Abstract In the present study, similar Aluminum (AA3003) alloy pipes with a thickness of 5 mm were friction stir welded using a high-speed steel (HSS) tool with a cylindrical pin profile. Welding was done at three different rotational speeds and three traverse speeds corresponding to pipes of three different diameters. Six combinations of rotational speed and traverse speed were used to observe the effect of energy input on the properties, specifically tensile strength and microhardness, as well as grain size of the resulting microstructure. This systematic variation in welding parameters was designed to assess how changes in energy input influence both the mechanical performance and microstructural attributes of the welded joints. The tensile test results indicated that an ultimate tensile strength (UTS) of 84% relative to the base metal was achieved at a rotational speed of 900 rotations per minute(rpm) and a traverse speed of 131.94 mm/min. The impact energy corresponding to these parameters was found to be 38% more than base metal which is a remarkable contribution. This combination of welding parameters facilitated optimal material flow and bonding, resulting in improved tensile properties of the welded joint. Additionally, the tensile results showed a consistent pattern in the tensile failure of the welded samples, where the joint failure occurred at the location with the lowest hardness in the welded region. This correlation highlights the critical influence of hardness distribution on the structural integrity of the welds, indicating that areas with reduced hardness are more prone to failure under tensile loading of FSWed joints.
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