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ArticleName Metallothermal synthesis of the Laves phase TaCr2 from oxide raw materials
DOI 10.17580/tsm.2020.11.07
ArticleAuthor Yudin S. N., Kasimtsev A. V., Volodko S. S., Guryanov A. M.

Metsintez Ltd., Tula, Russia:

S. N. Yudin, Head of the Technology Bureau, Сandidate of Technical Sciences, e-mail:
A. V. Kasimtsev, Director, Doctor of Technical Sciences, e-mail:


Tula State University, Tula, Russia:
S. S. Volodko, Postgraduate Student, Chair for Physics of Metals and Materials Science, e-mail:
A. M. Guryanov, Undergraduate Student, Chair for Physics of Metals and Materials Science, e-mail:


The refractory Laves phase TaCr2 of two compositions (series) was synthesized by the metallothermal (hydride-calcium) method from oxide raw materials (Cr2O3 + Ta2O5). The synthesis temperature was 1200 oC, while the excess of the reducing agent CaH2 was varied relative to the theoretically required for the complete reduction of oxides. It is shown that regardless of the excess of the reducing agent or in its complete absence, the resulting  powders have the required chemical composition (composition 1: calculated Cr content — 37.38% (wt.), actual — 37.50±0.85% (wt.); composition 2: calculated Cr content — 35.30% (wt.), actual — 35.38±0.31% (wt.)). No significant losses of Cr and Ta were observed during the synthesis of the Laves phase under the conditions of hydride-calcium reduction of Cr2O3 and Ta2O5. All prepared powders contained ~ 0.25% (wt.) oxygen and 0.025% (wt.) calcium. This is a good result for experimental batches first obtained by this method. Powders of the first series (composition 1), regardless of the excess of CaH2, contained no less than 85% (wt.) of the TaCr2 phase of the С15 type and ~ 10% (wt.) of the Cr(Ta) solid solution. However, when the excess of the reducing agent was >50 wt%, a high-temperature modification of the TaCr2 phase with a C14-type hexagonal lattice came in sight. The same picture was observed in the second series of experiments (composition 2). In all cases, the amount of the C14 type TaCr2 phase did not exceed 5% (wt.). Powders of composition 2 contained no less than 90% (wt.) of the C15 type TaCr2 phase or 95% (wt.), if there were two modifications C15 + C14. Depending on the excess of the CaH2 reductant, the alloys contained small amounts of Cr(Ta) or Ta2H hydride. In both series, the powder particles had a finely dispersed spongy structure; large particles of regular shape were present in an insignificant amount.

This work was carried out with financial support of the government of the Tula region (grant for work in the field of science and technology No. DS / 161 dated October 29, 2020).

keywords Metallothermy, hydride-calcium method, synthesis, TaCr2, chemical composition, phase composition, properties

