Advertisement

Metallurgical and Materials Transactions A

, Volume 40, Issue 4, pp 838–855 | Cite as

Nb-Base FS-85 Alloy as a Candidate Structural Material for Space Reactor Applications: Effects of Thermal Aging

  • Keith J. LeonardEmail author
  • Jeremy T. Busby
  • David T. Hoelzer
  • Steven J. Zinkle
Article

Abstract

The proposed uses of fission reactors for manned or deep space missions have typically relied on the potential use of refractory metal alloys as structural materials. Throughout the history of these programs, a leading candidate has been Nb-1Zr, due to its good fabrication and welding characteristics. However, the less-than-optimal creep resistance of this alloy has encouraged interest in the more complex FS-85 (Nb-28Ta-10W-1Zr) alloy. Despite this interest, only a relatively small database exists for the properties of FS-85. Database gaps include the potential microstructural instabilities that can lead to mechanical property degradation. In this work, changes in the microstructure and mechanical properties of FS-85 were investigated following 1100 hours of thermal aging at 1098, 1248, and 1398 K. The changes in electrical resistivity, hardness, and tensile properties between the as-annealed and aged materials are compared. Evaluation of the microstructural changes was performed through optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The development of intragranular and grain-boundary precipitation of Zr-rich compounds as a function of aging temperature was followed. Brittle tensile behavior was measured in the material aged at 1248 K, while ductile behavior occurred in samples aged above and below this temperature. The effect of temperature on the under- and overaging of the grain-boundary particles is believed to have contributed to the mechanical property behavior of the aged materials.

Keywords

Electrical Resistivity Electrical Discharge Machine Aging Temperature Thermal Aging Dynamic Strain Aging 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

The authors express their gratitude to J. Hack, R. Baranwal, T.M. Angeliu, and Y. Ballout of the Naval Reactors Prime Contractor Team, for many helpful technical discussions and for their guidance. The authors also thank Marie Williams, Mike Pershing, and Cliff Davison, for their help in the acid cleaning and annealing of the specimens prior to thermal aging; Jeffrey McNabb and Bob Sitterson, for welding and leak testing the alloy 600 aging cans; Brian Sparks and David Harper, for thermal aging the encapsulated materials; and Kathy Thomas and Jackie Mayotte, for their help in preparing samples for microscopy. The authors also thank Louis K. Mansur and Chad E. Duty for their helpful discussions and their review of this article. This work was performed under the sponsorship of the NASA Project Prometheus and was directed by the U.S. Department of Energy/National Nuclear Security Administration (DOE/NNSA) Naval Reactors. Opinions and conclusions drawn by the authors are not endorsed by the DOE/NNSA Naval Reactors. Research at the Oak Ridge National Laboratory (ORNL) SHaRE User Center was sponsored by the Division of Materials Sciences and Engineering, DOE. The ORNL is managed for the DOE by UT-Battelle, LLC, under Contract No. DE-AC-05-00OR22725.

