Directionally solidified Al 2 O 3 /ZrO 2 eutectic ceramic prepared with induction heating zone melting
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To prepare high quality large solidified Al2O3/ZrO2 eutectic ceramic, the preparation processing of the presintered ceramic as a feed rod was investigated via experiments; some parameters of the induction heating zone process were optimized via numerical modeling; an Al2O3/ZrO2 eutectic ceramic rod with a diameter 10 mm was prepared. The results show that increasing the sintering temperature could increase the presintered ceramic’s bulk density, while increasing sintering time had little effect. And the bulk density increased first and then decreased with the molding pressure increase. And the saucer coil obtained a higher temperature gradient than the tubbiness coil for a fixed crucible wall maximum temperature, and the coil turn’s increase could increase the melting zone height in the induction zone melting process. In the directionally solidified Al2O3/ZrO2 eutectic ceramics, Al2O3 phase is the matrix phase, and the ZrO2 phase embedded in the Al2O3 phase mostly with the rod shape, and little with lamellar. The hardness of directionally solidified eutectic ceramics reaches 16.17 GPa and the fracture toughness reaches 4.76 MPa m1/2, which are 1.7 times and 1.5 times of the presintered eutectic ceramic, respectively.
I. INTRODUCTION
Directionally solidified eutectic oxide ceramics are promising to be a new generation of ultra high temperature structural materials for aerospace engines due to their unique high temperature mechanical properties and ablation resistance. Since the 21st century, the demand for ultra high temperature ($1650 °C) materials has being become more and more urgent with the rapid development of the aerospace industry. Ultra high temperature materials with excellent properties could make the engine and turbine work normally at ultra-high temperature without a cooling system, thus promote fuel combustion and reduce consumption and harmful emissions. Compared with the high-performance ceramics prepared by the traditional sintering method, there are no pores and interface amorphous phases in the directionally solidified eutectic ceramics, thus the material’s mechanical properties improve greatly, especially at high temperatures, thus is very promising to be a new generation of ultra high temperature structural materials.1 In recent years, scholars from various countries have carried out a lot of research studies. They prepared directionally solidified eutectic ceramics with different experimental methods. In 1997, Waku et al.2–4 prepared an Al2O3/ Y3Al5O12 (YAG) eutectic ceramic with excellent high temperature performance using an improved Bridgeman a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.113
method. This ceramic’s tensile strength at 1700 °C was up to 160 MPa, and its elongation was up to 10%. At 1600 °C, the material was applied 104/s strain rate; its creep strength could be as high as 433 MPa, which is 13 times of the sintered ceramic with the same composition. After zirconia doping, Al2O3/Y2O3/ZrO2 eutectic ceramics had the flexural strength at 1
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