Metallurgical and Materials Transactions B

, Volume 32, Issue 6, pp 1041–1052

Cathodic deoxygenation of the alpha case on titanium and alloys in molten calcium chloride

  • George Zheng Chen
  • Derek J. Fray
  • Tom W. Farthing
Article

Abstract

The oxygen-enriched alpha case on titanium and alloys was successfully deoxygenated to satisfactory levels by electrolysis in molten CaCl2, in which the cathode was made from the metal to be refined. The oxygen distribution in the metal before and after electrolysis was characterized by microhardness tests, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). The electrolysis has been carried out at voltages sufficiently below that for the decomposition of CaCl2, and the results obtained suggest that the alpha case deoxygenation follows a simple oxygen ionization mechanism in which the oxygen in the metal is simply ionized at the cathode/electrolyte interface, dissolves in the molten salt, and then discharges at the anode. It is shown that by applying the electrochemical method, the alpha cases on both commercially pure titanium (CP Ti) and the Ti-6Al-4V alloy can be effectively deoxygenated. In particular, due to the removal of oxygen, the original alpha case (single phase) on the Ti-6Al-4V alloy has been converted back to the two-phase microstructure.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Titanium Science and Technology, R.I. Jaffee and H.M. Burte, eds., Plenum Press, New York, NY, 1973.Google Scholar
  2. 2.
    A.D. McQuillan and M.K. McQuillan: Titanium, Butterworths Scientific Publications, London, 1956.Google Scholar
  3. 3.
    CRC Hand Book of Chemistry and Physics, 77th ed., D.R. Lide, ed., CRC Press, Boca Raton, FL, 1996.Google Scholar
  4. 4.
    Handbook of Extractive Metallurgy, F. Habashi, ed., Wiley-VCH, Weinheim, 1997, vol. II, pp. 1129–80.Google Scholar
  5. 5.
    G.Z. Chen, D.J. Fray, and T.W. Farthing: Nature, 2000, vol. 407, pp. 361–64.CrossRefGoogle Scholar
  6. 6.
    HSC Chemistry for Windows, Outokumpu Research, Pori, Finland, 1994.Google Scholar
  7. 7.
    Binary Alloy Phase Diagrams, T.B. Massalski, H. Okamoto, P.R. Subramanian, and L. Kacprzak, eds., 2nd ed., ASM INTERNATIONAL, Materials Park, OH, 1990, vol. 3, pp. 2924–27.Google Scholar
  8. 8.
    R.W. Evans, R.J. Hull, and B. Wilshire: J. Mater. Proc. Technol., 1996, vol. 56, pp. 492–501.CrossRefGoogle Scholar
  9. 9.
    U.S. Patent 5,022,935, RMI Titanium, Niles, OH, 1991.Google Scholar
  10. 10.
    T.H. Okabe, T. Oishi, and K. Ono: J. Alloys Compounds, 1992, vol. 184, pp. 43–56.CrossRefGoogle Scholar
  11. 11.
    T.H. Okabe, M. Nakamura, T. Oishi, and K. Ono: Metall. Trans. B, 1993, vol. 24, pp. 449–55.Google Scholar
  12. 12.
    T.H. Okabe, T.N. Deura, T. Oishi, K. Ono, and D.R. Sadoway: J. Alloys Compounds, 1996, vol. 237, pp. 150–54.CrossRefGoogle Scholar
  13. 13.
    K. Hirota, T.H. Okabe, F. Saito, Y. Waseda, and K.T. Jacob: J. Alloys Compounds, 1999, vol. 282, pp. 101–08.CrossRefGoogle Scholar
  14. 14.
    R.G. Ward and T.P. Hoar: J. Inst. Met., 1961–62, vol. 90, pp. 6–12.Google Scholar
  15. 15.
    S. Boghosian, A. Godo, H. Mediaas, W. Ravlo, and T. Ostvold: Acta Chem. Scand. 1991, vol. 45, pp. 145–57.CrossRefGoogle Scholar
  16. 16.
    E.M. Levin and H.F. McMurdie: Phase Diagrams for Ceramists, 1975 Suppl., American Ceramic Society, Columbus, OH, 1975, pp. 394.Google Scholar
  17. 17.
    G.Z. Chen and D.J. Fray: J. Appl. Electrochem., 2001, vol. 31, pp. 155–64.CrossRefGoogle Scholar
  18. 18.
    Binary Alloy Phase Diagrams, T.B. Massalski, ed., ASM INTERNATIONAL, The Materials Information Society, Materials Park, OH, 1990 Ca-Cu, vol. 1, p. 907; Cu-Ba, vol. 1, p. 573; and O-Cu, vol. 2, p. 1447.Google Scholar
  19. 19.
    A.E. Jenkins: J. Inst. Met., 1953–54, vol. 82, p. 213.Google Scholar
  20. 20.
    Z.M. Turovtseva and L.L. Kunin: Analysis of Gases in Metals, Consultants Bureau, New York, NY, 1961, (translation by J. Thompson).Google Scholar
  21. 21.
    Wilson and Wilson’s Comprehensive Analytical Chemistry, G. Svehla, ed., Elsevier, Oxford, United Kingdom, 1975, vol. 3.Google Scholar
  22. 22.
    P. Lacombe: in Titanium and Titanium Alloys—Scientific and Technological Aspects, J.C. Williams and A.F. Belov, eds., Plenum Press, New York, NY, 1982, vol. 2, p. 1045.Google Scholar
  23. 23.
    Materials Properties Handbook: Titanium Alloys, R. Boyer, G. Welsch, and E.W. Collings, eds., ASM INTERNATIONAL, Materials Park, OH, 1994, p. 149.Google Scholar
  24. 24.
    H. O’Neill: Hardness Measurement of Metals and Alloys, Chapman and Hall Ltd, London, 1967, p. 124.Google Scholar
  25. 25.
    S. Abkowitz, J.J. Burke, and R.H. Hiltz, Jr.: Titanium in Industry—Technology of Structural Titanium, D. Van Nostrand Company, Inc., London, 1995, pp. 40–42.Google Scholar
  26. 26.
    M.E. Sibert, Q.H. McKenna, M.A. Steinberg, and E. Wainer: J. Electrochem. Soc., 1955, vol. 102, p. 252.CrossRefGoogle Scholar

Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2001

Authors and Affiliations

  • George Zheng Chen
    • 1
  • Derek J. Fray
    • 1
  • Tom W. Farthing
    • 3
  1. 1.the Department of Materials Science and MetallurgyUniversity of CambridgeCambridgeUnited Kingdom
  2. 2.Timet UK Ltd.West MidlandUnited Kingdom
  3. 3.AlresfordEngland

Personalised recommendations