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Analyses of The Eutectoid Phase Transformation in Complex Ds Nb-Silicide In-Situ Composites

Published online by Cambridge University Press:  02 July 2020

S.D. Sitzman  and
B.P. Bewlay
S.D. Sitzman
Affiliation:
TiTech International, Inc., Pomona, CA91768
B.P. Bewlay
Affiliation:
General Electric Corporate Research and Development, Schenectady, New York, 12301
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Abstract

In-situ composites based on (Nb) and Nb silicides, such as Nb5Si3 (tI32 crystal structure) and Nb3Si (tP32 crystal structure), are being investigated for revolutionary high-temperature structural applications [1,2]. The use of Hf and Ti alloying additions to these silicides has also been examined; in these systems Nb5Si3 has also been observed with the hP16 structure. The present paper describes EBSD analyses of a directionally solidified (DS) Nb-silicide based composite that experienced a eutectoid transformation. The composites were directionally solidified using the Czochralski method as described previously [1]. The composites were creep tested at 1200°C for 24 hours. Microstructure and microtexture characterization were performed using scanning electron microscopy, and electron backscatter diffraction pattern analysis (EBSD).

The microstructure of a composite directionally solidified from a Nb-12.5Hf-33Ti-16Si alloy is shown in Figure 1. in the as-DS condition the microstructure consisted of primary (Nb)3Si dendrites and coarse (Nb)3Si-(Nb) two-phase cells.

Type
Metals and Alloys
Information
Microscopy and Microanalysis , Volume 7 , Issue S2: Proceedings: Microscopy & Microanalysis 2001, Microscopy Society of America 59th Annual Meeting, Microbeam Analysis Society 35th Annual Meeting, Long Beach, California August 5-9, 2001 , August 2001 , pp. 1244 - 1245
Copyright
Copyright © Microscopy Society of America 2001

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References

References:

1.Bewlay, B.P., Jackson, M.R., and P.R. Subramanian, , JOM, (1999) Vol 51(4) (1999), pp. 32–36.CrossRefGoogle Scholar
2.Mendiratta, M.G. and Dimiduk, D.M., Metall. Trans. A 24A (1993), pp. 501–504.CrossRefGoogle Scholar