Synthesis, microstructural analysis and mechanical properties of alumina-matrix cermets

Al^sub 2^O^sub 3^ matrix cermets have been produced from mechanically mixed powders containing different metals (Al, Fe or Ti) as reinforcements. The powder mixture was compacted to cylindrical samples, which were subjected to pressure-less sintering 1500 °C for 1 h. Microstructure of the sintered bodies was studied by optical and electron microscopy. It was found that microstructure of cermets with Al and Fe consisted of equally distributed metallic particles in the Al^sub 2^O^sub 3^ matrix. However, cermets with Ti reinforcement were characterized by a metallic network interconnected with the matrix material. The relative densities of the Al-, Fe- and Ti-containing cermets in order were 93%, 93.5% and 87.3%, respectively. These densities and the microstructure of particular cermets most probably make possible to produce composites with small elastic modulus and improved fracture toughness. It was concluded that incorporation of a ductile metal into a hard ceramic matrix improves its fracture toughness. The probable toughening mechanism is crack bridging due to the homogeneous distribution of ductile metal in the microstructure of cermets. [PUBLICATION ABSTRACT]