tool Pin Profiles on Friction Stir Welding of Copper

Abstract

The influence of tool pin profiles on microstructure and mechanical properties of friction stir welded copper was studied. The different tool pin profiles such as taper cylindrical, taper cylindrical with threaded, triangular, square, pentagonal, and hexagonal having constant shoulder diameters were used to fabricate the joints. Tool rotational speed and traverse speeds were fixed at 900 rpm and 40 mm/min, respectively. The experimental results revealed that the sound defect free joints could be obtained by using six different tool pin profiles and the fracture locations were outside the weld zone on the retreating side. From the investigation it was found that the joints made by using square tool pin profile resulted in better mechanical properties compared to other tool pin profiles which is due to more pulsating actions and with 1.56 dynamic to static volume ratio. The tensile properties of all weld joints showed a relative correspondence to the variation of the hardness in the weld zone. The joint efficiency of square pin profile is more (85%) of the base metal compared to other pin profiles. The observed results were correlated with the microstructure and fracture features.