Influence of tool pin profiles in the strength enhancement of friction stir welded AA5083 and AA5754 alloys

Abstract

Friction stir welding (FSW) is a well-known technology for joining similar and dissimilar materials. The quality of the weld in FSW is affected by the various process parameters such as tool rotational speed (TRS), tool transverse speed (TTS) and tool pin profiles. This study aims to investigate the effect of three different tool pin profiles on the variation of microstructure and mechanical strength of friction stir welded AA5083 and AA5754 alloys joints. Both of these alloys combinations offer excellent corrosion resistance and formability. As a result, they’re commonly seen in tanks, pressure vessels, shipyards, and trucks. In this work, the FSW methodology focused on varying the TRS of 750, 1000, 1250 and 1500 rpm and TTS as 20, 30, 40 and 50 mm min−1. The surface microstructures of the weldments were analyzed using an optical microscope and scanning electron microscope. Tensile and Microhardness tests were carried out on the weldments to determine the weld strength. Three variety of tool pins, namely straight square, threaded cylinder, and straight cylinder were used for this study. The microstructural and the mechanical properties analysis of the welded samples proved that the straight square tool pin profile is suitable for joining AA5083 and AA5754 alloys. The weldments prepared using a straight square pin profile exhibited good material stream behaviour, uniform spreading of plastic deformation in the weld zone and aided in the reduction of formation of macroscopic defects on the welded zone. Among the process parameters, it was detected that the pin profile displays more impact on tensile strength followed by tool rotation speed and welding speed. According to the findings, the dissimilar weld joint formed at the optimum process parameters had the highest tensile strength of 212 MPa and hardness of 88 HV were: Square Tool Profile, 1250 rpm TRS, and 40 mm min−1 TTS.