Paper number 511


M. Yoshida1, K. Nagahisa2, J. Pan1, G. Sasaki1, and H. Fukunaga1

1Department of Mechanical Engineering, Hiroshima University, Kagamiyama 1-4-1, Higashi-Hiroshima, 739-8527, Japan
2Graduate school of Hiroshima University

Summary As a potential material for high temperature services, the mechanical properties and microstructure of the directionally solidified oxide eutectic alloys have been investigated. Currently, Waku et al. fabricated D.S. Al2O3-YAG eutectic composites. In this study, to improve the fracture toughness of this composites, the test specimens of SiC whisker or fiber / Al2O3-YAG composites were prepared by arc-melting or high frequency melting. In order to determine the chemical reaction between ?SiC and eutectic liquid phase, EPMA, XRD and MDG analyses were carried out. As a results, the following reaction was estimated.
Al2O3 + YAG + SiC <=> Al(liq.) + Si(liq.) + (Si, Y) Carbide + CO(gas)
To prevent ?SiC from oxidization, it is found that the pressure of CO gas should be larger than 4.43 atm at 2373 K. On the mechanical properties of the composites, micro-Vickers hardness, Hv of the Al2O3-YAG and the SiCw/ Al2O3-YAG composites are 1450 and 1680 respectively. The estimated fracture toughness K1C of the composites by the indentation fracture method was approximately 9 MPa.m0.5.
Keywords ceramics composite, SiC, alumina, YAG, eutectic, solidification.

Theme : Metal Matrix Composites ; Microstructure/Properties Relationship

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