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

This study focusses on silicon carbide particulate-reinforced metal-ma trix composites fabricated using four different powder metallurgy tech niques. The effect of the fabrication method on the mechanical propert ies of the near net shape specimens was investigated. Sinter/hot isost atically pressed (sinter/HIPed) composites of up to 30 vol.% SiC were produced with a significant improvement in ductility and ultimate tens ile strength compared with the other fabrication methods. The poor mec hanical properties of composites produced by the other methods is attr ibuted 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 independen t of the fabrication method adopted. Microstructural examination of fr acture surfaces in representative materials confirmed that the sinter/ HIPing technique yielded the best composites. For particle loading les s than 10% volume fraction, ductile failure of the matrix appears to b e the limiting factor. At higher volume fractions, the strength of int erfacial bonds, initiation and growth of voids, and particle cracking all play an important role in controlling the mechanical properties.