Abstract
Information on the diffusional transformation products of austenite in high-carbon steels is reviewed and supplemented with new microscopic studies. A comparison with transformation products in low-carbon steels indicates that there is a symmetry with pearlite in the middle, where ferrite and cementite are equal partners, and with acicular ferrite or cementite on each side. They both form with a surface relief, and at lower temperatures, each one is the leading phase in a eutectoid microstructure, bainite and inverse bainite, respectively. However, there is an asymmetry because at low temperatures bainite appears in high-carbon steels but inverse bainite never appears in low-carbon steels. At a constant high carbon content, there is another kind of symmetry, which is related to temperature. At intermediate temperatures the eutectoid reaction results in spherical nodules in which the cementite constituent originates from Widmanstätten plates. It turns spiky at both higher and lower temperatures with the leading phase in the spikes being cementite at higher temperatures and ferrite at lower temperatures. In the first kind of symmetry, there is an abrupt change among the three reaction products; in the second kind of symmetry, there is a gradual change. Accepting that all the eutectoid microstructures form by diffusion of carbon, one may explain the existence of both symmetries by the variation of the ratio of the supersaturations of ferrite and cementite with carbon content and with temperature.
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References
M. Hillert: Jernkont. Ann., 1957, vol. 141, pp. 757-89.
C. Zener: Trans. AIME, 1946, vol. 167, pp. 550-83.
K.R. Kinsman and H.I. Aaronson: Metall. Trans., 1970, vol. 1, pp. 1485-88.
H.J. Lee, G. Spanos, G.J. Shiflet, and H.I. Aaronson: Acta Metall., 1988, vol. 36, pp. 1129-40.
G. Spanos, H.S. Fang, D.S. Sarma, and H.I. Aaronson: Metall. Trans. A, 1990, vol. 21A pp. 1391-1411.
T. Ko and S.A. Cottrell: J. Iron Steel Inst., 1951, vol. 172, pp. 307-13.
K. Tsuya: J. Mech. Lab. Jpn., 1956, vol. 2, pp. 20-27.
J.M. Oblak and R.F. Hehemann: Transformation and Hardenability in Steels, Climax Molybdenum Co., Ann Arbor, MI, 1967, pp. 15-38.
A. Borgenstam, M. Hillert, and J. Ågren: Acta Mater., 2009, vol. 57, pp. 3242-52.
A. Borgenstam, M. Hillert, and J. Ågren: Scripta Mater., 2010, vol. 62, pp. 75-77.
J.O. Anderson, T. Helander, L. Höglund, P.F. Shi, and B. Sundman, CALPHAD, 2002, vol. 26, pp. 273-312.
T. Ko: J. Iron Steel Inst., 1953, vol. 175, pp. 16-18.
G.R. Speich: Unpublished work, reproduced by H. Warlimont in a report from the Edgar C. Bain Laboratory for Fundamental Research, U.S. Steel Corporation, Monroeville, PA, 1961.
J.-Y. Yan and W.-Z. Zhang: Unpublished report, Tsinghua University, Beijing, China, 2009.
H. Modin and S. Modin: Jernkont. Ann., 1955, vol. 139, pp. 481-515.
S. Modin: Jernkont. Ann., 1958, vol. 142, pp. 37-80.
H. Modin and S. Modin: Microstructures in Three Isothermally Transformed Carbon Steels with High-carbon Contents, Meritförlaget, Stockholm, Sweden, 2000.
A.B. Greninger and A.R. Troiano: Trans. AIME, 1940, vol. 140, pp. 307-31.
A. Hultgren: Jernkont. Ann., in Swedish, 1951, vol. 135, p. 403, Kungl. Vetensk. Akad. Handl., in English, 1953, Stockholm, Sweden, vol. 4 (3).
T.G. Nilan: Trans. AIME, 1967, vol. 239, pp. 898-909.
J.R. Vilella: Trans. AIME, 1940, vol. 140, pp. 332-34.
H. Modin and S. Modin: Metallurgical Microscopy, Butterworths, London, UK, 1973, p. 376.
H. Warlimont: The Iron and Steel Institute, Special Report 93, London, UK, 1965, pp.149–51.
H. Okamoto and M. Oka: Metall. Trans. A, 1986, vol. 17A, pp. 1113-20.
M. Hillert: Decomposition of Austenite by Diffusional Processes, Eds. V.F. Zackay and H.I. Aaronson, Wiley, New York, NY, 1962, pp. 197-247.
M. Oka, H. Okamoto, and K. Ishida: Metall. Trans. A, 1990, vol. 21A, pp. 845-51.
E.R. Kuteliya: Fiz. Metal. Metalloved., 1969, vol. 28, pp. 853-57.
H. Okamoto and M. Oka: Metall. Trans. A, 1985, vol. 16A, pp. 2257-62.
H.K.D.H. Bhadeshia: Bainite in Steels, 2nd ed., University Press, Cambridge, MA, 2001.
M. Hillert: “The Growth of Ferrite, Bainite and Martensite,” Report, Swedish Inst. Metal Res. Stockholm 1960, reprinted in Thermodynamics and Phase Transformations, The selected works of Mats Hillert, J. Ågren, Y. Bréchet, C. Hutchinson, J. Philibert, and G. Purdy, eds., EDP Sciences, Les Ulis Cedex A, France, 2006, pp. 113–58.
M. Hillert, L. Höglund, and J. Ågren: Metall. Mater. Trans. A, 2004, vol. 35A, pp. 3693-3700.
M. De Graef, M.V. Kral, and M. Hillert: JOM, 2006, pp. 25–28.
Acknowledgments
This work was inspired by the metallographic atlas produced by Helfrid and Sten Modin. The authors are grateful for the permission to reproduce their micrographs for the current work. It was performed within the VINN Excellence Center Hero-m, financed by VINNOVA, the Swedish Governmental Agency for Innovation Systems, Swedish industry, and KTH (Royal Institute of Technology).
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Manuscript submitted January 25, 2010.
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Borgenstam, A., Hedström, P., Hillert, M. et al. On the Symmetry Among the Diffusional Transformation Products of Austenite. Metall Mater Trans A 42, 1558–1574 (2011). https://doi.org/10.1007/s11661-010-0539-1
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DOI: https://doi.org/10.1007/s11661-010-0539-1