THE EFFECT OF FABRICATION TECHNIQUES ON THE PROPERTIES OF AL-SIC COMPOSITES

This study focusses on silicon carbide particulate-reinforced metal-matrix composites fabricated using four different powder metallurgy techniques. The effect of the fabrication method on the mechanical properties of the near net shape specimens was investigated. Sinter/hot isostatically pressed (sinter/HIPed) composites of up to 30 vol.% SiC were produced with a significant improvement in ductility and ultimate tensile strength compared with the other fabrication methods. The poor mechanical properties of composites produced by the other methods is attributed to the weak bonding between adjacent particles and to internal porosity. The measured densities of the fabricated materials indicated that fully dense material was not achieved. For composites with less than 10% volume fraction of SiC, the density was relatively independent of the fabrication method adopted. Microstructural examination of fracture surfaces in representative materials confirmed that the sinter/HIPing technique yielded the best composites. For particle loading less than 10% volume fraction, ductile failure of the matrix appears to be the limiting factor. At higher volume fractions, the strength of interfacial bonds, initiation and growth of voids, and particle cracking all play an important role in controlling the mechanical properties.