Influence of tool pin geometry on metallurgical and mechanical properties: Friction stir welded dissimilar AA 2014-T6 and AA 5052-H32 alloy plates

Friction stir welding (FSW) is a widely utilized solid-state joining process, known for producing high-quality welds, particularly in aluminum alloys in aerospace, locomotive, automotive, and marine applications. This study investigates the effect of various Tool pin geometries on the mechanical properties of AA2014-T6 (Al-Cu) and AA5052-H32 (Al-Mg) aluminum-welded plates. Tool pin geometries, such as cylindrical, taper-threaded, and square pin profiles, have a significant impact on the weld quality, tensile strength, hardness, and microstructural characteristics of the welded joints. The research emphasizes optimizing these pin geometries to enhance weld integrity and achieve superior mechanical performance in welded aluminum alloys. The microstructure of the weld zone (WZ), thermomechanically-affected zone (TMAZ), and heat-affected zone (HAZ) in the welded samples was analysed, using Scanning Electron Microscopy (SEM) and an optical microscope. Energy Dispersive X-ray Spectroscopy (EDS) was employed to determine the elemental composition of the weld zone. Visual examination confirmed the absence of surface defects, such as voids, surface cracks, and higher flash, of the welded joints. Thus, dissimilar aluminum alloys formed weld zones, characterized by an equiaxed and fine-grained structure. The weld joint's tensile strength reached 94.66% of the base metal strength of AA5052-H32 and 44.51% of the base metal strength of AA2014-T6. The peak UTS of 213 ± 1 MPa indicates an efficient weld joint, achieving 94.66% of the weaker base material's strength, with a square pin tool. The highest 127.15 HV and lowest 106.69 HV average hardness were achieved using a square pin tool and a cylindrical pin tool, respectively.