A ductile ceramic eutectic composite with high strength at 1,873 K
A ductile ceramic eutectic composite with high strength at 1,873 K
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DOI：
10.1038/37937
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发表时间：
1997-09
期刊：
影响因子：
64.8
通讯作者：
Y. Waku;N. Nakagawa;T. Wakamoto;H. Ohtsubo;K. Shimizu;Y. Kohtoku
中科院分区：
文献类型：
--
作者：
Y. Waku;N. Nakagawa;T. Wakamoto;H. Ohtsubo;K. Shimizu;Y. Kohtoku
Monolithic ceramics are not widely used as structural materials because of their brittleness. Ceramic matrix composites, in which whiskers 1, 2, 3 or fibres 4, 5, 6, 7 of strong ceramics such as silicon carbide or silicon nitride are embedded in a ceramic matrix, offer improved toughness and strength because the energy of cracks may be dissipated at the whisker/matrix interface. Here we describe a strong ceramic composite with a different kind of microstructure, made by unidirectional solidification of an Al 2 O 3/GdAlO 3 eutectic mixture. This composite has a microstructure in which continuous networks of single-crystal Al 2 O 3 and single-crystal GdAlO 3 interpenetrate without grain boundaries. Rather than brittle fracture, the material displays plastic deformation at 1,873 K owing to dislocation motion, as in metals. The high strength and resistance to brittle failure of this material at such high temperatures augurs well for applications in mechanical engineering.Microstructural studies on an Al 2 O 3/Y 3 Al 5 O 12 (YAG) system using the Bridgman method show that the microstructure of this composite can be controlled by unidirectional solidification 8. It has been reported that a unidirectionally solidified Al 2 O 3/YAG eutectic composite has superior flexural strength, thermal stability and creep resistance at high temperature 9, 10, 11, and is a candidate for a high-temperature structural material. However, this material contains many grain boundaries or colonies between Al 2 O 3 and YAG, which are expected 12 to impair the mechanical properties. Waku et al. 13, 14, 15 have recently fabricated a eutectic composite consisting of single-crystal Al 2 O 3 and single-crystal YAG with neither colonies nor grain boundaries, using a unidirectional solidification. The composite is thermally stable and its flexural strength at room temperature can be maintained up to 2,073 K, which is just below the melting point (∼ 2,100 K). In addition, the compression creep strength at 1,873 K and a strain rate of 10− 4 s− 1 is∼ 13 times higher than that of sintered composites with the same composition, and the material shows neither weight gain nor grain growth even on heating at 1,973 K in air for 250 hours.
