| Sip/Al composite with high silicon content is a new type of structural and functional material which has good wear-resistance, high volume stability and low thermal expansion coefficient. Sip/Al composite has a wide application in automobile engine, plunger, electronic packaging materials and other fields. In this paper, Sip/Al composite with high volume fraction of silicon was prepared by penetrating casting. And the Sip/Al composite with more than30%volume fraction of silicon was prepared by remelting the Sip/Al pre-fabricated block in aluminum. Then, isothermal treatments were conducted on the Sip/Al composites prepared by different process to modified the shape of silicon particles and to improve the bonding between the silicon particles and the matrix in the composite. The results and conclusions are as follows:(1) The infiltrating process was studied to prepare the Sip/Al composite with high volume silicon by using different size of silicon particles. The results show that the main factors which influence penetrating casting are the preheat temperature of silicon particles, the pouring temperature of aluminum and the penetrating pressure. The optimum range of the parameters such as preheat temperature of silicon particles, the preheat temperature of silicon particles, pouring temperature of aluminum and the penetrating pressure are obtained by experiments. They are respectively is560℃～620℃.700℃～750℃, and0.3MPa～0.4MPa. The volume fraction of silicon particles in the Sip/Al composite prepared is52%～74%.(2) The influence of isothermal treatment on the microstructure of the Sip/Al composite prepared by penetrating casting was studied. The results show that heating the composite at580℃～600℃for15min～20min can effectively improve the morphology of silicon particles. The irregular polygonal block silicon particles are gradually transformed to that of nearly spherical shape, and the eutectic silicon in the composites is also changed from acicular shape to spotted shape. Furthermore, the tiny shrinkage defects in the composite matrix are eliminated after isothermal treatment.(3) The Sip/Al composite with relatively low silicon content of silicon was faburicated by means of diluting Sip/Al precast block in aluminum melt. Firstly, a proportion of Sip/Al precast block is added to the pure aluminum melt and heated to about720℃. Then, the melt is treated by high-energy ultrasonic after it cooling to 680℃～700℃. After solification, the Sip/Al composite with silicon content more than30%can be prapered. The dense structure, well bongding between silicon particles and matrix as well as dispersed silicon with small size are obtained in the composite prepared.(4) The isothermal treatment was conducted on the Sip/Al composite which prepared by means of diluting pre-cast composite block in aluminum melt. The influence of isothermal treatment on the microstructure of the Sip/Al composite was studied. The results show that heating the composite at580℃～600℃for l0min～20min can effectively improve the morphology of silicon particles. But the size of silicon particles in the composite is not changed apparently after treatment. |
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