Fabrication of low-shrinkage reaction-bonded alumina−mullite composites

Low-shrinkage alumina−mullite composites were fabricated by reaction bonding using α-Al2O3, Al, β-SiC and 3Y-ZrO2 as the starting powders. The effects of ZrO2 addition and sintering temperature on densification behaviour and mechanical properties were investigated. It is shown that the addition of ZrO2 can effectively inhibit grain growth and significantly accelerate densification. At a sintering temperature of 1580°C, 15 vol.% ZrO2-containing alumina−mullite composites were sintered to 97.4% of the theoretical density. Due to a relatively homogeneous microstructure without large abnormal grains, such composites exhibited a highly intergranular fracture mode. As a result, a high strength up to 575 MPa was obtained.