Metallurgical and Materials Transactions A

, Volume 32, Issue 6, pp 1507–1517

Nucleation sites for ultrafine ferrite produced by deformation of austenite during single-pass strip rolling

  • P. J. Hurley
  • B. C. Muddle
  • P. D. Hodgson
Article

Abstract

An austenitic Ni-30 wt pct Fe alloy, with a stacking-fault energy and deformation characteristics similar to those of austenitic low-carbon steel at elevated temperatures, has been used to examine the defect substructure within austenite deformed by single-pass strip rolling and to identify those features most likely to provide sites for intragranular nucleation of ultrafine ferrite in steels. Samples of this alloy and a 0.095 wt pct C-1.58Mn-0.22Si-0.27Mo steel have been hot rolled and cooled under similar conditions, and the resulting microstructures were compared using transmission electron microscopy (TEM), electron diffraction, and X-ray diffraction. Following a single rolling pass of ∼40 pct reduction of a 2mm strip at 800 °C, three microstructural zones were identified throughout its thickness. The surface zone (of 0.1 to 0.4 mm in depth) within the steel comprised a uniform microstructure of ultrafine ferrite, while the equivalent zone of a Ni-30Fe alloy contained a network of dislocation cells, with an average diameter of 0.5 to 1.0 µm. The scale and distribution and, thus, nucleation density of the ferrite grains formed in the steel were consistent with the formation of individual ferrite nuclei on cell boundaries within the austenite. In the transition zone, 0.3 to 0.5 mm below the surface of the steel strip, discrete polygonal ferrite grains were observed to form in parallel, and closely spaced “rafts” traversing individual grains of austenite. Based on observations of the equivalent zone of the rolled Ni-30Fe alloy, the ferrite distribution could be correlated with planar defects in the form of intragranular microshear bands formed within the deformed austenite during rolling. Within the central zone of the steel strip, a bainitic microstructure, typical of that observed after conventional hot rolling of this steel, was observed following air cooling. In this region of the rolled Ni-30Fe alloy, a network of microbands was observed, typical of material deformed under plane-strain conditions.

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References

  1. 1.
    R. Priestner and E. de los Rios: Met. Technol., 1980, pp. 309–16.Google Scholar
  2. 2.
    P.D. Hodgson, M.R. Hickson, and R.K. Gibbs: Mater. Sci. Forum, 1998, vols. 284–286, pp. 63–73.Google Scholar
  3. 3.
    X.J. Zhang, P.D. Hodgson, and P.F. Thomson: J. Mater. Processing Technol., 1996, vol. 60, pp. 615–620.CrossRefGoogle Scholar
  4. 4.
    P.J. Hurley and P.D. Hodgson: Mater. Sci. Eng. A, 2001, vol. 302, issue 2, pp. 206–14.CrossRefGoogle Scholar
  5. 5.
    P.J. Hurley, B.C. Muddle, P.D. Hodgson, C.H.J. Davies, B.P. Wynne, P. Cizek, and M.R. Hickson: Mater. Sci. Forum, 1998, vols. 284–286, pp. 159–66.CrossRefGoogle Scholar
  6. 6.
    P. Cizek, D.G. McCulloch, and B.A. Parker: Proc. 13th Biennial Conf. of the Australian Society of Electron Microscopy—ACEM-13, Gold Coast, Australia, D. Allen, J. Barry, T. Bostrom, L.M. Hogan, and M.S. Pennisi, eds., The Australian Society of Electron Microscopy, Sydney, Australia, 7–11 February, 1994, p. 110.Google Scholar
  7. 7.
    B.D. Cullity, Elements of X-ray Diffraction, 2nd ed., Addison-Wesley Publishing Company, Reading, MA, 1978, p. 308.Google Scholar
  8. 8.
    H. Bunge: Texture Analysis in Materials Science: Mathematical Methods, 1st ed. Butterworth and Co., Berlin, 1982, pp. 1–41.Google Scholar
  9. 9.
    J.S. Kallend, U.F. Kocks, A.D. Rollett, and H.-R. Wenk: Mater. Sci. Eng. A, 1991, vol. A132, pp. 1–11.Google Scholar
  10. 10.
    M. Holscher, D. Raabe, and K. Lucke: Acta Metall. Mater., 1994, vol. 42 (3), pp. 879–86.CrossRefGoogle Scholar
  11. 11.
    D. Raabe: J. Mater. Sci., 1995, vol. 30, pp. 47–52.CrossRefGoogle Scholar
  12. 12.
    A. Korbel, J.D. Embury, M. Hatherly, P.L. Martin, and H.W. Erbsloh: Acta Metall. Mater., 1986, vol. 34 (10), pp. 1999–2009.CrossRefGoogle Scholar
  13. 13.
    C. Donadille, R. Valle, P. Dervin, and R. Penelle: Acta Metall. Mater., 1989, vol. 37 (6), pp. 1547–71.CrossRefGoogle Scholar
  14. 14.
    B. Bay, N. Hansen, D.A. Hughes, and D. Kuhlmann-Wilsdorf: Acta Metall. Mater., 1992, vol. 40 (2), pp. 205–19.CrossRefGoogle Scholar
  15. 15.
    P. Cizek: Monash University, Melbourne, unpublished research, 1998.Google Scholar
  16. 16.
    R. Kaspar, J.S. Disti, and O. Pawelski: Steel Res., 1988, vol. 59 (9), pp. 421–25.Google Scholar
  17. 17.
    F.H. Samuel, S. Yue, J.J. Jonas, and K.R. Barnes: Iron Steel Inst. Jpn. Int., 1990, vol. 30 (3), pp. 216–25.Google Scholar
  18. 18.
    P.J. Hurley, P.D. Hodgson, and B.C. Muddle: Scripta Mater., 1999, vol. 40 (4), pp. 433–38.CrossRefGoogle Scholar
  19. 19.
    P.J. Hurley: Ph.D. Thesis, Monash University, Melbourne, 1999.Google Scholar

Copyright information

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

Authors and Affiliations

  • P. J. Hurley
    • 1
  • B. C. Muddle
    • 2
  • P. D. Hodgson
    • 3
  1. 1.Manchester Materials Science CentreUMIST, and the University of ManchesterManchesterUnited Kingdom
  2. 2.the Department of Materials EngineeringMonash UniversityMelbourneAustralia
  3. 3.the School of Engineering and TechnologyDeakin UniversityGeelongAustralia

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