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Verhandlungen pp 621-628 | Cite as

Some special aspects of the bainitic structure

  • L. Habraken
Chapter

Abstract

Bainite is commonly thought of as a structure of carbides in ferrite and, in fact, is so defined. The carbides are of the M3C type. Some recent reviews of the bainitic transformation confirm this point of view (1). As reported some years ago in several publications (2,3, 4, 5, 6, 7, 8, 9), upper and lower bainite are differentiated in electron metallography by the orientation of the carbide particles with respect to the axis of the ferrite needle. In pure lower bainite, the carbides are parallel and lie at a constant angle with the direction of the bainitic needle (or lens). In pure upper bainite, a feather-like product, the carbides are parallel to the longest direction of the plates — one of the growth directions. These structures are exhibited in Fig. 1, a Cr-V steel, and in Fig. 2, an eutectoid carbon steel. Usually, these two structures appear in all steels containing 0.5% carbon and more, with and without other alloying elements. Here, the pearlitic transformation overlaps the upper portion of the bainitic range. The coexistence of these two structures is especially noticed in anisothermal transformation. In isothermal transformation, it is relatively easy to separate them.
Fig 187_1

Lower bainite in a Cr-V steel. Isothermal transformation 4 min 50 sec at 290°C. Formvar replica shadowed with chromium

Fig 187_2

Upper bainite in an eutectoid steel (0.9% C). Isothermal transformation 1 min at 525°C. Formvar replica shadowed with chromium

Fig 187_3

Granular structure in the upper region of the bainitic transformation in a Cr-Mo steel. (Light micrograph)

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References

  1. 1.
    Heieman, R. F., and A. R. Troiano: Metal Progr. 70, 97 (1956).Google Scholar
  2. 2.
    Coheur, P., et L. Habraken: Rev. nniv. Mines, 94, 107 (1951).Google Scholar
  3. 3.
    First Progress Report of Sub-Committee on Electron Microstructure of Steel, Proc. ASTM 50, 444 (1950).Google Scholar
  4. 4.
    Second Progr. Rep. by Sub-Ctee XI-Ctee E4, Proc. ASTM 52, 543 (1952).Google Scholar
  5. 5.
    Fourth Progr. Rep. by Sub-Ctee of Ctee E4. Proc. ASTM 54, 568–590 (1954).Google Scholar
  6. 6.
    G. Teague, D. M., and S. T. Ross: Proc. ASTM 55, 590 (1955).Google Scholar
  7. 7.
    Habraken, L.: Sur la métallographie électronique (Publ. Vaillant-Carmanne ) 1953, Liège, Belgium.Google Scholar
  8. 8.
    — Rev. de Métallurgie 53, 930 (1956).Google Scholar
  9. 10.
    — C. R. de recherches. IRSIA (Belgium), no 19 (1957).Google Scholar
  10. 10.
    Hultgren, A.: Trans. A.S.M. 39, 915, 1005 (1947); Jernkontorets Ann. 135, 403 (1951).Google Scholar
  11. 11.
    Sims, P.: Gases in metals — ASM publication.Google Scholar
  12. 12.
    Koch, W., A Krisch. A. Schrader: Arch. Eisenhüttenwesen 8, 445 (1957).Google Scholar
  13. 13.
    Friedel, J.: Les dislocations. Paris: Gauthier-Villars 1956.Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1960

Authors and Affiliations

  • L. Habraken
    • 1
  1. 1.National Center of Metallurgical ResearchLiègeBelgium

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