Abstract
A continuous-cooling-transformation (CCT) diagram was determined for a high-strength low-alloy plate steel containing (in weight percent) 0.06 C, 1.45 Mn, 1.25 Cu, 0.97 Ni, 0.72 Cr, and 0.42 Mo. Dilatometric measurements were supplemented by microhardness testing, light microscopy, and transmission electron microscopy. The CCT diagram showed significant suppression of polygonal ferrite formation and a prominent transformation region, normally attributed to bainite formation, at temperatures intermediate to those of polygonal ferrite and martensite formation. In the intermediate region, ferrite formation in groups of similarly oriented crystals about 1 μm in size and containing a high density of dislocations dominated the transformation of austenite during continuous cooling. The ferrite grains assumed two morphologies, elongated or acicular and equiaxed or granular, leading to the terms “acicular ferrite” and “granular ferrite,” respectively, to describe these structures. Austenite regions, some transformed to martensite, were enriched in carbon and retained at interfaces between ferrite grains. Coarse interfacial ledges and the nonacicular morphology of the granular ferrite grains provided evidence for a phase transformation mechanism involving reconstructive diffusion of substitutional atoms. At slow cooling rates, polygonal ferrite and Widmanstätten ferrite formed. These latter structures contained low dislocation densities and e-copper precipitates formed by an interphase transformation mechanism.
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T.W. Montemarano, B.P. Sack, J.P. Gudas, M.G. Vassilaros, and H.H. Vanderveldt:J. Ship Production, 1986, vol. 2, pp. 145–62.
J.C. West:J. Ship Production, 1987, vol. 3, pp. 111–18.
R.J. Jesseman and G.J. Murphy:J. Heat Treat., 1984, vol. 3, pp. 228–36.
G.E. Hicho, C.H. Brady, L.C. Smith, and R.J. Fields:J. Heat Treat., 1987, vol. 5, pp. 7–19.
G.R. Speich and T.M. Scoonover: inProcessing, Microstructure and Properties of HSLA Steels, A.J. De Ardo, ed., TMS, Warrendale, PA, 1988, pp. 263–86.
M.T. Miglin, J.P. Hirth, A.R. Rosenfield, and W.A.T. Clark:Metall. Trans. A, 1986, vol. 17A, pp. 791–98.
A.D. Wilson, E.G. Hamburg, D.J. Colvin, S.W. Thompson, and G. Krauss:Microalloyed HSLA Steels, ASM INTERNATIONAL, Metals Park, OH, 1988, pp. 259–75.
C.S. Smith and E.W. Palmer:Trans. AIME, 1933, vol. 105, pp. 133–68.
E. Hornbogen:Trans. ASM, 1964, vol. 57, pp. 120–32.
R.A. DePaul and A.L. Kitchin:Metall. Trans., 1970, vol. 1, pp. 389–93.
First Progress Report of Subcommittee XI, ASTM Committee E-4:Proc. ASTM, 1950, vol. 50, pp. 444–92.
Second Progress Report of Subcommittee XI, ASTM Committee E-4:Proc. ASTM, 1952, vol. 52, pp. 543–96.
R.F. Hehemann:Metals Handbook, 8th ed., ASM, Metals Park, OH, 1972, vol. 8, pp. 194–96.
H.I. Aaronson:The Mechanism of Phase Transformations in Crystalline Solids, Monograph and Report Series No. 33, The Institute of Metals, London, 1969, pp. 270–81.
R.F. Hehemann, K.R. Kinsman, and H.I. Aaronson:Metall. Trans., 1972, vol. 3, pp. 1077–94.
H.I. Aaronson and H.J. Lee:Scripta Metall., 1987, vol. 21, pp. 1011–16.
J.W. Christian and D.V. Edmonds: inPhase Transformations in Ferrous Alloys, A.R. Marder and J.I. Goldstein, eds., TMS-AIME, Warrendale, PA, 1984, pp. 293–325.
G.B. Olson, H.K.D.H. Bhadeshia, and M. Cohen:Acta Metall., 1989, vol. 37, pp. 381–90.
S.W. Thompson, D.J. Colvin, and G. Krauss:Scripta Metall, 1988, vol. 22, pp. 1069–74.
B.L. Bramfitt and J.G. Speer:Metall. Trans. A, 1990, vol. 21A, pp. 817–29.
L.J. Habraken and M. Economopoulos:Transformation and Hardenability in Steels, Climax Molybdenum Company, Ann Arbor, MI, 1967, pp. 69–108.
Y.E. Smith, A.P. Coldren, and R.L. Cryderman:Toward Improved Ductility and Toughness, Climax Molybdenum Company, Ann Arbor, MI, 1971, pp. 119–42.
V. Biss and R.L. Cryderman:Metall. Trans., 1971, vol. 2, pp. 2267–76.
M.E. Bush and P.M. Kelly:Acta Metall., 1971, vol. 19, pp. 1363–71.
Z. Bojarski and T. Bold:Acta Metall., 1974, vol. 22, pp. 1223–34.
A. Brownrigg:Met. Sci., 1975, vol. 9, pp. 313–18.
E.C. Hamre and A.M. Gilroy-Scott:Proc. Microalloying '75, Union Carbide Corporation, New York, NY, 1977, pp. 375–81.
