Metallurgical and Materials Transactions A

, Volume 42, Issue 12, pp 3729–3742 | Cite as

Effect of Composition and Deformation on Coarse-Grained Austenite Transformation in Nb-Mo Microalloyed Steels

  • N. Isasti
  • D. Jorge-Badiola
  • M. L. Taheri
  • B. López
  • P. Uranga
Symposium: Austenite Formation and Decomposition IV


Thermomechanical processing of microalloyed steels containing niobium can be performed to obtain deformed austenite prior to transformation. Accelerated cooling can be employed to refine the final microstructure and, consequently, to improve both strength and toughness. This general rule is fulfilled if the transformation occurs on a quite homogeneous austenite microstructure. Nevertheless, the presence of coarse austenite grains before transformation in different industrial processes is a usual source of concern, and regarding toughness, the coarsest high-angle boundary units would determine its final value. Sets of deformation dilatometry tests were carried out using three 0.06 pct Nb microalloyed steels to evaluate the effect of Mo alloying additions (0, 0.16, and 0.31 pct Mo) on final transformation from both recrystallized and unrecrystallized coarse-grained austenite. Continuous cooling transformation (CCT) diagrams were created, and detailed microstructural characterization was achieved through the use of optical microscopy (OM), field emission gun scanning electron microscopy (FEGSEM), and electron backscattered diffraction (EBSD). The resultant microstructures ranged from polygonal ferrite (PF) and pearlite (P) at slow cooling ranges to bainitic ferrite (BF) accompanied by martensite (M) for fast cooling rates. Plastic deformation of the parent austenite accelerated both ferrite and bainite transformation, moving the CCT curves to higher temperatures and shorter times. However, an increase in the final heterogeneity was observed when BF packets were formed, creating coarse high-angle grain boundary units.


Ferrite Austenite Bainite High Cool Rate Bainitic Ferrite 
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.



Financial support of this work by the Spanish Science and Innovation Department (MAT2009-09250 project) is gratefully acknowledged. One of the authors (NI) acknowledges a research grant from the University of Navarra. PU is grateful to NSF and TMS for the MS&T’10 Conference registration fee funding.


