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 t he range from 1550 to 1600 degreesC. The sintering behavior, microstructura l development and mechanical properties of self-reinforced alumina ceramics with different amount of additives were investigated. The theoretical dens ities of the samples sintered at 1550 degreesC reached >97% which appeared to be the optimal sintering temperature and the addition of CAS slightly de creased the densities of samples sintered from 1300 to 1600 degreesC, compa red with the samples without CAS additive. The platelike grains were not fo rmed in alumina ceramics without adding CAS, even sintered at 1600 degreesC . When the 0.1 similar to0.5 wt.% CAS glass powder was added to the startin g composition, the platelike grains were formed completely at 1550 degreesC . The formation of platelike grains increased the fracture toughness but de creased the bending strength, the combined action of crack deflection and c rack bridging accounted for the observed increase of fracture toughness. Th e mechanical properties decreased with increasing the sintering temperature s from 1550 to 1660 degreesC. Adding nano gamma -Al2O3 can enhance the mech anical properties of the samples sintered at 1550 and 1600 degreesC. (C) 20 01 Elsevier Science Ltd. All rights reserved.