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Metallurgical and Materials Transactions A

, Volume 35, Issue 6, pp 1869–1879 | Cite as

Microstructural evolution in laser-deposited multilayer Ti-6Al-4V builds: Part II. Thermal modeling

  • S. M. Kelly
  • S. L. Kampe
Article

Abstract

The thermal history developed in laser metal deposition (LMD) processes has been shown to be quite complex and results in the evolution of an equally complex microstructure. A companion article (Part I. Microstructural Characterization) discussed the LMD of Ti-6Al-4V, where the resultant microstructure consists of a periodic, scale-graded layer of basketweave Widmanstätten alpha and a banding that consists of colony Widmanstätten alpha. In order to understand the microstructural evolution in Ti-6Al-4V, a numerical thermal model based on the implicit finite-difference technique was developed to model LMD processes. The effect of different laser-scan velocities on the characteristics of the thermal history was investigated using an eight-layer single-line build. As the laser-scan speed decreases and the position within a layer increases, the peak temperature increases. The heating rate and the peak thermal gradient within a deposited layer were shown to follow the same trend as the peak temperature after two layers were deposited on top of the substrate. In general, the laser-scan speed or z-position within a layer did not have a significant effect on the cooling rate. The cooling rate in a newly deposited layer decreases as the number of layer additions increases. Given the predicted temperature vs time profile from the thermal model, the evolution of phase transformations occurring in the deposit is mapped as each layer is deposited. As a result of the thermal cycling imposed by the periodic deposition of material, a characteristic layer, consisting of two regions heated above and below the beta transus, forms in layer n due to the deposition of layer n+1.

Keywords

Cool Rate Material Transaction Thermal Model Layer Deposition Characteristic Layer 
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.

