Microstructure and Properties of Al_2O_3-ZrO_2 Ceramics Prepared by Microwave Sintering

摘要

ZrO_2 doped with 7.5% (volume percent) nano-alumina ceramics were prepared by microwave sintering processes. The effects of nano-alumina additions and various sintering temperature on densification, phase composition, microstructure and mechanical properties of AI_2O_3-ZrO_2 ceramics were investigated. The results show that the m-ZrO_2 phase transformed into t-ZrO_2 during the process of microwave sintering. Relative densities between 95% and 99% were attained in the different conditions. In any cases the grain size was maintained at a submicron scale at a processing microwave sintering. The presence of AI_2O_3 grains had an effect of hindering grain growth of ZrO_2 grains. When the microwave sintering temperature was 1500°C, 7.5AI_2O_3-ZrO_2 composite ceramics presented excellent mechanical properties: HV=12.0 GPa, σ_f=715.7 Mpa, K_(IC)= 1.9 MPam~(1/2). Compared with that of pure ZrO_2 ceramic, the bending strength and the fracture toughness were improved 45% and 23% at least, respectively. The fracture mode was associated with sintering temperature: when the sintering temperature was 1350°C~1450°C, the intergranular fracture and transgranular fracture coexisted; when the sintering temperature was 1500°C, intergranular fracture was the main fracture mode.