α-SiC particles have been processed with surface treatment of high-temperature calcination and water washing technology. SiCp/Al-30Si composite has been prepared in the vacuum hot extrusion process. The powder morphology and specimens microstructure have been observed using scanning electron microscopy, the phase of SiC has been analyzed using the X-ray diffraction. Meanwhile, the tensile strength and thermal expansion coefficient of the composite have been tested. The effects of the morphology of the SiC particles, tensile strength and thermal expansion coefficient have been studied on composite microstructure. The consequences show that, after the surface treatment SiCp/Al-30Si composite，the interfaces combined with matrix are in a better condition and less holes, the tensile strength of composite materials has been improved significantly, the coefficient of thermal expansion becomes lower than before.

This paper studied the combined effects of particle size and distribution on the mechanical properties of the SiC particle reinforced Al-30Si alloy composites. The microstructure of experimental material was analyzed by SEM, the tensile strength and physical properties were examined. The results show that, with the increase of the SiC particle size in the composites, the clustering degree of the SiC particles decreases in the matrix, the SiC particles distribute more ununiformly. The tensile strength is influenced by the SiC particle size, the tensile strength of the composite reinforced by 13μm sized SiC particles is the highest.

The SiCp/Al-30Si composite material was prepared by hot-pressing. The microstructure was characterized by means of optical microscope and SEM, the thermal expansion performance was tested by PYC-Ⅲ Thermal Expansion Coefficient Tester. It was researched that the influence of SiC particle size and manufacture technology on the microstructure and thermal expansion coefficient. Results show that shortening soaking time decreases the number and the size of the nascent and precipitating Si particles, enlarges the CTE of the composite; lager pressure is beneficial to reduce the CTE of the composite, and the larger the pressure is, the more compact microstructure is and the less number of holes are. Thermal expansion performance of the composite was influenced by SiC particle size, distribution of matrix phase, trait of interface combination and the holes.