  1. 1.
    G.I. Garcia: Int. Conf. Microalloying ‘95, ISS, Warrendale, PA, 1995, pp. 365–75.Google Scholar
  2. 2.
    S.G. Jansto: New Developments on Metallurgy and Applications of High Strength Steels Conf., Buenos Aires, 2008, TMS, Warrendale, PA, pp. 1313–26.Google Scholar
  3. 3.
    N.A. McPherson: Ironmaking and Steelmaking, 2009, vol. 36, pp. 193–200.CrossRefGoogle Scholar
  4. 4.
    E.J. Czyryca, D.P. Kihl, and R. DeNale: AMPTIAC Q., 2003, vol. 7, pp. 63–70.Google Scholar
  5. 5.
    B. Dutta, E. Valdés, and C.M. Sellars: Acta Metall. Mater., 1992, vol. 40, pp. 652–62.Google Scholar
  6. 6.
    M.G. Akben, I. Weiss, and J.J. Jonas: Acta Metall., 1981, vol. 29, pp. 111–21.CrossRefGoogle Scholar
  7. 7.
    O. Kwon, and A.J. DeArdo: Acta Metall. Mater., 1991, vol. 39, pp. 529–38.CrossRefGoogle Scholar
  8. 8.
    D.N. Hanlon, J. Sietsma, and S. van der Zwaag: ISIJ Int., 2001, vol. 41, pp. 1028–36.CrossRefGoogle Scholar
  9. 9.
    Y. van Leeuwen and J. Sietsma: Mater. Sci. Forum, 2007, vols. 539–543, pp. 4572–77.CrossRefGoogle Scholar
  10. 10.
    S. Cai and J.D. Boyd: Mater. Sci. Forum, 2005, vols. 500–501, pp. 171–78.CrossRefGoogle Scholar
  11. 11.
    H. Asahi, A. Yagi, and M. Ueno: Metall. Mater. Trans. A, 1998, vol. 29A, pp. 1375–81.CrossRefGoogle Scholar
  12. 12.
    T. Tanaka: Int. Met. Rev., 1981, vol. 26, pp. 185–212.Google Scholar
  13. 13.
    H. Meuser, F. Grimpe, S. Meimeth, C.J. Heckmann, and C. Träger: Mater. Sci. Forum, 2005, vols. 500–501, pp. 565–72.CrossRefGoogle Scholar
  14. 14.
    D. Chakrabarti, M. Strangwood, and C. Davis: Metall. Mater. Trans. A, 2009, vol. 40A, pp. 780–95.CrossRefGoogle Scholar
  15. 15.
    P. Uranga, A.I. Fernández, B. López, and J.M. Rodriguez-Ibabe: 43rd Mechanical Working and Steel Processing Conf., ISS, Warrendale, PA, 2001, vol. 33, pp. 511–29.Google Scholar
  16. 16.
    B.L. Bramfitt and J.G. Speer: Metall. Trans. A, 1990, vol. 21A, pp. 817–29.Google Scholar
  17. 17.
    T. Araki, I. Kozasu, H. Tankechi, K. Shibata, M. Enomoto, and H. Tamehiro, eds., Atlas for Bainitic Microstructures, ISIJ, Tokyo, 1992, vol. 1.Google Scholar
  18. 18.
    H.I. Aaronson and H.A. Domian: Trans. AIME, 1966, vol. 236, pp. 781–96.Google Scholar
  19. 19.
    M. Hillert: in Solid-Solid Phase Transformations, H.I. Aaronson, D.E. Laughlin, R.F. Sekerka, and C.M. Wayman, eds., TMS, Warrendale, PA, 1982, pp. 789–806.Google Scholar
  20. 20.
    D.E. Coates: Metall. Trans., 1973, vol. 4, pp. 2313–25.CrossRefGoogle Scholar
  21. 21.
    T.B. Massalski: in Phase Transformations, ASM, Metals Park, OH, 1970, pp. 433–95.Google Scholar
  22. 22.
    M. Hillert: Metall. Trans. A, 1984, vol. 15A, pp. 411–19.Google Scholar
  23. 23.
    J. Cawley, C.F. Harris, and E.A. Wilson: New Aspects of Microstructures in Modern Low Carbon High Strength Steels Symp., ISIJ, Tokyo, 1994, pp. 11–14.Google Scholar
  24. 24.
    K. Shibata and K. Asakura: New Aspects of Microstructures in Modern Low Carbon High Strength Steels Symp., ISIJ, Tokyo, 1994, pp. 31–34.Google Scholar
  25. 25.
    G. Krauss and S.W. Thompson: ISIJ Int., 1995, vol. 35, pp. 937–45.CrossRefGoogle Scholar
  26. 26.
    H.K.D.H. Bhadeshia: Bainite in Steels, Transformations, Microstructure and Properties, 2nd ed., The Institute of Materials, London, 2001, pp. 277–79.Google Scholar
  27. 27.
    H.J. Lee, G. Spanos, G.J. Shiflet, and H.I. Aaronson: Acta Metall., 1988, vol. 36, pp. 1129–40.CrossRefGoogle Scholar
  28. 28.
