Metals and Materials

, 4:125 | Cite as

Morphology and growth process of bainitic ferrite in steels

  • Yun-Chul Jung
  • Sung-Joon Kim
  • Yasuya Ohmori
Article
  • 263 Downloads

Abstract

The morphologies and the formation mechanisms of isothermally transformed Widmanstatten ferrite and bainite in various steels were investigated. Widmanstatten ferrite often grew from the grain boundary ferrite allotriomorph formed by a diffusional mechanism in the temperature range of the upper C-curve, whereas, bainite grew directly from an austenite grain boundary showing its own C-curve in a TIT diagram at temperatures between Bs (bainite starting temperature) and Ms (martensite starting temperature). Both structures accompanied well-defined surface reliefs of the invariant plane strain-type, and were in the shape of a lath or a plate consisting of several parallel needle-like ferrite subunits with parallelogram cross sc:ctions. The crystallographic properties of Widmanstatten ferrite and upper bainite were similar to those of lath martensite. Therefore, it was concluded that the difference between bainitic ferrite and Widmanstatten ferrite existed only in the nucleation events, where both structures grew by the same mechanism.

Key words

morphology Widmanstätten ferrite bainitic ferrite upper bainite lower bainite surface relief martensite crystallography mechanism 

References

  1. 1.
    T. Araki, K. Shibata and M. Enotnoto,Mater. Sci. Forum 56, 275 (1990).CrossRefGoogle Scholar
  2. 2.
    G. R. Purdy and M. Hillert,Acta metall. 32, 823 (1984).CrossRefGoogle Scholar
  3. 3.
    J. D. Watson and P. G. McDougall,Acta metall. 21, 961 (1973).CrossRefGoogle Scholar
  4. 4.
    T. Ko and S. A. Cottrell,JISI 172, 307 (1952).Google Scholar
  5. 5.
    K. R. Kinsman, E. Eichen and H. I. Aaronson,Metall. Trans. 6A, 303 (1975).Google Scholar
  6. 6.
    M. Takahashi and H. K. D. H. Bhadeshia,Mater. Sci. and Tech. 6, 592 (1990).Google Scholar
  7. 7.
    Y. Ohmori, H. Ohtsubo, Y. C. Jung, S. Okaguchi and H. Ohtani,Metall. Trans. 25A, 1981 (1994).Google Scholar
  8. 8.
    Y. Ohmori, H. Ohtani and T. Kunitake,Trans. ISIJ 11, 250 (1971).Google Scholar
  9. 9.
    H. Ohtani, S. Okaguchi, Y. Fujishiro and Y. Ohmori,Metall. Trans. 21A, 877 (1990).Google Scholar
  10. 10.
    M. Oka, H. Okamoto and K. Ishida,Metall. Trans. 21A, 845 (1990).Google Scholar
  11. 11.
    Y. Ohmori,Mater. Trans. JIM 30, 487 (1989).Google Scholar
  12. 12.
    J. W. Christian,Metall. Trans. 21A, 799 (1990).Google Scholar
  13. 13.
    R. F. Hehemann, K. R. Kinsman and H. I. Aaronson,Metall. Trans. 2, 1077 (1972).CrossRefGoogle Scholar
  14. 14.
    H. Goldstein and H. I. Aaronson.Metall. Trans. 21A, 1465 (1990).Google Scholar
  15. 15.
    J. R. Bradley and H. I. Aaronson,Metall. Trans. 12A, 1729 (1981).Google Scholar
  16. 16.
    Y. C. Jung, K. Nakai, H. Ohtsubo and Y. Ohmori,ISIJ Int. 34, 43 (1994).CrossRefMATHGoogle Scholar
  17. 17.
    Y. Ohmori,ISIJ Int. 35, 962 (1995).CrossRefGoogle Scholar
  18. 18.
    H. K. D. H. Bhadeshia and D. V. Edmonds,Acta metall. 28, 1265 (1980).CrossRefGoogle Scholar
  19. 19.
    H. K. D. H. Bhadeshia and J. W. Christian,Metall. Trans. 21A, 767 (1990).Google Scholar
  20. 20.
    J. M. Rigsbee and H. I. Aaronson,Acta metall. 27, 351 (1979).CrossRefGoogle Scholar
  21. 21.
    G. J. Shiflet and H. I. Aaronson,Acta metall. 27, 377 (1979).CrossRefGoogle Scholar
  22. 22.
    G. B. Olson, H. K. D. H. Bhadeshia and M. Cohen,Acta metall. 37, 381 (1989).CrossRefGoogle Scholar
  23. 23.
    H. K. D. H. Bhadeshia,Acta metall 29, 1117 (1981).CrossRefGoogle Scholar
  24. 24.
    H. K. D. H. Bhadeshia,Met. Sci. 16, 159 (1982).Google Scholar
  25. 25.
    K. Tsuzaki, A. Kodai and T. Maki,Mater. Trans. JIM 32, 667 (1991).Google Scholar
  26. 26.
    M. Enomoto and H. Tsubakino,Bulletin Japan Inst. Metals. 28, 732 (1989).Google Scholar
  27. 27.
    H. I. Aaronson,Decomposition of Austenite by Diffusional Processes (eds., V. F. Zackay and H. I. Aaronson), p. 387, Interscience, New York, NY (1962).Google Scholar
  28. 28.
    S. A. Mujahid and H. K. D. H. Bhadeshia,Acta metall. 41, 967 (1993).CrossRefGoogle Scholar
  29. 29.
    Y. Ohmori, K. Nakai, H. Ohtsubo and Y. Isshiki,ISIJ Intl. 35, 969 (1995).CrossRefGoogle Scholar
  30. 30.
    P. L. Ryder and W. Pitsch,Acta metall. 14, 1437 (1966).CrossRefGoogle Scholar
  31. 31.
    G. Kurdjumov and G. Sachs,Z. Physik. 64, 325 (1930).CrossRefADSGoogle Scholar

Copyright information

© Springer 1998

Authors and Affiliations

  • Yun-Chul Jung
    • 1
  • Sung-Joon Kim
    • 1
  • Yasuya Ohmori
    • 2
    • 1
  1. 1.Materials Engineering DepartmentKorea Institute of Machinery & MaterialsKyungnamKorea
  2. 2.Department of Materials Science & EngineeringFaculty of Engineering, Ehime UniversityMatsuyama 790Japan

Personalised recommendations