Influence of Tool Probe Profiles on the Microstructure and Mechanical Properties of Underwater Friction Stir Welded AA5083 Material

Friction stir welding (FSW) is a non-traditional welding technique used to join similar and dissimilar materials that are difficult to join using fusion techniques. Furthermore, when compared to traditional welding, this type of welding is more energy-efficient and environmentally friendly. Tool probes have a significant impact on the mechanical and microstructural properties of metallic joints in FSW. In this work, different probe profiles such as straight cylindrical, straight threaded, and straight hexagon (SH) are used to join the AA5083 aluminum alloy plates. Mechanical and microstructural characterization of welded plates is performed using various probe profiles. When the plates are welded using a straight hexagonal (SH) probe profile and process parameters such as tool rotational speed of 1200 rpm, tool transverse speed of 40 mm/min, and tool tilt angle of 1°, mechanical properties such as ultimate tensile strength, yield strength, percentage of elongation (EI %), and hardness are significantly improved. The electron backscatter diffraction analysis was carried out to know about the microstructural changes that are the cause of the mechanical property alteration. Analysis reveals that the nugget zone (NZ) exhibits recrystallized fine grains with an equiaxed structure as a result of dynamic recrystallization (DRX). In NZ, a high proportion of high angle grain boundaries are found, resulting in improved mechanical properties of the joint.