Mechanical behavior of MoSi sub 2 reinforced-Si sub 3 N sub 4 matrix composites

The mechanical behavior of MoSi sub 2 reinforced-Si sub 3 N sub 4 matrix composites was investigated as a function of MoSi sub 2 phase content, MoSi sub 2 phase sizes, and amount of MgO densification aid for the Si sub 3 N sub 4 phase. Coarse-phase MoSi sub 2 -Si sub 3 N sub 4 composites exhibited h...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 1997-12, Vol.80 (12), p.3070-3076
Main Authors: Petrovic, J J, Pena, M I, REimanis, I E, Sandlin, M S, Conzone, S D, Kung, H H, Butt, D P
Format: Article
Language:English
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Summary:The mechanical behavior of MoSi sub 2 reinforced-Si sub 3 N sub 4 matrix composites was investigated as a function of MoSi sub 2 phase content, MoSi sub 2 phase sizes, and amount of MgO densification aid for the Si sub 3 N sub 4 phase. Coarse-phase MoSi sub 2 -Si sub 3 N sub 4 composites exhibited higher room-temperature fracture toughness than fine-phase composites, reaching values > 8 MPam exp 1/2 . Composite fracture toughness levels increased at elevated temperature. Fine-phase composites were stronger and more creep resistant than coarse phase composites. Room-temperature strengths > 1000 MPa and impression creep rates of approx10 exp -8 s exp -1 at 1200 deg C were observed. Increased MgO levels generally were deleterious to MoSi sub 2 -Si sub 3 N sub 4 mechanical properties. Internal stresses due to MoSi sub 2 and Si sub 3 N sub 4 thermal expansion coefficient mismatch appeared to contribute to fracture toughening in MoSi sub 2 -Si sub 3 N sub 4 composites.
ISSN:0002-7820