On the microstructure and crystallography of directionally solidified MoSi{sub 2}-Mo{sub 5}Si{sub 3} eutectics
- Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Materials Science and Engineering
- Univ. of Missouri, Rolla, MO (United States). Dept. of Metallurgical Engineering
Directionally solidified MoSi{sub 2}-Mo{sub 5}Si{sub 3} eutectic rods were produced by the Czochralski method. A script lamellar microstructure was produced and an inverse square root dependence upon the pull rate (39--210 mm/h) was observed for the lamellar spacing. The eutectic rods were textured with [001] of Mo{sub 5}Si{sub 3} and <110> of MoSi{sub 2} parallel to the rod axis and an orientation relationship consisting of [110]MoSi{sub 2}{vert_bar}{vert_bar}[110]Mo{sub 5}Si{sub 3} and (1{bar 1}0)MoSi{sub 2}{vert_bar}{vert_bar}(002)Mo{sub 5}Si{sub 3} was present in all of the samples. The eutectic grows with a lamellar plate morphology inclined at 15{degree} relative to the rod axis and four growth variants are possible. A script lamellar microstructure, as viewed in the transverse plane, was produced by periodic branching of the Mo{sub 5}Si{sub 3} lamellae and this branching was not associated with any change in crystallography. Addition of 0.35 at.% erbium produced a more fibrous microstructure and an erbium-rich compound, Er{sub 2}Mo{sub 3}Si{sub 4} with space group 2{sub 1}/c, formed congruently with the Mo{sub 5}Si{sub 3}-MoSi{sub 2} during solidification. A ledge-terrace growth mechanism was proposed to explain the observed microstructures.
- OSTI ID:
- 31736
- Journal Information:
- Acta Metallurgica et Materialia, Journal Name: Acta Metallurgica et Materialia Journal Issue: 3 Vol. 43; ISSN 0956-7151; ISSN AMATEB
- Country of Publication:
- United States
- Language:
- English
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