Microstructural development and mechanical properties of self-reinforced alumina with CAS addition

In-situ development of platelike alumina grains were obtained by adding CAS glass powder (CaO–Al2O3–SiO2) into fine alpha alumina powder sintered in the range from 1550 to 1600°C. The sintering behavior, microstructural development and mechanical properties of self-reinforced alumina ceramics with different amount of additives were investigated. The theoretical densities of the samples sintered at 1550°C reached >97% which appeared to be the optimal sintering temperature and the addition of CAS slightly decreased the densities of samples sintered from 1300 to 1600°C, compared with the samples without CAS additive. The platelike grains were not formed in alumina ceramics without adding CAS, even sintered at 1600°C. When the 0.1∼0.5 wt.% CAS glass powder was added to the starting composition, the platelike grains were formed completely at 1550°C. The formation of platelike grains increased the fracture toughness but decreased the bending strength, the combined action of crack deflection and crack bridging accounted for the observed increase of fracture toughness. The mechanical properties decreased with increasing the sintering temperatures from 1550 to 1660°C. Adding nano γ-Al2O3 can enhance the mechanical properties of the samples sintered at 1550 and 1600°C.