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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.48  No.9 (2007)  >  pp.2312-2315

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Effects of Shaping Conditions on the Microstructure and the Mechanical Property of the Al2O3-YAG Eutectic Composite Produced by Melting the Al2O3-YAP Eutectic Structure

Tomoya Nagira, Hideyuki Yasuda, Takumi Sakimura and Asako Kawaguchi
1) Department of Adaptive Machine System, Osaka University

When the Al2O3-YAP metastable eutectic system was heated above the metastable eutectic temperature but below the equilibrium eutectic temperature, undercooled melt was formed. Solidification in the equilibrium path accompanied the melting of the metastable eutectic system, resulting in a fine and uniform eutectic structure. A novel solidification process using undercooled melt formation was developed. In this paper, the influences of the initial Al2O3-YAP eutectic particle size, forming pressure and holding time at the maximum temperature on the microstructure and/or the mechanical property of the Al2O3-YAG compact were examined to optimize the forming conditions. The Al2O3-YAG compact produced from the Al2O3-YAP eutectic particles with diameters less than 20 μm exhibited a higher flexural strength and the smaller porosity as compared to that produced from Al2O3-YAP eutectic particles with diameters ranging from 20 μm to 45 μm. The volume fraction of the porosity was approximately 4% under a forming pressure of 10 MPa and a holding time of 60 s. The flexural strength of the Al2O3-YAG compact decreased with the increase in the holding time due to the increase in the lamellar spacing. For Al2O3-YAP eutectic particles with diameters less than 20 μm, a low forming pressure of 10 MPa and a short holding time of 60 s were sufficient to synthesize a dense Al2O3-YAG compact. Thus, the solidification technique that uses undercooled melt produced by melting the Al2O3-YAP metastable eutectic system has good advantages for shaping.

undercooled melt, eutectic ceramics, eutectic solidification, nucleation

Received: March 22, 2007
Accepted: April 11, 2007 , Published online: August 25, 2007
Copyright (c) 2007 The Japan Institute of Metals



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