| The performance of aluminum alloys has not recently fully met the requirements of aerospace, national defense and civil products. Especially in light of the development requirements of substituting aluminum for steel, the higher mechanical property of aluminum alloys is the urgent need to pursue. Aluminium alloys by powder metallurgy have the double advantages of weight loss and net shaping. However, the important question is that the residual pores in the sintered aluminum alloys will seriously affect the product performance. Powder forging can eliminate the pores of powder metallurgy materials, resulting in making the parts with full density, high performance and complex shape. Aiming at the aluminum alloy products with high performance and complex shape, the powder forging and densification forming technology of the aluminum alloy have been studied by SEM, TEM, XRD, physical thermal simulation, performance tests and so on. Consequently, the theoretical basis and technical support are provided for the application of aluminium alloys by powder metallurgy.The high temperature rheological behavior of the 2A50 aluminum alloy by powder metallurgy was investigated by the isothermal compression experiments in the range of 300-500 ℃ and 0.001-1 s-1 strain rates. On the one hand, the flow stress curves presented as the slow, steadily mounting trend rather than the near steady state. On the other hand, the dynamic recrystallization process was restrained, and grains did not grow up. This was mainly due to the nano-Al2O3 (20-50 nm) with the excellent high temperature stability, which was able to continue to hinder dislocation motion and the grain boundary migration under high temperature, improving the high temperature deformation resistance and restraining the grain growth. The constitutive equation of flow stresses during hot formation was established by the thermal simulation experiment data, and the heavy truck wheel hubs with the good surface quality were successfully produced by the aluminum alloy powder forging. The results showed that under the double action of fine-grain strengthening and dispersion strengthening, the powder metallurgy products had more excellent mechanical properties and stress corrosion resistance compared with the deformation aluminium alloy with the similar components.The sintered billets with 20 mm in diameter prepared by the pure aluminum powder and 2024 aluminum alloy powder were successfully processed into the wires with 1 mm in diameter by rotary swaging. The yield ratio of the prepared wires was closed to 1. Compared with the 1050 industrial pure aluminum, the pure aluminum wire by powder metallurgy had more excellent mechanical properties at both room temperature and high temperature due to the nano-Al2O3 dispersion strengthening. After anealing at 500 ℃, the yield strength and the ultimate tensile strength of the pure aluminum wire prepared by 6 μm powder were close to one time higher than those of the 1050 industrial pure aluminum, and the enlongation of the pure aluminum wire reached 7.2%. The T6 performance of the 2024 aluminum alloy wire by powder metallurgy was very excellent, including the yield strength of 547 MPa, the ultimate tensile strength of 598 MPa and the elongation of 9.1%.The powder liquid forging technology was first put forward, and the 2A50 aluminum alloy and the h-BN/Al composite with full density and high performance were successfully fabricated by this technology. When the liquid volume fraction in the 2A50 aluminum alloy was 100%, the grain growth would not occur due to the nano-Al2O3 hindering the grain boundary migration. The relative density of the h-BN/Al composite reached up to more than 99% of the theoretical density, and a sharp interface between the h-BN and the aluminum matrix was observed. Furthermore, the h-BN/Al composite prepared by 2 μm aluminum powder showed the optimal comprehensive mechanical properties of hardness, compressive strength and fracture strain. |
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