References

  1. 1.
    L.J. Pionke and J.W. Davis: Technical Assessment of Niobium Alloys Data Base for Fusion Reactor Applications, McDonnell Douglas Report No. C00-4247-2, 1979.Google Scholar
  2. 2.
    J.T. Busby and K.J. Leonard: JOM, 2007, vol. 59 (4), pp. 20–26.CrossRefGoogle Scholar
  3. 3.
    C.C. Wojcik: Mater. Res. Soc. Symp. Proc., 1994, vol. 322, pp. 519–30.Google Scholar
  4. 4.
    K.J. Leonard, C.E. Duty, S.J. Zinkle, R.F. Luther, R.E. Gold, and R.W. Buckman: Proc. Space Nuclear Conf., San Diego, CA, 2005, pp. 286–93.Google Scholar
  5. 5.
    J.A. Horak and L.K. Egner: Creep Properties of Nb-1Zr and Nb-1Zr-0.1C, ORNL-6809, Oak Ridge National Laboratory, Oak Ridge, TN, 1994.Google Scholar
  6. 6.
    Technical Publication on Nb and Nb-Alloy Products, Wah Chang, Albany, OR, 2006.Google Scholar
  7. 7.
    S.J. Zinkle: Fusion Materials Semi-Annual Report, DOE/ER-0313/27, 1999, pp. 175–82.Google Scholar
  8. 8.
    D.J. Senor and J.A. Horak: Material Property Correlations for W-25Re, Mo-50Re and ASTAR-811C, unpublished report, 1989, pp. 1–207.Google Scholar
  9. 9.
    E.J. Delgrosso, C.E. Carlson, and J.J. Kaminsky: J. Less Common Met., 1967, vol. 12, pp. 173–201.CrossRefGoogle Scholar
  10. 10.
    Materials Handbook for SP-100, Document No. 23A3181, rev. 0, 1988.Google Scholar
  11. 11.
    R.H. Titran and M. Uz: Effects of Thermomechanical Processing on the Microstructure and Mechanical Properties of Nb-1Zr-C Alloys, NASA Technical Memorandum 107207, 1993.Google Scholar
  12. 12.
    R.L. Stephenson: J. Less Common Met., 1968, vol. 15 (3), pp. 395–402.CrossRefGoogle Scholar
  13. 13.
    D.M. Farkas and A.K. Mukherjee: J. Mater. Res., 1996, vol. 11 (9), pp. 2198–2205.CrossRefADSGoogle Scholar
  14. 14.
    G.G. Lessmann: The Weldability of Refractory Metal Alloys, WANL-PR-P-013 Report, Westinghouse Astronuclear Laboratory, Pittsburgh, PA, 1969.Google Scholar
  15. 15.
    R.L. Stephenson: Creep-Rupture Properties of FS-85 Alloy and Their Response to Heat Treatment, ORNL-TM-1456, Oak Ridge National Laboratory, Oak Ridge, TN, 1966.Google Scholar
  16. 16.
    R.H. Titran and R.W. Hall: High-Temperature Creep Behavior of a Columbium Alloy, FS-85, NASA Technical Note D-2885, 1965.Google Scholar
  17. 17.
    R.H. Titran and R.W. Hall: Ultrahigh-Vacuum Creep Behavior of Columbium and Tantalum Alloys at 2000 and 2200 °F for Times Greater Than 1000 Hours, NASA Technical Note D-3222, 1965.Google Scholar
  18. 18.
    G.G. Lessmann and R.E. Gold: Thermal Stability of Refractory Metal Alloys, NASA-SP-245 Report, Westinghouse Astronuclear Laboratory, Pittsburgh, PA, 1970.Google Scholar
  19. 19.
    T.A. Moss: Nuclear Applications, 1967, vol. 3, pp. 71–81.Google Scholar
  20. 20.
    R.G. Frank: AIME Symposium on Metallurgy and Technology of Refractory Metal Alloys, TMS-AIME, Plenum Press, New York, NY, 1968, p. 325.Google Scholar
  21. 21.
    K.J. Leonard, J.T. Busby, and S.J. Zinkle: J. Nucl. Mater., 2007, vol. 366, pp. 336–52.CrossRefADSGoogle Scholar
  22. 22.
    ASTM Designation B 193-87, ASTM Standards Online, ASTM, West Conshohocken, PA, 1992.Google Scholar
  23. 23.
    A. Buch: Pure Metal Properties: A Scientific Technical Handbook, ASM International and Freund Publishing House, Ltd., Materials Park, OH, 1999.Google Scholar
  24. 24.
    ASTM Standard E8-04, ASTM Standards Online, ASTM, West Conshohocken, PA, 2001.Google Scholar
  25. 25.
    Aerospace Structural Metals Handbook, 37th ed., W.F. Grown and S.J. Setlak, eds., CIMDAS/USAF CRDA Handbooks Operation, Purdue University, West Lafayette, IN, vol. 6.Google Scholar
  26. 26.
    R.L. Stephenson: J. Less Common Met., 1968, vol. 15, pp. 403–14.CrossRefGoogle Scholar
  27. 27.
    Binary Alloy Phase Diagrams, vol. 2, T.B. Massalski, ed., ASM INTERNATIONAL, Materials Park, OH, 1986.Google Scholar
  28. 28.
    D.B. Williams and C.B. Carter: Transmission Electron Microscopy, Plenum Press, New York, NY, 1996.Google Scholar
  29. 29.
    F.-G. Wei, T. Hara, and K. Tsuzaki: Philos. Mag., 2004, vol. 84 (17), pp. 1735–51.CrossRefADSGoogle Scholar
  30. 30.
    (a) D.T. Hoelzer, A.F. Rowcliffe, and M. Li: Fusion Materials Semi-Annual Report, DOE/ER-0313/38, 2005, pp. 2–11. (b) D.T. Hoelzer and S.J. Zinkle: Fusion Materials Semi-Annual Report, DOE/ER-0313/29, 2000, pp. 19–25.Google Scholar
  31. 31.
    K. Schroeder: CRC Handbook of Electrical Resistivities of Binary Metallic Alloys, CRC Press, Boca Raton, FL, 1983.Google Scholar
  32. 32.
    (a) M. Li, D.T. Hoelzer, and S.J. Zinkle: Fusion Materials Semi-Annual Report, DOE/ER-0313/34, 2003, pp. 2–5. (b) S.J. Zinkle, A.N. Gubbi, and W.S. Eatherly: Fusion Materials Semi-Annual Report, DOE/ER-0313/21, 1996, pp. 15–19.Google Scholar
  33. 33.
    G.G. Lessmann: Determination of the Weldability and Elevated Temperature Stability of Refractory Metal Alloys, WANL-PR(p)-013 Report, Westinghouse Astronuclear Laboratory, Pittsburgh, PA, 1969.Google Scholar
  34. 34.
    J.B. Lambert and J.J. Rausch: Metals Handbook, 10th ed., ASM INTERNATIONAL, Materials Park, OH, 1990, vol. 2.Google Scholar
  35. 35.
    J.R. Stephens: Metallography, 1977, vol. 10, pp. 1–25.CrossRefGoogle Scholar

Copyright information

© The Minerals, Metals & Materials Society and ASM International 2009

Authors and Affiliations

  • Keith J. Leonard
    • 1
    Email author
  • Jeremy T. Busby
    • 1
  • David T. Hoelzer
    • 1
  • Steven J. Zinkle
    • 1
  1. 1.Oak Ridge National LaboratoryMaterials Science and Technology DivisionOak RidgeUSA

Personalised recommendations