    S. Zajac, V. Schwinn, and K.H. Tacke: Mater. Sci. Forum, 2005, vols. 500–501, pp. 387–94.CrossRefGoogle Scholar
  29. 29.
    R.F. Speyer: Thermal Analysis of Material, Marcel Dekker, Inc., New York, NY, 1994.Google Scholar
  30. 30.
    C. García de Andrés, F.B. Caballero, C. Capdevila, and H.K.D.H. Bhadeshia: Scripta Mater., 1998, vol. 39, pp. 791–96.CrossRefGoogle Scholar
  31. 31.
    ABAQUS Reference Manuals, Dassault Systèmes, Providence, RI, 2009.Google Scholar
  32. 32.
    R. Petrov, L. Kestens, and Y. Houbaert: Mater. Charact., 2004, vol. 53, pp. 51–61.CrossRefGoogle Scholar
  33. 33.
    P. Cizek, B.P. Wynne, C.H.J. Davies, B.C. Muddle, and P.D. Hodgson: Metall. Mater. Trans. A, 2002, vol. 33A, pp. 1331–49.CrossRefGoogle Scholar
  34. 34.
    P.A. Manohar, T. Chandra, and C.R. Killmore: ISIJ Int., 2006, vol. 36, pp. 1486–93.CrossRefGoogle Scholar
  35. 35.
    I. Tamura: Int. Conf. Thermec ‘88, ISIJ, Tokyo, 1988, pp. 1–10.Google Scholar
  36. 36.
    T. Tanaka: Int. Conf. Microalloying 95, M. Korchynsky, A.J. DeArdo, P. Repas, and G. Tither, eds., Pittsburgh, ISS, Warrendale, PA, 1995, pp. 165–81.Google Scholar
  37. 37.
    R. Bengochea, B. Lopez, and I. Gutierrez: Metall. Mater. Trans. A, 1998, vol. 29A, pp. 417–26.CrossRefGoogle Scholar
  38. 38.
    R. Bengochea, B. Lopez, and I. Gutierrez: in Microalloying in Steels (μ-as 98), J.M. Rodriguez-Ibabe, I. Gutierrez, and B. Lopez, eds., San Sebastian, Spain, 1998, pp. 201–08.Google Scholar
  39. 39.
    H.K.D.H. Bhadeshia: Bainite in Steels, Transformations, Microstructure and Properties, 2nd ed., The Institute of Materials, London, 2001, pp. 201–24.Google Scholar
  40. 40.
    A. Kazimierz and J. Lis: Mater. Sci. Forum, 2007, vol. 539–543, pp. 4620–25.Google Scholar
  41. 41.
    M. Umemoto, Z.H. Guo, and I. Tamura: Mater. Sci. Technol., 1987, vol. 3, pp. 249–55.Google Scholar
  42. 42.
    S. Zajac, T. Siwecki, B. Hutchinson, and M. Attlegard: Metall. Trans. A, 1991, vol. 22A, pp. 2681–94.Google Scholar
  43. 43.
    J.H. Beynon and C.M. Sellars: High Strength Low Alloy Steels Conf., Wollongong, 1984, TMS, Warrendale, PA, 1984, pp. 142–50.Google Scholar
  44. 44.
    A. From and R. Sandström: Mater. Charact., 1999, vol. 42, pp. 111–22.CrossRefGoogle Scholar
  45. 45.
    T. Hanamura, F. Yin, and K. Nagai: ISIJ Int., 2004, vol. 44, pp. 610–17.CrossRefGoogle Scholar
  46. 46.
    T. Furuhara, H. Kawata, S. Morito, and T. Maki: Mater. Sci. Eng. A, 2006, vol. A431, pp. 228–36.Google Scholar
  47. 47.
    T. Furuhara, N. Takayama, and G. Miyamoto: Mater. Sci. Forum, 2010, vols. 638–642, pp. 3044–49.CrossRefGoogle Scholar
  48. 48.
    A. Lambert-Perlade, A.F. Gourgues, and A. Pineau: Acta Mater., 2004, vol. 52, pp. 2337–48.CrossRefGoogle Scholar
  49. 49.
    K. Fujiwara, S. Okaguchi, and H. Ohtani: ISIJ Int., 1995, vol. 35, pp. 1006–12.CrossRefGoogle Scholar
  50. 50.
    K. Fujiwara and S. Okaguchi: Mater. Sci. Forum, 1998, vols. 284–286, pp. 271–78.CrossRefGoogle Scholar
  51. 51.
    R.Y. Zhang and J.D. Boyd: Metall. Mater. Trans. A, 2010, vol. 41A, pp. 1448–59.CrossRefGoogle Scholar

Copyright information

© The Minerals, Metals & Materials Society and ASM International 2011

Authors and Affiliations

  • N. Isasti
    • 1
  • D. Jorge-Badiola
    • 1
  • M. L. Taheri
    • 2
  • B. López
    • 1
  • P. Uranga
    • 1
  1. 1.CEIT and TECNUN (University of Navarra)Donostia-San SebastianBasque Country, Spain
  2. 2.Materials DepartmentDrexel UniversityPhiladelphiaUSA

Personalised recommendations