Processing of Al-SiC_p Metal Marix Composites by Pressureless Infiltration of SiC_p Preforms

摘要

. An optimum method for producing AI-SiCp metal matrix composites was developed by determining the optimum conditions for wetting SiC by aluminum and the optimum parameters for pressureless infiltration of SiCp preforms. The quantitative effect of magnesium and silicon additions to aluminum, free silicon on the SiC substrate, nitrogen gas in the atmosphere, and process temperature on the wetting characteristics of SiC by aluminum alloys was investigated using the sessile drop technique. The contribution of each of these parameters and their interactions, in terms ofa relative power, to the contact angle, surface tension, and driving force for wetting were determined. In addition, an optimized process for enhanced wetting was suggested and validated. The optimum conditions for wetting SiC by aluminum that were arrived at were used to infiltrate SiCp preforms and the mechanical properties of the resulting metal matrix composites were measured. The effect of SiC particle size, infiltration time, preform height, vol. % SiC in the preform, and Si coating on the SiC particles Qn the pressureless infiltration of SiCp compacts with aluminum was investigated and quantified. The contribution of each of these parameters and their interactions to the retained porosity in the composite, the modulus of elasticity, and the modulus of rupture were determined. Under optimum infiltration conditions, metal matrix composites with less than 3% porosity,. over 200 GPa modulus of elasticity, and about 300 MPa modulus of rupture were routinely produced.