Fabrication and mechanical properties of in situ formed carbide particulate reinforced aluminium composite

Abstract

Stable carbide particles of TiC, ZrC and TaC were in situ synthesized in liquid aluminium by the reaction between Al-Ti, Al-Zr or Al-Ta systems liquid alloy and SiC or Al₄C₃ particles. It was possible to generate TiC particles of nearly 1 μm diameter, even utilizing SiC of 14 μm. However, the dispersion behaviour of TiC particles in the matrix depended on the size of the raw carbide. Finer SiC made the dispersion of TiC particles more uniform, resulting in a greater improvement of the mechanical properties. Furthermore, although Al-Ti-Si system intermetallic compound was detected in a TiC_p/Al-Si composite fabricated by the melt-stirring method, those compounds considerably decreased in the composite fabricated by the in situ method. The mechanical properties of in situ formed TiC_p/Al-5 wt% Mg and TiC_p/Al-5 wt% Cu composites were better than those fabricated by the melt-stirring method and by T6 heat treatment, the properties of in situ formed TiC_p/Al-5 wt% Cu composite were further improved. The experimental results were analysed by the reaction model based on the assumption that the overall reaction rate was controlled by both the reaction and the diffusion.