Influence of Joint Angle on Residual Stress, Microstructural Evolution, and Mechanical Performance of Friction Stir Welded AA۶۰۶۱ Aluminum Alloy Using a Novel Adjustable Angled-Joint Fixture

Friction stir welding (FSW) is a solid-state joining technique capable of producing high-quality joints through frictional heating and severe plastic deformation below the melting point. In this study, the effect of joint angle on the residual stress evolution and integrated mechanical response of AA۶۰۶۱ aluminum alloy was experimentally investigated. Rolled plates (۱۸۵ × ۱۰۰ × ۴ mm) were annealed prior to welding to improve ductility and material flow. A novel adjustable fixture enabled the fabrication of joints at ۹۰°, ۱۵۰°, ۱۶۵°, and ۱۸۰°, while welding was performed at ۱۴۰۰ rpm and ۱۶ mm/min using angle-specific tools. Residual stresses were quantified using a hybrid digital image correlation–incremental hole drilling (DIC–IHD) method. Microstructural characterization and through-thickness microhardness measurements were conducted to elucidate thermo-mechanical behavior, and tensile tests were performed to evaluate joint performance. Increasing the joint angle progressively reduced tensile residual stresses from ۱۸۹.۵ and ۱۷۷.۳ MPa at ۹۰° to ۱۵۹.۳ and ۱۵۰.۳ MPa at ۱۸۰° in longitudinal and transverse directions, respectively. The ۱۶۵° configuration exhibited the most homogeneous microstructure, uniform hardness distribution, and superior tensile strength. The results demonstrate that joint angle governs material flow symmetry and recrystallization behavior, leading to an optimal thermo-mechanical condition at ۱۶۵° for enhanced structural performance.

کلیدواژه ها:

Friction Stir Welding ، Joint angle ، Mechanical properties ، Digital image correlation ، Microstructural evolution