Characterization of microstructure, mechanical properties and formability for thermomechanical treatment of friction stir welded 2024-O alloys

Abstract

The microstructure, mechanical properties, and formability of friction stir welded (FSW) Al alloys after thermomechanical treatment are investigated using detailed microstructural characterization and numerical simulation. FSW joints prepared using a high heat input (rotation rate: 800 rpm; welding speed: 100 mm/min) show uniform grain-size distribution, consequently exhibiting better thermal stability during solution treatment at 450–495 °C. Abnormal grain growth is not observed in the joint due to an increase in the Zener pinning value. Further, the solution-treated joints exhibit exceptional formability, with a maximum bulging height ~1.5 times that of the as-welded joints. The tensile strength of the joints is equal to that of the base metal (424 MPa) due to the proliferation of dislocation, refinement and increase of precipitates in the weld induced by plastic deformation during the forming process.