Journals →  Tsvetnye Metally →  2014 →  #8 →  Back

ArticleName Structural-phase state of Nb – Si eutectic alloys, doped by yttrium and scandium
ArticleAuthor Udoeva L. Yu., Chumarev V. M., Leontev L. I., Selmenskikh N. I.

Institute of Metallurgy of Ural Department of Russian Academy of Sciences, Ekaterinburg, Russia:

L. Yu. Udoeva, Senior Researcher, e-mail:
V. M. Chumarev, Chief Researcher
L. I. Leontev, Chief Researcher
N. I. Selmenskikh, Researcher


Influence of rare earth metals on structural-phase state of Nb – Si eutectic alloy was considered on example of yttrium and scandium. On the basis of phase diagrams and thermodynamic analysis of interactions in Nb – Si – Y and Nb – Si – Sc systems, there was carried out a theoretical estimation of dependences of the phase state of eutectic composites on the temperature and doping element content. For the purpose of experimental verification of calculated data, the model of Nb – 18.7 Si alloys (1.0–6.0% (at.) of yttrium and 0.9–2.6% (at.) of scandium) was obtained by vacuum-arc melting. In the researched samples, a phase composition and distribution of doping elements between structural components were determined with the help of X-ray diffraction, optical microscopy and electron probe microanalysis. There was found that phase formation of eutectic Y and Sc doped Nb – Si alloys basically corresponds to equilibrium principles and obtained thermodynamic models, which can be used for forecasting of phase composition of Nb – Si alloys. Scandium concentration from 0.9 to 2.6% (at.) does not affect the Nbss/silicides ratio in Nb – 18.7 Si eutectic alloy, while yttrium in the range of 1.0–6.0% (at.) increases the Nbss solid solution share twice. Yttrium and scandium significantly increase the dispersity of Nb – 18.7 Si alloy structure due to their surfactant properties and refine the Nb – Si alloys from oxygen impurities, forming refractory oxides Y2O3 and Sc2O3. Furthermore, these elements stabilize the high-temperature Nb3Si silicide within the range of test concentrations, hindering the eutectoid decomposition of Nb3Si → Nbss + α-Nb5Si3 at the temperature of 1770 oC.

keywords Eutectic alloys, Nb – Si alloy, doping, yttrium, scandium, thermodynamic modeling, phase composition, microstructure, eutectoid transformation

1. Petrushin N. V., Svetlov I. L., Ospennikova O. G. Liteynye zharoprochnye nikelevye splavy (Cast heat-resistance nickel alloys). Vse materialy. Entsiklopedicheskiy spravochnik = All the Materials. Encyclopaedic Reference Book. 2012. No. 5. pp. 15–19.
2. Bewlay B. P., Jackson M. R., Zhao J.-C., Subramanian P. R. A review of very-high-temperature Nb-silicide–based composites. Metallurgical and materials transactions A. 2003. Vol. 34A, No. 10. pp. 2043–2052.
3. Grashchenkov D. V., Shchetanov B. V., Efimochkin I. Yu. Razvitie poroshkovoy metallurgii zharoprochnykh materialov (Development of powder metallurgy of heat-resistance materials). Vse materialy. Entsiklopedicheskiy spravochnik = All the Materials. Encyclopaedic Reference Book. 2011. No. 5. pp. 13–26.
4. Jackson M. R., Bewlay B. P., Rowe R. G., Skelly D. W., Lipsitt H. A. High-temperature refractory metal-intermetallic composites. Journal of the Minerals, Metals and Materials Society. 1996. Vol. 48, No. 1. pp. 39–44.
5. Drawin S., Heilmaier M., Jehanno P. et al. The EU-funded “ULTMAT” project: Ultra high temperature materials for turbines. 25th International Congress of Aeronautical Sciences. 2006. Available at:
6. Svetlov I. L., Abuzin Yu. A., Babich B. N., Vlasenko S. Ya., Efimochkin I. Yu., Timofeeva O. B. Vysokotemperaturnye niobievye kompozity, uprochnennye silitsidami niobiya (High-temperature niobium composites, strengthened by niobium silicides). Funktsionalnye materialy = Functional Materials. 2007. Vol. 1, No. 2. pp. 48–53.
7. Stringer J. The reactive element effect in high-temperature corrosion. Material Science and Engineering. 1989. Vol. A120. pp. 129–137.
8. Roine A. Chemical reactions and Equilibrium software with extensive thermochemical database and flowsheet simulation. HSC 6.0 Chemistry : Outokumpu research Oy. Pori, 2006. 448 p.
9. Meschel S. V., Kleppa O. J. Standard enthalpies of formation of some 4d transition metal silicides by high temperature direct synthesis calorimetry. Journal of Alloys and Compounds. 1998. Vol. 274, Iss. 1/2. pp. 193–200.
10. Shukla A., Kang Y.-B., Pelton A. D. Thermodynamic assessment of the Ce – Si, Y – Si, Mg – Ce – Si and Mg – Y – Si systems. International Journal of Materials Research. 2009. Vol. 100, Iss. 2. pp. 208–217.
11. Topor L., Kleppa O. J. Standard enthalpy of formation of Sc5Si3. Metallurgical Transactions B. 1989. Vol. 20, Iss. 6. pp. 879–882.
12. Kubashevskiy O., Olkokk S. B. Metallurgicheskaya termokhimiya (Metallurgical thermochemistry). Moscow : Metallurgiya, 1982. 392 p.
13. Schlesinger M. E., Okamoto H., Gokhale A. B., Abbaschian R. The Niobium-Silicon System. Journal of Phase Equilibria. 1993. Vol. 14, No. 4. pp. 502–509.
14. Jiang W., Zhan Y., Li C. et al. Phase equilibria in Nb-Y-Si ternary system at 873 K. Journal of Rare Earths. 2012. Vol. 30, No. 9. pp. 934–940.
15. Kotur B. Ya. Vzaimodeystvie skandiya s niobiem i kremniem (ili germaniem) (Interaction of scandium with niobium and silicon (or germanim)). Doklady Akademii Nauk USSR. Seriya fiziko-matematicheskoy i tekhnicheskoy nauki = Reports of USSR Academy of Sciences. Series of physical-mathematical and technical science. 1986. No. 1. pp. 82–86.
16. Shiyu Q., Yafang H., Liquo S. Effect of alloying elements on phase stability in Nb – Si system intermetallics materials. Intermetallics. 2007. Vol. 15. pp. 810–813.

Language of full-text russian
Full content Buy