Thermal dependence of austempering transformation kinetics of compacted graphite cast iron
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Abstract
The evolution of the relative fraction of high-carbon austenite with austempering time and temperature was analyzed in a compacted graphite (CG) cast iron (average composition, in wt pct: 3.40C, 2.8Si, 0.8Mn, 0.04Cu, 0.01P, and 0.02S) at five different austempering temperatures between 573 and 673 K. Samples were characterized by Mössbauer spectroscopy, hardness measurements, and optical microscopy. During the first stage of transformation, the kinetics parameters were determined using the Johnson-Mehl’s equation, and their dependence with temperature in the range from 573 to 673 K indicates that the transformation is governed by nucleation and growth processes. The balance between growth-rate kinetics and nucleation kinetics causes the kinetics parameter (k) to have a maximum at ≈623 K of 3.9×10−3(s−1). The evolution of the C content in the high-carbon austenite was found to be controlled by the volume diffusion of carbon atoms from the ferrite/austenite interface into austenite, with a dependence of t 0.40±0.05 on the austempering time (t).
Keywords
Ferrite Austenite Martensite Material Transaction Cast IronPreview
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References
- 1.N. Darwish and R. Elliott: Mater. Sci. Technol., 1993, vol. 9 (7), pp. 572–85.Google Scholar
- 2.N. Darwish and R. Elliott: Mater. Sci. Technol., 1993, vol. 9 (7), pp. 586–602.Google Scholar
- 3.B.T. Sim and R. Elliott: Mater. Sci. Technol., 1998, vol. 14 (2), pp. 89–96.Google Scholar
- 4.H. Bayati, A.L. Rimmer, and R. Elliott: Cast Met., 1994, vol. 7 (1), pp. 11–24.Google Scholar
- 5.C.N.R. Rao and K.J. Rao: Phase Transitions in Solids, McGraw-Hill, New York, NY, 1978, pp. 81–95.Google Scholar
- 6.J.W. Christian: The Theory of Transformation in Metals and Alloys, Pergamon Press, Oxford, United Kingdom, 1965, pp. 525–48.Google Scholar
- 7.H.I. Aaronson and J.K. Lee: in Lectures on the Theory of Phase Transformation, H.I. Aaronson ed., AIME, New York, NY, 1975, pp. 83–115.Google Scholar
- 8.R.D. Doherty: in Physical Metallurgy, R.W. Cahn and P. Haansen, eds., North-Holland, Amsterdam, 1996, pp. 1363–1505.Google Scholar
- 9.C. Zener: J. App. Phys., 1949, vol. 20, pp. 950–53.CrossRefGoogle Scholar
- 10.H.B. Aaron, D. Fainstein, and G.R. Kotler: J. Appl. Phys., 1970, vol. 41, pp. 4404–10.CrossRefGoogle Scholar
- 11.J. Desimoni, R. Gregorutti, K. Laneri, J.L. Sarutti, and R.C. Mercader: Metall. Mater. Trans. A, 1999, vol. 30A, pp. 2745–53.CrossRefGoogle Scholar
- 12.S.F. Hubert: J. Br. Ceram. Soc., 1969, p. 11; as quoted by Ref. 14.Google Scholar
- 13.J. Philibert: Atoms Movements, Diffusion and Mass Transport in Solids, Les éditions de Physique, Les Ulis, France, 1991, p. 7.Google Scholar
- 14.Y.C. Liu, J.M. Schissler, and A. Munteanu: La Rev. Mét., 1994, vol. 91 (5), pp. 815–26.Google Scholar
- 15.D.G. Rancourt, A.M. McDonald, A.E. Lalonde, and J.Y. Ping: Am. Mineralogist, 1993, vol. 78, pp. 1–7.Google Scholar
- 16.M. Ron: in Applications of Mässbauer Spectroscopy, R.L. Cohen, ed., Academic Press, New York, NY, 1976, vol. II, pp. 329–88.Google Scholar
- 17.O.N.C. Uwakweh, J.P. Bauer, and J.M. Génin: Metall. Trans. A, 1990, vol. 21A, pp. 589–602.Google Scholar
- 18.L. Kaufman and S.V. Radcliffe: in Decomposition of Austenite by Diffusional Processes, V.F. Zackay and H.I. Aaronson, eds., Interscience, New York, NY, 1962, pp. 313–51.Google Scholar
- 19.J.W. Christian: in Physical Metallurgy, R.W. Cahn, ed., North-Holland Publishimg Company, Amsterdam, 1970, pp. 516–27.Google Scholar