Effect Of Heat Treatment On The SiC_p/2024 Al Composites Of Powder Semi-solid Thixoextruding Forming

Although silicon carbide aluminum matrix composites was only developed several decades, it is widely used for modern aspects of our life, from electronic packaging substrate to aircraft parts. The SiC_p/2024 Al composite material with excellent performance has already been successfully used in the field of silicon carbide aluminum matrix composites. In this paper, the SiC_p/2024-aluminum-matrix-composites’ bars were prepared by the method of powder semi-solid thixoextruding forming. The powder semi-solid thixoextruding forming brings together the advantages of powder metallurgy, semi-solid processing and extrusion technology. This way can make composite material get the distribution of SiC uniform, less segregation, better interfacial adhesion, low porosity and so on. Through EPMA, XRD and SEM, we can qualitatively and quantitatively analyse composite of structure and components,and test the composite hardness, tensile strength and elongation etc. We research the binding interface between SiC particles and 2024 matrix, SiC particles in the matrix distribution and emphatically discusses the solution time and solution temperature, aging time and aging temperature which influence the microstructure and mechanical properties of SiC_p / 2024Al-composite bars.（1）Solution treatment and quenching at the room water can make the θ phase（Al₂Cu） and S phase（Al₂CuMg） phase decomposed and dissolved into the Al matrix. when the solution temperature is 495℃, with the holding solution time prolonging, θ phase and S phase dissolved more fully, so the mechanical properties of the SiC_p/2024 Al composite were also on the rise. But to 16 h, the mechanical properties of the composites were less than before, it was showed that the grain of the matrix was rough. At the same holding solution time, with increasing the solution temperature, microstructure evolution and hardness changing trend of composite appeared the same tendency with the solution treatment temperature heighten. But amplitude of variation was greater than before.it was indicated that the effect of solid solution temperature on SiC_p / 2024 Al composite was higher than the effect of holding solution time. The optimized parameters are solution treatment at 495℃for 12 hours, and then quenched at room temperature water. The typical values of tensile strength is 485 MPa, elongation is 10.3% and Brinell hardness is 158 HV. The properties of composites were greatly improved compared with those without solid solution treatment（2）The aging after solution treatment at 495℃ for 12 hours and water cooling can improve mechanical properties of SiC_p / 2024 Al composite. In the initial period of aging,the main precipitated phase was θ phase, and there is only a small amount of S phase. At the same time, hardness, tensile strength and elongation’s growth rate were small. And to 8 hours, the mechanical properties begin to increase until they reached the peaks. The S phase started to precipitate massively and the number had been beyond the θ phase. When the mechanical properties of the composite reached peaks, if it is continued to extend the holding time, the mechanical properties of the composite would reduce greatly. And the higher the temperature is, the more obvious the phenomenon is. The suitable aging treatment is for 16 h in 170℃the tensile strength is 485 MPa, the hardness reached 158 HV,and elongation decreased to 10.5%.