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References

  1. 1.
    S.M. Kelly and S.L. Kampe: Metall. Mater. Trans. A, 2004, vol. 35A, pp. 1861–67.Google Scholar
  2. 2.
    M.L. Griffith, M.T. Ensz, J.D. Puskar, C.V. Robino, J.A. Brooks, J.A. Philliber, J.E. Smugeresky, and W.H. Hofmeister: in Solid Freeform and Additive Fabrication—2000, S.C. Danforth, D. Dimos, and F.B. Prinz, eds., Materials Research Society, Warrendale, PA, 2000, vol. 625, pp. 9–20.Google Scholar
  3. 3.
    M.L. Griffith, E. Schlienger, L.D. Harwell, M.S. Oliver, M.D. Baldwin, M.T. Ensz, M. Essien, J. Brooks, C.V. Robino, J.E. Smugeresky, W.H. Hofmeister, M.J. Wert, and D.V. Nelson: Mater. Design, 1999, vol. 20, pp. 107–13.CrossRefGoogle Scholar
  4. 4.
    L. Costa, T. Reti, A.M. Deus, and R. Vilar: Proc. 2002 Int. Conf. on Metal Powder Deposition for Rapid Manufacturing, D.M. Keicher, J.W. Sears, and J.E. Smugeresky, eds., Metal Powder Industries Federation, Princeton, NJ, 2002, pp. 172–79.Google Scholar
  5. 5.
    W.H. Hofmeister, M.L. Griffith, M.T. Ensz, and J.E. Smugeresky: JOM, 2001, vol. 53 (9), pp. 30–34.Google Scholar
  6. 6.
    W.H. Hofmeister, M.J. Wert, J.E. Smugeresky, J.A. Philliber, M.L. Griffith, and M.T. Ensz: JOM, 1999, vol. 51 (7) (http://www.tms.org/pubs/journals/JOM/9907/Hofmeister/Hofmeister-9907.html).Google Scholar
  7. 7.
    A. Vasinota, J. Beuth, and M.L. Griffith: in Solid Freeform Fabrication Proc., D. Bourell, J. Beaman, R. Crawford, H. Marcus, and J. Barlow, eds., University of Texas, Austin, TX, 1999, pp. 383–91.Google Scholar
  8. 8.
    P.A. Kobryn and S.L. Semiatin: in Solid Freeform Fabrication Proc., D. Bourell, J. Beaman, R. Crawford, H. Marcus, and J. Barlow, eds., University of Texas, Austin, TX, 2000, pp. 58–65.Google Scholar
  9. 9.
    P.A. Kobryn and S.L. Semiatin: JOM, 2001, vol. 53 (9), pp. 40–42.Google Scholar
  10. 10.
    M.N. Özisik: Finite Difference Methods in Heat Transfer, CRC, Ann Arbor, MI, 1997.Google Scholar
  11. 11.
    S. Wolfram: Mathematica, 1998–2002.Google Scholar
  12. 12.
    S.M. Kelly: Master’s Thesis, Virginia Tech, Blacksburg, VA (http://scholar.lib.vt.edu/theses/available/etd-05222002-223436/), 2002.Google Scholar
  13. 13.
    K.C. Mills: Recommended Values of Thermophysical Properties for Selected Commercial Alloys, Woodhead, Cambridge, United Kingdom, 2002.Google Scholar
  14. 14.
    F.G. Arcella and F.H. Froes: JOM, 2000, vol. 52 (5), pp. 28–30.Google Scholar
  15. 15.
    T.J. Wieting and J.T. Schriempf: J. Appl. Phys., 1976, vol. 47, pp. 4009–11.CrossRefGoogle Scholar
  16. 16.
    C. Hu and T.N. Baker: J. Mater. Processing Technol., 1999, vol. 94, pp. 116–22.CrossRefGoogle Scholar
  17. 17.
    V.M. Majdic and G. Ziegler: Z. Metallk., 1973, vol. 64, pp. 751–58.Google Scholar
  18. 18.
    T. Ahmed and H.J. Rack: Mater. Sci. Eng. A, 1998, vol. 243, pp. 206–11.CrossRefGoogle Scholar
  19. 19.
    T. DebRoy and S.A. David: Rev. Modern Phys., 1995, vol. 67, pp. 85–112.CrossRefGoogle Scholar
  20. 20.
    K. Mundra, T. DebRoy, S.S. Babu, and S.A. David: Welding J., 1997, vol. 76, pp. 163s-171s.Google Scholar
  21. 21.
    B.A.B. Anderrson: J. Eng. Mater. Technol., 1978, vol. 100, pp. 356–62.Google Scholar
  22. 22.
    J. Goldak, A. Chakravarti, and M. Bibby: Metall. Trans. B, 1984, vol. 15B, pp. 299–305.Google Scholar
  23. 23.
    I. Katzarov, S. Malinov, and W. Sha: Metall. Mater. Trans. A, 2002, vol. 33A, pp. 1027–40.CrossRefGoogle Scholar
  24. 24.
    F.J. Gil, J.M. Manero, and J.A. Planell: in Titanium ’95: Proc. 8th World Conf. on Titanium. H.M. Flower, ed., IOM, London, 1996, vol. 3, pp. 2454–61.Google Scholar
  25. 25.
    F.X. Gil Mur, D. Rodriguez, and J.A. Planell: J. Alloys Compounds, 1996, vol. 234, pp. 287–89.CrossRefGoogle Scholar
  26. 26.
    J.C. Chesnutt, C.G. Rhodes, and J.C. Williams: in Titanium and Titanium Alloys, M.J. Donachie, ed., ASM, Materials Park, OH, 1982, pp. 100–39.Google Scholar
  27. 27.
    O.M. Ivasishin: Proc. 6th World Conf. on Titanium, G. Beranger, ed., Les Editions de Physique, Les Ulis Cedex, France, 1989, pp. 1535–39.Google Scholar
  28. 28.
    G. Lütjering, J. Albrecht, and O.M. Ivasishin: in Microstructure/Property Relationships of Titanium Alloys, J.A. Hall, ed., TMS, Warrendale, PA, 1994, pp. 65–75.Google Scholar
  29. 29.
    O.M. Ivasishin and G. Lütjering: Mater. Sci. Eng. A, 1993, vol. 168, pp. 23–28.CrossRefGoogle Scholar
  30. 30.
    W. Szkliniarz and G. Smolka: J. Mater. Processing Technol., 1995, vol. 53, pp. 413–22.CrossRefGoogle Scholar
  31. 31.
    P.S. Goodwin, C. Mitchell, J. Liang, J. Mei, and X. Wu: Proc. 2002 Int. Conf. on Metal Powder Deposition for Rapid Manufacturing, D.M. Keicher, J.W. Sears, and J.E. Smugeresky, eds., Metal Powder Industries Federation, Princeton, NJ, 2002, pp. 87–95.Google Scholar
  32. 32.
    P.A. Kobryn, E.H. Moore, and S.L. Semiatin: Scripta Mater., 2000, vol. 43, pp. 299–305.CrossRefGoogle Scholar
  33. 33.
    S.M. Kelly: Oak Ridge National Laboratory, Oak Ridge, TN, unpublished research, 2004.Google Scholar

Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2004

Authors and Affiliations

  • S. M. Kelly
    • 1
  • S. L. Kampe
    • 1
  1. 1.the Materials Science and Engineering DepartmentVirginia TechBlacksburg

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