N.A. McPherson and T.N. Baker:Met. Sci., 1976, vol. 10, pp. 140–47.
P.L. Mangonon:Metall. Trans. A, 1976, vol. 7A, pp. 1389–1400.
H. Fang, Y. Zheng, and B. Bai: inHSLA Steels: Metallurgy and Applications, J.M. Gray, T. Ko, S. Zhang, B. Wu, and X. Xie, eds., ASM INTERNATIONAL, Metals Park, OH, 1986, pp. 359–67.
T. Araki, K. Shibata, and M. Enomoto:ICOMAT '89, in press.
1990 Annual Book of ASTM Standards, ASTM Designation A710, ASTM, Philadelphia, PA, 1990, vol. 01.04, pp. 500–02.
D.J. Colvin: M.S. Thesis, Colorado School of Mines, Golden, CO, 1988.
K.W. Andrews:J. Iron Steel Inst., 1965, vol. 203, pp. 721–27.
W. Steven and A.G. Haynes:J. Iron Steel Inst., 1956, vol. 183, pp. 349–59.
C.F. ZurLippe and J.D. Grozier: inAtlas of Isothermal Transformation and Cooling Transformation Diagrams, ASM, Metals Park, OH, 1977, pp. 416–17.
G. Krauss: inHardenability Concepts with Applications to Steel, D.V. Doane and J.S. Kirkaldy, eds., TMS-AIME, Warrendale, PA, 1978, pp. 229–48.
R. Blondeau, Ph. Maynier, J. Dollet, and B. Vieillard-Baron:Heat Treatment '76, The Metals Society, London, 1976, pp. 189–200.
H.K.D.H. Bhadeshia and J.W. Christian:Metall. Trans. A, 1990, vol. 21A, pp. 767–97.
A.R. Marder and G. Krauss:Trans. ASM, 1967, vol. 60, pp. 651–60.
H.I. Aaronson and W.T. Reynolds, Jr.:Scripta Metall., 1988, vol. 22, pp. 567–72.
R.N. Caron and G. Krauss:Metall. Trans., 1972, vol. 3, pp. 2381–89.
H.I. Aaronson and C. Wells:Trans. AIME, 1956, vol. 206, pp. 1216–23.
J.M. Oblak and R.F. Hehemann:Transformation and Hardenability in Steels, Climax Molybdenum Company, Ann Arbor, MI, 1967, pp. 15–38.
E.S.K. Menon and H.I. Aaronson:Acta Metall., 1987, vol. 35, pp. 549–63.
V. Raghavan and A.R. Entwisle:Physical Properties of Martensite and Bainite, ISI Special Report No. 93, 1965, pp. 30–37.
G. Kurdjumov and G. Sachs:Z.Phys., 1930, vol. 64, pp. 325–43.
Z. Nishiyama:Sci. Rep. Tohoku Univ., 1934, vol. 23, pp. 637–64.
G. Wassermann:Arch. Eisenhüttenwes., 1933, vol. 16, pp. 647–54.
P.G. Boswell, K.R. Kinsman, G.J. Shiflet, and H.I. Aaronson: inMechanical Properties and Phase Transformations in Engineering Materials, S.D. Antolovich, R.O. Ritchie, and W.W. Gerberich, eds., TMS-AIME, Wanendale, PA, 1986, pp. 445–66.
H. Tsubakino and H.I. Aaronson:Metall. Trans. A, 1987, vol. 18A, pp. 2047–60.
H.I. Aaronson: inDecomposition of Austenite by Diffusional Processes, V.F. Zackay and H.I. Aaronson, eds., Interscience, New York, NY, 1962, pp. 387–548.
R.W.K. Honeycombe:Metall. Trans. A, 1976, vol. 7A, pp. 915–36.
R.A. Ricks, P.R. Howell, and R.W.K. Honeycombe:Met. Sci., 1980, vol. 14, pp. 562–68.
M. Cohen, G.B. Olson, and P.C. Clapp:ICOMAT '79, MIT, Cambridge, MA, 1979, pp. 1–11.
H.K.D.H. Bhadeshia:Scripta Metall., 1987, vol. 21, pp. 1017–22.
J.W. Christian:Acta Metall., 1958, vol. 6, pp. 377–79.
H.K.D.H. Bhadeshia:Worked Examples in the Geometry of Crystals, Institute of Metals, Brookfield, VT, 1987, p. 57.
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Formerly Graduate Student, Department of Metallurgical and Materials Engineering, Colorado School of Mines.
This paper is based on a presentation made in the symposium “International Conference on Bainite” presented at the 1988 World Materials Congress in Chicago, IL, on September 26 and 27, 1988, under the auspices of the ASM INTERNATIONAL Phase Transformations Committee and the TMS Ferrous Metallurgy Committee.
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Thompson, S.W., Vin Col, D.J. & Krauss, G. Continuous cooling transformations and microstructures in a low-carbon, high-strength low-alloy plate steel. Metall Trans A 21, 1493–1507 (1990). https://doi.org/10.1007/BF02672564
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DOI: https://doi.org/10.1007/BF02672564