Preparation Of SiCp/Al Composites By Pressureless Infiltration

SiCp/Al composites have high thermal conductivity (TC), low coefficient of thermal expension (CTE), high specific stiffness and high thermal stability. In this article, SiCp/Al composites were prepared by pressureless infiltration. Impacts of artificial pre-oxidation, matrix alloys, preform porosities and heat histories on properties of the SiCp/Al composites were investigated. The microstructures, mechanical and thermal properties of the composites were studied by OM, XRD, LFA and DIL.Using different content of graphite and different ratio of SiC powders (50μm and 10μm) to obtain desired preform porosities.The artificial pre-oxidation of SiC preforms by high purity oxygen can add a thin layer of a-SiO2 on the silicon carbide which increase compressive strength of SiC performs and enhances the wetting of SiC by aluminum alloy. As silicon content reached llwt%, XRD patterns showed there is no sign of the formation of the unwanted intermetallics Al4C3. The content of Mg also has an impact on the retained porosity of the composites, thus has an impact on the compressive strength of the SiCp/Al composites. The artificial pre-oxidation preform with 40% porosity was infiltrated with Al-11wt%Si-6wt%Mg alloy under high purity nitrogen atmosphere at 1100℃, holding time 1h. OM showed uniformly dispersed SiC particles in the aluminum matrix. The apparent density of the composite was evaluated using Archimede's method, so the retained porosity of the composite was also determined. The compressive strength of the composite reaches 367MPa, microhardness reaches Hv 100164, thermal conductivity reaches 121W/mk, and coefficient of thermal expansion reaches 9.2×10-6℃.