No Pressure Infiltration Process In Sicp / Al Composite Materials Research

High-volume SiC_p/Al composite materials have many excellent properties such as high strength,well wear resistance and good dimensional stability,so they could be used in aerospace,military weapons,cars and electronic packaging,etc.The pressureless infiltration of SiC porous performs by liquid aluminum is a simple and economic route for the production of high-volume SiCp/Al composites.We can obtain near-or net-shape composites with uniform distribution of the reinforcements and high dimensional stability by this way.However,with low chemical compatibility,SiC/Al system has poor wettability.In addition,at the pressureless infiltration temperature;there exists the potential for the development of the harmful reaction which product Al₄C₃ on the Al/SiC interface.This paper investigated the effect of the surface modification of the SiC_p,the components of aluminum alloy and all technical parameters to pressureless infiltration techniques and properties of composite materials to get better preparation process.In order to improve the wettability of SiC,we could form a coating of SiO₂ by the passive oxidation of the SiC and chemical plating of Ni respectively.Researches showed that these two methods can significantly improve the wettability of SiC/Al system,and the formation of new phases induced a strong bonding between the matrix and the reinforcement which prevented the potential production of Al₄C₃.The presence of Mg in Al matrix could promote pressureless infiltration.The main function of Mg was to reduce the content of aluminum oxide that formed on the SiC/Al interface and lower surface tension of aluminum,therefore enhanced wetting of ceramics by molten aluminum alloys.Furthermore,it has been demonstrated that silicon was a versatile element that can be used to control the harmful reactions at the Al/SiC interface.The protective atmosphere N₂ not only prevented oxidation of raw materials,but also fixed Mg in matrix.High temperature of 1100℃leaded to the break of Al₂O₃ membrane on the aluminum surface,and improved the wettability between Al and SiC particles. Infiltration for two hours could increase the relative density of SiC_p/Al composite materials up to 97 percent or more.With reduce of SiC size,the bending strength and hardness of SiCp/Al composite materials increased.Composite material made with 240^# SiC had better mechanical properties.Close connection between SiC and Al would help improve the mechanical properties of composite materials.