Microstructure and Mechanical Properties of the in situβ-Si3N4/α'-SiAlON Composite |
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Authors: | Tzer-Shin Sheu |
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Affiliation: | Department of Materials Science and Engineering, The University of Michigan, Ann Arbor, Michigan 48109-2136 |
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Abstract: | The in situ β-Si3N4/α'-SiAlON composite was studied along the Si3N4–Y2O3: 9 AlN composition line. This two phase composite was fully densified at 1780°C by hot pressing Densification curves and phase developments of the β-Si3N4/α'-SiAlON composite were found to vary with composition. Because of the cooperative formation of α'-Si AlON and β-Si3N4 during its phase development, this composite had equiaxed α'-SiAlON (∼0.2 μm) and elongated β-Si3N4 fine grains. The optimum mechanical properties of this two-phase composite were in the sample with 30–40%α', which had a flexural strength of 1100 MPa at 25°C 800 MPa at 1400°C in air, and a fracture toughness 6 Mpa·m1/2. α'-SiAlON grains were equiaxed under a sintering condition at 1780°C or lower temperatures. Morphologies of the α°-SiAlON grains were affected by the sintering conditions. |
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