Preparation And Properties Of Al₂O₃/ZrO₂/YAG Composite Powders And Ceramic With Eutectic Composition

In this project, Al₂O₃/ZrO₂/YAG eutectic composition precursors was proposed by ethanol/water co-precipitation. This present work concentrates on the effect of cation concentration, pH, dispersant and aging time on the precursor powders morphology and dispersion. The precursor morphology and the process of phase transition was characterized by SEM,TG-DTA and XRD. Al₂O₃/ZrO₂/YAG eutectic composite powder was fabricated by calcining the prepared particle with sizes of 300 nm in diameter. The phase structure that α-Al2O3 particles embraced c-ZrO2 particles was constructed,confirmed by TEM.The Al₂O₃/ZrO₂/YAG composition ceramics was prepared by hot pressing method.The hot pressing curve indicated that the fastest densification temperature of the ceramics is 1500 o C. Ceramics was sintered at the temperature in the range of1400oC-1600 o C. Intragranular ceramic phases were distributed uniformly. Ceramics sintering at the temperature of 1500 oC and 1550 oC have been prepared with the crystal structure that α-Al2O3 particles embraced c-ZrO2 particles.Mechanical properties were tested for composite ceramics sintering in different temperatures. The ceramics which was sintered at 1550 oC has the best comprehensive performance. The density, temperature flexural strength, high temperature flexural strength（1000oC）, fracture toughness reached 98.8%, 419 MPa, 464 MPa, 3.69MPa·m1/2,separately. Combined with the fracture and crack propagation path results, the crack deflection, crack branching, intragranular crystalline strengthening toughening mechanisms have been found.Al₂O₃/ZrO₂/YAG eutectic ceramics have been prepared by high-temperature melting at 1700 oC and 1800 oC. The eutectic ceramic prepared at 1700 oC consists ofα-Al2O3, c-ZrO2 and YAG, while that consists of α-Al2O3, c-Zr O2 and YAP prepared at1800 oC. The eutectic ceramic prepared at 1700 oC has better properties. Study the effects of different body using in melting. Melting by sintered body can effectively improve the performance of the eutectic ceramics. Al₂O₃/ZrO₂/YAG eutectic ceramic has a good hot stability at 1450 oC. At 1650 oC, the microstructure of the eutectic ceramics start to coarsing.