Effect of Mg and Si in the aluminum on the thermo-mechanical properties of pressureless infiltrated SiCp/Al composites

The effect of adding Mg and Si to aluminum on the thermo-mechanical properties of pressureless infiltrated SiCp/Al composites was investigated. The results showed that, when the Si content was lower than 6 wt% or the Mg content was lower than 4 wt%, the composites showed poor thermo-physical properties because of higher porosity in the composites resulting from the poor wettability between Al and Si. Increasing the Si content to the aluminum can enhance the elastic modulus, thermal dimensional stability and thermal conductivity of the composites and reduce the coefficient of thermal expansion (CTE) of the composites. However, excessive Si beyond 12 wt% can reduce the thermal conductivity and bending strength of the composites. An optimum content of Mg addition to aluminum was found to be 4-8 wt%, at which the composites exhibited good thermo-mechanical properties. However, as the Mg content was increased beyond 8 wt%, the higher porosity in the composites resulting from the lower pressure of the magnesium led to lower thermo-mechanical properties. The microstructure of such composites was also studied by SEM and TEM to better understand how the addition of Si and Mg affects their properties. (c) 2006 Elsevier Ltd. All rights reserved.