| High-volume fraction SiCp/Al combined the excellent characteristics of SiC with Al such as low density, high strength, low thermal expansion coefficient and high thermal conductivity properties. Therefore, they have been widely used in many areas, especially in aerospace. At present,The method of preparing high volume fraction SiCp/Al composites are mainly powder metallurgy, stir casting, non-pressure impregnation method, pressure infiltration, injection molding, etc., the preparation process is complex and costly.Compared with many other manufacturing processes, pseudo-semi-solid extrusion process with near net shape capability, less equipment investment and other advantages. In this paper,using pseudo-semi-solid extrusion successfully prepared SiCp/Al composites.Study on the dependence of SiC grain composition pore-forming agents and interface features with the properties of composite. The infiltration process and infiltration mechanism of SiCp/Al composites were analyzed by metallurgical microscope, Scan Electron Microscope (SEM), Transmission Electron Microscope(TEM), X-Ray diffraction (XRD). Energy Dispersion Spectrometer (EDS) and other techniques. The mechanical and thermal properties of SiCp/Al composites were researched systemically and thoroughly, the relationship between SiC content, grain composition, structure of composites and their properties was revealed, which provides practical and theoretical basis to prepare low cost, low thermal expansion coefficient and high thermal conductivity SiCp/Al composites.The process combined the features of powder metallurgy technology and semi-solid metal processing technology, The main features are as follows:(1)It can achieve near the end of the molding materials to avoid shrinkage composite materials and to reduce the amount of parts for machining.(2) Avoid leaving microscopic holes in SiC and Al matrix interface by using powder metallurgy process.(3) When the pseudo-semi-solid forming, It can reduce the viscosity between SiC and Al,because there are blanks in the presence of molten liquid metal exists, and it makes metal have good liquidity, easily forming.Thus through improved technology, it can achieve automated manufacturing.(4) complex shapes can be produced,because the flow stress of pseudo-semi-solid forming is low and extrusion speed is high.(5) pseudo-semi-solid forming temperature is relatively low and the temperature of base metal is nearly of the melting point.It released latent heat of crystallization and reduced the mold thermal shock and increased the life of the mold.The SiCp/Al composite materials of SiC volume fraction of40%,50%and65%was prepared by Pse-udo semi-solid extrusion technology and Its microstructure and pro-perties were studied. The results showed that silicon carbide particles of the pre-paration of high volume fraction of SiCp/Al composite distributed evenly.not only Small SiC particles embedded in the aperture of SiC particles but also Al substrate filling in the aperture of SiC particles,and they formed a dense tissue. Mg and SiO2can improve interface wettability between SiC particles and Al.they also can increase the interface bonding strength of SiC particles and Al. The preparation of the silicon carbide volume fraction of65%of the composite material density is3.11g/cm3, surface hardness of HB is108.5, flexural strength is302.1MPa, thermal expansion rate is less than5.6×10-6/K, thermal conductivity is74W/mK.The destruction between the SiC and Al contains both understand cleavage fracture, the matrix plastic fracture, also includes interfacial debonding crack. |
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