Advertisement

Evaluation of microstructure and phase relations in a powder processed Ti-44AI-12Nb alloy

  • 70 Accesses

  • 13 Citations

Abstract

Titanium aluminides based on the ordered face-centered tetragonal γTiAI phase possess attractive properties, such as low density, high melting point, good elevated temperature strength, modulus retention, and oxidation resistance, making these alloys potential high-temperature structural materials. These alloys can be processed by both ingot metallurgy and powder metallurgy routes. In the present study, three variations of the powder metallurgy route were studied to process a Ti-44Al-12Nb (at. %) alloy: (a) cold pressing followed by reaction sintering (CPprocess); (b) cold pressing, vacuum hot pressing, and then sintering (HP process); and (c) arc melting, hydride-dehydride process to make the alloy powder, cold isostatic pressing, and then sintering (AM process). Microstructural and phase relations were studied by x-ray diffraction (XRD) analysis, optical microscopy, scanning electron microscopy with an energy-dispersive spectrometer (SEM-EDS), and electron probe microanalysis (EPMA). The phases identified were Ti3AI and TiAl; an additional Nb2AI phase was observed in the HPsample. The microstructures of CPand HP processed samples are porous and chemically inhomogeneous whereas the AM processed sample revealed fine equiaxed microstructure. This refinement of the microstructure is attributed to the fine, homogeneous powder produced by the hydride-dehydride process and the high compaction pressures.

This is a preview of subscription content, log in to check access.

Access options

Buy single article

Instant unlimited access to the full article PDF.

US$ 39.95

Price includes VAT for USA

Subscribe to journal

Immediate online access to all issues from 2019. Subscription will auto renew annually.

US$ 408

This is the net price. Taxes to be calculated in checkout.

References

  1. 1.

    W.B. Pearson,A Handbook of Lattice Spacings and Structures of Metals and Alloys, Vol 2, Pergamon Press, 1967, p 126

  2. 2.

    J.R. Groza, S.H. Risbud, and K. Yamazaki,Proc. Plasma Synthesis and Processing of Materials, K. Upadhya, Ed., TMS, 1993, p 85–93

  3. 3.

    F.H. Froes,C. Suryanarayana, and D. Elizer,J. Mater Sci., Vol 27, 1992, p 5113–5140

  4. 4.

    D.P. Pope,Proc. High Temperature Aluminides and Intermetallics, S.H. Whang, C.T. Liu, D.R Pope, and J.O. Stiegler, Ed., TMS, 1992, p 51–61

  5. 5.

    Y Nishiyama, T. Miyashita, S. Isobe, and T. Noda,Proc. High Temperature Aluminides and Intermetallics, S.H. Whang, C.T. Liu, D.R Pope, and J.O. Stiegler, Ed., TMS, 1991, p 557–584

  6. 6.

    R.G. Rowe,Adv. Mater Proc, Vol 141 (No. 3), 1992, p 33

  7. 7.

    YW. Kim,J. Met., July 1989, p 24–30

  8. 8.

    T. Tsujimoto and K. Hashimoto,Proc. High Temperature Ordered Intermetallic Alloys III, Vol 133, C.T. Liu, A.I. Taub, N.S. Stoloff, and C.C. Koch, Ed., MRS, 1989, p 391–396

  9. 9.

    S.G. Kumar and R.G. Reddy,Proc. Extractive Metallurgy of Copper Nickel and Cobalt, R.G. Reddy and R.N. Weizenbach, Ed., TMS, 1993, p 1101–1123

  10. 10.

    J.H. Moll, C.F. Yolton, and B.J. McTiernan,Int. J. Powder Metall.,Vol 26 (No.2), 1990, p 149–155

  11. 11.

    R.E. Schafrik,Metall. Trans. B, Vol 7, 1976, p 713–716

  12. 12.

    G.-X. Wang and M. Dahms,Metall. Trans. A, Vol 24, 1993, p 1517–1526

  13. 13.

    F.H. Froes, D. Eylon, and C. Suryanarayana,JOM, Vol 42 (No. 3), 1990, p 26

  14. 14.

    S.G. Kumar and R.G. Reddy, unpublished research

  15. 15.

    R.G. Reddy and K.N. Hebbar,Proc. Electron Beam Melting and Refining—State of the Art 1991, R. Bakish, Ed., Bakish Materials Corporation, 1991, p 248–291

  16. 16.

    D.M. Kocherginsky and R.G. Reddy,Proc. Control of Interfaces in Metal and Ceramic Composites, R.Y Lin and S.G. Fishman, Ed., TMS, 1994, p71–79

  17. 17.

    S.G. Kumar, R.G. Reddy, and L. Brewer,J. Phase Equilibria, Vol. 15 (No. 3), June 1994, p. 279–284

  18. 18.

    U.R. Kattner, J.-C. Lin, and YA. Chang,Metall. Trans. A, Vol 23, 1992, p 2081

  19. 19.

    J.A. Graves, J.H. Perepezko, C.H. Ward, and F.H. Froes,Scr. Metall, Vo1 21, 1987, p 567–572

  20. 20.

    J.J. Milencia, C. McCullough, C.-G. Levi, and R. Mehrabian,Scr Metall., Vol 21, 1987, p 1341–1346

  21. 21.

    G.E. Fuchs and S.Z. Hayden,Matee Sci. Eng. A, Vol 152,1992, p 277–282

  22. 22.

    A. Kawabata, T. Tadano, and O. Izumi,Scr Metall., Vo1 22, 1988, p 1725–1730

  23. 23.

    R Prasad Rao and K. Tangri,Matee Sci. Eng. A, Vo1 132, 1991, p 49–59

  24. 24.

    C.R. Feng, D.J. Michel, and C.R. Crowe,Mater Sci. Eng. A, Vo1 145, 1991, p 257–264

  25. 25.

    S. Yamauchi and H. Shiraishi,Mater Sci. Eng. A, Vol 152,1992, p 283–287

  26. 26.

    FV Lenel,Powder Metallurgy: Principles and Applications, Metal Powder Industries Federation, 1980

  27. 27.

    J.H. Perepezko, YA. Chang, L.E. Seitzman, J.C. Lin, N.R. Bonda, T.J. Jewett, and J.C. Mishurda,Proc. High Temperature Aluminides and Intermetallics, S.H. Whang, C.T. Liu, D.R Pope, and J.O. Stiegler, Ed., TMS, 1991, p 19–47

  28. 28.

    C. Suryanarayana, G.-H. Chen, A. Freier, and F.H. Froes,Mater Sci. Eng. A, Vol 158, 1992, p 93–101

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Kumar, S.G., Reddy, R.G., Wu, J. et al. Evaluation of microstructure and phase relations in a powder processed Ti-44AI-12Nb alloy. JMEP 4, 63–69 (1995) doi:10.1007/BF02682707

Download citation

Keywords

  • microstructure
  • phase relations
  • powder metallurgy
  • titanium alloy