1. Bei H., Pharr G. M., George E. P. A review of directionally solidified intermetallic composites for high-temperature structural applications. Journal of Materials Science. 2004. Vol. 39. pp. 3975–3984.
2. Anton D. L., Shah D. M., Duhl D. N., Giamei A. F. Selecting hightemperature structural intermetallic compounds: the engineering approach. JOM. 1989. Vol. 41, No. 9. pp. 12–16.
3. Duquette D. J., Stoloff N. S. Aerospace applications of intermetallics. Key Engineering Materials. 1992. Vol. 77–78. pp. 289–304.
4. Liu C. T. Recent advances in ordered intermetallics. Mat. Res. Soc. Symp. Proc. 1993. Vol. 288. pp. 3–19.
5. Meier G. H., Pettit F. S. High temperature oxidation and corrosion of intermetallic compounds. Materials Science and Technology. 1992. Vol. 8, No. 4. pp. 331–338.
6. Intermetallic compounds. Structural applications of intermetallic compounds. ed. Westbrook J. H., Fleischer R. L. New York : John Wiley & Sons, 2000. Vol. 3. 346 p.
7. Li C., Hoe J. L., Wu P. Empirical correlation between melting temperature and cohesive energy of binary Laves phases. Journal of Physics and Chemistry of Solids. 2003. Vol. 64. pp. 201–212.
8. Asano S., Ishida S. Magnetism and crystal structure of Laves phase compounds. J. Phys. F: Met. Phys. 1988. Vol. 18. pp. 501–515.
9. Livingston J. D. Laves-phase superalloys? Physica Status Solidi A. 1992. Vol. 131. pp. 415–423.
10. Liu C. T., Stringer J., Mundy J. N. et al. Ordered intermetallic alloys: an assessment. Intermetallics. 1997. Vol. 5. pp. 579–596.
11. Perepezko J. H., Nufies C. A., Yi S.-H., Thoma D. J. Phase stability in processing of high temperature intermetallic alloys. Mat. Res. Soc. Symp. Proc. 1997. Vol. 460. pp. 3–14.
12. Von Keitz A., Sauthoff G. Laves phases for high temperatures — Part II: Stability and mechanical properties. Intermetallics. 2002. Vol. 10. pp. 497–510.
13. Bhowmik A., Jones C. N., Edmonds I. M., Stone H. J. Effect of Mo, Al and Si on the microstructure and mechanical properties of Cr – Cr2Ta based alloys. Journal of Alloys and Compounds. 2012. Vol. 530. pp. 169–177.
14. He Y. H., Liaw P. K., Lu Y. et al. Effects of processing on the microstructure and mechanical behavior of binary Cr – Ta alloys. Materials Science and Engineering A. 2002. Vol. A329–331. pp. 696–702.
15. Xue Y., Li S., Wu Y. et al. Strengthening and toughening effects in laves phase Cr2Ta/Cr in-situ composites by Si additions. Vacuum. 2020. Vol. 174. pp. 109202.
16. Portnoi V. K., Leonov A. V., Filippova S. E. et al. Mechanochemical synthesis of chromium-based alloys. Inorganic Materials. 2016. Vol. 52, No. 9. pp. 895–901.
17. Hong S., Fu C. L., Yoo M. H. Elastic properties and stacking fault energies of Cr2Ta. Intermetallics. 1999. Vol. 7. pp. 1169–1172.
18. Bhowmik A., Stone H. J. Microstructure and mechanical properties of two-phase Cr – Cr2Ta alloys. Metallurgical and Materials Transactions A. 2012. Vol. 43A, No. 9. pp. 3283–3292.
19. Dupin N., Ansara L. Thermodynamic assessment of the Cr – Ta system. Journal of Phase Equilibria. 1993. Vol. 14, No. 4. pp. 451–546.
20. Jiang Y., Zomorodpoosh S., Roslyakova I., Zhang L. Thermodynamic re-assessment of the binary Cr – Ta system down to 0 K. International Journal of Materials Research. 2019. Vol. 110, No. 9. pp. 797–807.
21. Venkatraman M., Neumann J. P. The Cr – Ta (chromium-tantalum) system. Bulletin of Alloy Phase Diagrams. 1987. Vol. 8, No. 2. pp. 112–116.
22. Dorcheh Ali S., Galetz M. C. Challenges in developing oxidation-resistant chromium based alloys for applications above 900 oC. JOM. 2016. Vol. 68, No. 11. pp. 2793–2802.
23. Jönsson B., Westerlund A. Oxidation comparison of alumina-forming and chromia-forming commercial alloys at 1100 and 1200 oC. Oxidation of Metals. 2017. Vol. 88. pp. 315–326.
24. Brady M. P., Tortorelli P. F., Walker L. R. Correlation of alloy microstructure with oxidation behavior in chromia-forming intermetallic-reinforced Cr alloys. Materials at High Temperatures. 2000. Vol. 17, No. 2. pp. 235– 241.
25. Brady M. P., Zhu J. H., Liu C. T. et al. Oxidation resistance and mechanical properties of Laves phase reinforced Cr in-situ composites. Intermetallics. 2000. Vol. 8. pp. 1111–1118.
26. Meerson G. A., Kolchin O. P. On the mechanism of reduction of zirconium and titanium oxides with calcium hydride. Atomnaya energiya. 1957. Vol. 2, Iss. 3. pp. 253–259.
27. Kubaschewski O., Dench W. A. The dissociation pressures in the zirconium-oxygen system at 1000 oC. Journal of the Institute of Metals. 1955–56. Vol. 84. pp. 440–444.
28. Kubaschewski O., Dench W. A. the free-energy diagram of the system titanium-oxygen. Journal of the Institute of Metals. 1953–54. Vol. 82. pp. 87–91.
29. GOST 2912–79. Technical chromium oxide. Specifications. Introduced: 01.01.1980.
30. Specification 1764-348-00545484–95. Tantalum pentoxide (pure).
31. Specification 14-1-1737–76. Calcium hydride.
32. Shelekhov E. V., Sviridova T. A. Programs for X-ray analysis of polycrystals. Metal Science and Heat Treatment. 2000. Vol. 42, No. 8. pp. 309–313.

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