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Ternary MoSi2 Compounds for High Temperature Structural Applications

Published online by Cambridge University Press:  25 February 2011

S. Chin
Affiliation:
United Technologies Research Center, 411 Silver Lane, East Hartford, CT 06108
D. L. Anton
Affiliation:
United Technologies Research Center, 411 Silver Lane, East Hartford, CT 06108
A. F. Giamei
Affiliation:
United Technologies Research Center, 411 Silver Lane, East Hartford, CT 06108
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Abstract

The microstructure and phase composition of MoSi2 modified with Al, B, Ge, Hf, Nb, and Re have been investigated. B and Hf substitutions for Si and Mo, respectively, exhibited very low solubilities in MoSi2. Al and Nb substitutions for Si and Mo, respectively, changed the crystal structure from tetragonal C11b to hexagonal C40. Phase boundaries and solubility limits were determined for Al and Nb substitutions. Ge and Re substitutions for Si and Mo, respectively, exhibited complete solubility and maintained the tetragonal Cllb crystal structure. The mechanical properties evaluation as determined by four-point flexural testing indicate a ductile-to-brittle transition temperature (DBTT) of 1250-1350°C for all of the modifications evaluated. Isothermal oxidation testing at 1400°C indicates no significant debit in oxidation resistance of MoSi2 that can be attributed to alloying, however, alloys containing higher concentrations of the ternary elements may exhibit reduced oxidation resistances.

Type
Research Article
Copyright
Copyright © Materials Research Society 1994

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