Microstructural stability and strength correlation in AGG-affected friction stir welded AA2024-T4 joints

The high-strength AA2024 aluminium alloy was friction stir welded using optimised parameters of tool rotational speed of 500 rpm, welding speed of 100 mm/min and tilt angle of 1.5 deg. Thermo-mechanically heat-affected zone typically weakens due to precipitate dissolution and coarsening. Post-weld heat treatment, involving solution treatment and artificial ageing, was applied to improve joint strength. The treated joint exhibited higher strength (411 MPa) than the as-welded condition due to grain refinement, uniform precipitate distribution, and abnormal grain growth. Enhanced mechanical properties resulted from stable grain structures in the stir zone.