Research On Preparation And Properties Of SICP/2024AL Composites

For the purpose of accurate optical in Aerospace space engineering structure applications, SiCp/2024Al composites were fabricated by vacuum hot pressing plus sintering. The density is the evaluations for light indicator. The coefficient of thermal expansion is the evaluations for dimensional stability. Tensile strength and hardness is the evaluations for mechanical property. By using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction, dilatometer, tensile test, and Brinell hardness, on the effects of different preparation process the microstructure and the mechanisms of its evolution were studied for determine the optimal preparation technology. Influence of heat treatment on the microstructure of SiCp/2024Al composites prepared by vacuum hot pressing plus sintering were studied, its strengthening mechanism were discussed. In addition, the dynamic compressive properties of SiCp/2024Al composites were explored.The result showed that adding SiC particles into the matrix2024Al matrix improved the mechanical properties of the composite, which played a very good strengthening effect, but also greatly reduced the material coefficient of thermal expansion. The best preparation for the sintering temperature is580℃, SiC particle size of3.5μm, which microstructure were more compact, interface bonding were in good condition. There are a lot of Al2Cu phase in matrix. The tensile properties of composites using best preparation could reach283MPa. The thermal expansion coefficient of composites was12.32×l0-6K-1.SiCp/2024Al composites prepared by vacuum hot pressing sintering heat treatment process were solution treated at490℃for1h, then at170℃aging10h. After heat treatment, the hardness and tensile strength of SiCp/2024Al composites had greatly improved, tensile strength reached409MPa. The relative density of the composites was97.3%. The thermal expansion coefficient of the composites was13.12×l0-6K-1. Microstructure of SiC particles and the matrix interfacial dislocation density in the matrix alloy increase, mainly for the second phase of needle bar of Al2CuMg phase and a small amount of Al2Cu phase. When the composite material in the plastic deformation process, a large number of dislocations in matrix interaction Al2CuMg phase, forming a pinprick, hinder the dislocation line motion so as to increase the material deformation resistance, achieve the precipitation strengthening effect, thus improving the mechanical properties of the whole material.The compressive mechanical properties of SiCp/2024Al composites were investigated under high strain rate by using Split Hopkinson Pressure Bar (SHPB) and stress-strain curves under various strain rates were obtained. The results showed that there did not exist macroscopic damage of shear failure and crack. The composites had suffered different degrees of drum deformation. Materials exhibit good plastic toughness. Different strain rates did not affect much on flow stress and stress-strain curve trend of SiCp/2024Al composites, which performance as rate insensitive materials. At the same volume fraction, the impact of the same load, different particle sizes have a significant impact on the dynamic compression of SiCp/2024Al composites. With decreasing particle size, geometry compression deformation in the necessary dislocation density is high, the better the reinforcement effect, the ability to bear the load of more strong, yield value and flow stress increases stress.