The Local Solidification Method Was Used To Prepare The Ternary Eutectic Ceramics Of Al 2 Sub-3 / YAG / ZrO 2 3

Ceramic material is the most rapidly developing high-tech material in the world. It has been developed from the traditional sintered ceramics to the directional solidification oxide eutectic ceramics, directional solidification oxide eutectic ceramic is caused wide attention of unique properties, such as excellent resistance to high temperature, anti-oxidation, corrosion resistance, high strength, and high hardness et al. It is considered as one of the most promising candidates for new ultra-high temperature structural materials, and may be used to make the ultra-high temperature aerospace engine in the future.Al2O3/YAG/ZrO2 eutectic ceramic has been prepared with zone-melting method, the research work and results are as the following:(1) The preparation and characterization of the pre-sintered ceramic samples. The ratio of raw materials is 65Al2O3/16Y2O3/19ZrO2. With the increase of sintering temperature, its bulk density increased, and its apparent porosity decreased. When it was sintered at 1500℃ for 2 hours, its density reached 3.71g/cm3, its porosity was 3.00%, its hardness was 8.85GPa, and its fracture toughness was 2.35 MPa·m1/2.(2) The preparation and characterization of the eutectic ceramic. Tungsten was chosen to be the crucible material. And the crucible internal diameter was 10mm, its wall thickness was 2mm. During the directional solidification process, the outer crucible wall temperature reached 2100℃, the crucible movement rate was 0-10mm/h, three turns plate-shape coil is the induction coil.(3) Characterization of the eutectic ceramic. The XRD pattern shows that the eutectic consists of A12O3 phase YAG phase and ZrO2 phases, the same phases composition as in the pre-sintered ceramics,and three phases all grew as preferred orientation. SEM shows that the microstructure of eutectic is typical " Chinese script" structure, YAG was the matrix phase of eutectic ceramics, AI2O3 phase embedded in the matrix phase uniformly in non-continuous. And ZrO2 phase distribute in Al2O3 phase and the interface between YAG phase and Al2O3phase.(4) Effect of growth rate on microstructure and machanical properties of eutectic ceramic. With the increase of growth rate, the microstructure is finer, by measuring and calculated λ2v≈100 conform to the λ2v=constant. With the increase of growth rate, themachanical properties increase gradually, the hardness of eutectic ceramics was 16.24GPa, fracture toughness was 3.01 MPa·m1/2, which was 1.83 and 1.28 times ofpre-sintered ceramic, respectively. The disappearance of the pore and the interface non-crystal phase and the single crystal phase can effectively improve the hardness and fracture toughness of the material. The distribution of ZrO2 phase plays a role in the crack bridging, crack deflection, crack branching, crack pinning and other toughening effects.