Study On Microstructure And Property Of Si_p/Al Composite With High Volume Fraction Of Si

Si_p/Al composites with high volume fraction of Si are provided with light weight, high strength, low thermal expansion coefficient and good wear resistance and other characteristics. This is a new structural and functional materials with a wide range of applications of electronic packaging and lightweight vehicles and other fields. In this article Si_p/Al composite with high volume fraction of silicon was prepared by pressure infiltration method. Then isothermal heat treatments were conducted on Si_p/Al composites to improve the morphology of Si particles and the interfacial bonding between Si particles and the aluminum matrix. The results and conclusions are as follows:(1) The microscopic characteristics of Si_p/Al composites prepared by pressure infiltration method were studied. The results show that density of Si_p/Al composites is 2.1-2.6g/cm3 and the volume fraction of silicon is between 52%-74%. Si particles distribute uniformly in the matrix alloy. Loose defects mainly exist in narrow slit between the silicon particles, and gradually increased from the top to the bottom. Process of dissolution and diffusion of silicon from silicon particles to aluminum occurre during pressure infiltration method. Sharp edges of Silicon particles have passivation tendency. Some silicon phase precipitates in the silicon particle surface. The closer to the top of Si_p/Al composite, the improvement of silicon particle morphology and interfacial bonding are more obvious.(2) The effect of particle size and matrix alloy to Si_p/Al composites microstructure was studied. The results show that loose defects of Si_p/Al composites decrease with the increase of diameter of the Si phase and content of silicon in the matrix alloy. Using the average diameter of the silicon particles of about 100μm and ZL102 alloy for pressure infiltration method, dense of Si_p/Al composites is optimal.(3) Impact of isothermal treatment on the Si_p/Al composites microstructure was studied. The results showed that loose defects in Si_p/Al composites decrease after isothermal heat treatment at 560℃-600℃ for 30min-70min. Morphology of silicon particles and combination of and Al-Si interface are also improved. Loose defects of material decrease with the growth of temperature and isothermal isothermal time. Isothermal treatment temperature exceeds 600℃ for more than 50min can easily lead to an increase of loose defects and grain coarsening.(4) The effect of particle size of silicon and matrix alloy on Si_p/Al composites thermal expansion coefficient was studied. The results show that the thermal expansion coefficient of Si_p/Al composite prepared by infiltration method range between 10.1×l0-6/K and 13.6×10-6/K. Thermal expansion coefficient of Si_p/Al composites increases with the increase of silicon particle diameter, decreases along with the increase of silicon content of matrix alloy.