Investigation On Preparation And Properties Of New-Style Al-Si Composites

In the present paper, a new-style Al-Si composite, which possesses less density and lower expansion coefficient, was fabricated by the method of pressure infiltration combined with hot extrusion. The processing parameters of pressure infiltration and hot extrusion were confirmed. The influences of the processing parameters on the formability, the microstructure and the properties of Al-Si composites were discussed. The pressure infiltration mechanism was studied systematically by combining with the theoretic calculation. The main conclusions are presented as follows.1. High-performance Al-Si composite can be fabricated successfully by the method of pressure infiltration combined with hot extrusion. Its thermal expansion coefficient is 8～10×l0~6/℃, the density 2.48g/cm~3, the compresive strength 217.5 MPa, and the extensibility 1.45%.2. The wettability in the Al-Si system can be improved by elevating the infiltration temperature and elongating the infiltration time properly, which are helpful to form the network structure in the aluminum matrix.3. There are a large numbers of eutectic phases and some coarse, strip Si particles, which lead the mechnical property to worsen seriously, in Al-Si composite fabricated by single pressure infiltration. The eutectic phases and coarse, strip Si particles can be decreased by sequential hot extrusion, and the mechnical property of Al-Si composites can be improved remarkably.4. The XRD results show there is no metal oxides formed in Al-Si composites, and indicate that Al-Si composites can be prepared in no protective atmosphere.5. If the precast body is undeformed, the ratio between the Si reinforced particles and the aluminum matrix can be adjusted freely to obtain the high-performance Al-Si composite during the course of pressure infiltration6. The results of theoretical calculation and the experiments show that the actual infiltration pressure is larger than that of the theoretical calculation, which can be attributed to the simplification of the calculating model and the neglect of the air pressure in precast body in the course of pressure infiltration.