Study of the effects of Al, Ta, W additions on the microstructure and properties of MoSi{sub 2} base alloys
- Univ. of Surrey, Guildford (United Kingdom). Dept. of Materials Science and Engineering
Solidification microstructures and phase selection in ingots and melt-spun ribbons of MoSi{sub 2}, MoSi{sub 2}-W-Ta and MoSi{sub 2}-Al alloys were studied. Rapid quenching from the melt refined the grain size of all alloys by two orders of magnitude compared to the ingots. Zone A microstructures were formed in the wheel side of all alloy ribbons. Addition of an Ta and of Al suppressed the formation of Mo{sub 5}Si{sub 3} in the ingots and ribbons. Tungsten exhibited complete solid solubility in MoSi{sub 2}. In the ribbons the solubility of Ta in MoSi{sub 2} was extended to 2 at% in Zone A, and in the ingots and zone B of the ribbons hexagonal (C40) TaSi{sub 2} and tetragonal (C11{sub b}) MoSi{sub 2} structures were formed. A fine lamellar microstructure between the C11{sub b} and C40 phases was formed at 1,350 C after 48h. Addition of Al changed dramatically the solidification microstructure which consisted of two phases C40 Mo(Al{sub 0.5}Si{sub 0.5}){sub 2} and C54 MoAl{sub 1.3}Si{sub 0.7}. In the ingots the room temperature hardness decreased with addition of W and Ta and of Al. Addition of Al increased the thermal stability of the MoSi{sub 2}-Al alloy.
- OSTI ID:
- 72495
- Report Number(s):
- CONF-941144--; ISBN 1-55899-265-0
- Country of Publication:
- United States
- Language:
- English
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