Microstructure evolution in densification of SiC ceramics by aluminium vapour infiltration and investigation of mechanical properties

The densification and phase formation of 6 wt% Y2O3 containing SiC compacts infiltrated by aluminium vapour were investigated. The densification occurred through infiltration of aluminium vapour that formed through a reaction between alumina and carbon powders at 2000 °C. Infiltrated specimens were evaluated concerning the density, phase, microstructure and mechanical properties including hardness and fracture toughness. X-ray diffraction studies showed the presence of yttrium aluminium garnet (YAG) and Al2O3 as the secondary phases along with other minor phases. Sectioning of the infiltrated specimen showed two regions: a dense layer starting from the surface of about 1 mm thickness followed by a relatively porous structure at the core. The effect of infiltration depth on densification and evolution of microstructure are studied. Also, the changes in Vickers' hardness and fracture toughness with the increase in specimen depth are discussed.