An investigation on microstructure and mechanical properties of post-weld heat-treated friction stir welds in aluminum alloy 2024-W

The present work describes the results obtained from microstructural and mechanical evaluation of post-weld heat treated friction stir welds of 2024 aluminum alloys in the W temper state. Post-weld heat treatments have been carried out at 510 degrees C for 2.5 h followed by ageing at room temperature for 6 months, at 100 degrees C and 190 degrees C for 10 h, and by cooling in static air (O-temper). The solution treatment caused abnormal coarsening of the grains in the stir zone, which resulted in a drop in microhardness. The strength of the as-welded joint was significantly incrased by post weld heat treatments. The maximum hardness and strength values were obtained in T6 (190 degrees C, 10 h) treated joint. However, the T6 (190 degrees C, 10 h) treated joint had the lowest ductility. On the other hand, the tensile properties of the post-weld heat treated joints were far lower than those of the unwelded base materials in the same temper states. In addition, the post-weld heat treatments did not significantly change the fracture locations of the friction stir welds