Microstructure and mechanical properties of 2024 aluminum alloy consolidated from rapidly solidified alloy powders

The microstructure and mechanical properties of the rapidly solidified 2024 aluminum alloy consolidated by hot hydrostatic extrusion were experimentally investigated, with special emphasis on finding out the influence of both the two main consolidation parameters, extrusion ratio and temperature, and the solution-aging treatments on the mechanical properties of the alloy. The results show that the optimal extrusion temperature for the consolidation of the alloy powders is 430-450 °C, and that the extrusion ratio should not be less than 21:1. By solution treatment at 495 °C for 1.5 h and subsequent aging at 190 °C for 5 h, peak age hardening occurs for the alloy consolidated by using the above as-optimized processing parameters, with the yield strength σ_s and ultimate tensile strength σ_b of the alloy reaching as high as about 460 and 540 MPa respectively. Meanwhile, the tensile elongation of the peak-aged alloy remains at more than 10%. Transmission electron microscopy observation reveals that the as-consolidated alloy is characterized by a very fine recrystallization structure with submicron-sized grains, and that the grain growth of the consolidated alloy during subsequent solution treatment is quite limited. Peak-aging of the solution-treated alloy gives rise to lots of homogeneously distributed nanometer-sized S' precipitates. The high mechanical strength of the alloy can be attributed to the very fine grain structure and the precipitation of the supersaturated solute elements in the form of homogeneously distributed nanometer-sized S′ precipitates.