Abstract
The microstructural characteristics of melt-spun and heat-treated austenitic Fe−28Mn−8.6Al−0.5Mo−0.7W−0.5Nb−1.1C (in wt. %) alloys have been investigated by means of transmission electron microscopy. The melt-spun alloy contained fine austenitic cells and some intercelluar Nb(C, N) precipitates. Detailed observations revealed fine {100} modulations in the matrix of the cells, as well as a concomitant L′I2 atomic ordering arising from it. These observations indicate that the onset of decomposition of the initial austenite phase occurred during the rapid solidification process. Aging of the melt-spun alloy at 823–1173 K produced various microstructures, including a general precipitation of Nb(C, N) in the matrix. On isochronal annealing for 1 h, this matrix Nb(C, N) precipitation commenced at 1073 K with the formation of metastable coherent K-carbide (K′) near cell boundaries. On annealing at temperatures above 1123 K, only the Nb(C, N) precipitates were formed, on a fine scale, being accompanied by the formation of precipitate-free regions in the vicinity of cell and grain boundaries. Both intercellular and matrix Nb(C, N) precipitates obeyed a cube-to-cube orientation relationship with austenite. The general matrix precipitation of Nb(C, N) and formation of precipitate-free regions are discussed in terms of a vacancy (defect)-depletion effect. Finally, it was demonstrated that, by employing a double heat-treatment schedule of annealing at 1173 K followed by aging at 823 K, a novel microstructure consisting of fine dispersoids of Nb(C, N) carbo-nitride, distributed over the matrix of {100} modulated structure, could be produced.
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References
P.J. James, J. Iron Steel Inst. 207, 54 (1969).
G.L. Kayak, Met. Sci. Heat Treat. 11, 95 (1969).
G. S. Krivonogov, M. F. Alekseyenko, and G.G. Solov’yeva, Phys. Met. Metall. 39, 86 (1975).
K. H. Han, W. K. Choo, D. Y. Choi, and S. P. Hong, Alternate Alloying for Environmental Resistance, edited by S. K. Banerji and G.R. Smolik (TMS-AIME, Warrendale, PA, 1987), p. 91.
N. A. Storchak and A. G. Drachinskaya, Phys. Met. Metall. 44, 123 (1977).
K. H. Han, J. C. Yoon, and W. K. Choo, Scripta Metall. 20, 33 (1986).
K.H. Han and W. K. Choo, Metall. Trans. 20A, 205 (1989).
K. H. Han, W. K. Choo, and D. E. Laughlin, Scripta Metall. 22, 1873 (1988).
M.F. Alekseenko, G. S. Krivonogov, L. G. Kozyreva, I. M. Kachanova, and L. V. Arapova, Met. Sci. Heat Treat. 14, 187 (1972).
I.S. Kalashinikov, V.S. Litvinov, M.S. Khadyyev, and L.D. Chumakova, Phys. Met. Metall. 57, 160 (1984).
S. D. Karakishev, L. D. Chumakova, I. S. Kalashinikov, and A. A. Senchenko, Met. Sci. Heat Treat. 28 (7–8), 609 (1987).
J.V. Wood and R.W.K. Honeycombe, Mater. Sci. Eng. 23, 107 (1976).
J.V. Wood and R.W.K. Honeycombe, Philos. Mag. A37, 501 (1978).
K. H. Han and H. E. Lee, Scripta Metall. et Mater. 30, 441 (1994).
J.V. Wood and R.W.K. Honeycombe, J. Mater. Sci. 9, 1183 (1974).
J.W. Cahn, Acta Metall. 10, 179 (1962).
V. Daniel and H. Lipson, Proc. R. Soc. London A181, 368 (1943).
K.H. Han and W.K. Choo, Metall. Trans. 14A, 973 (1983).
S.D. Karakishev and I.S. Kalashinikov, Phys. Met. Metall. 62, 187 (1986).
J.M. Silcock, J. Iron Steel Inst. 201, 125 (1963).
M. A. P. Dewey, G. Sumner, and I. S. Brammer, J. Iron Steel Inst. 203, 938 (1965).
A.T. Davenport, L.C. Brossard, and R.E. Miner, J. Met. 27, 21 (1975).
A. G. Kachaturyan, Theory of Structural Transformations in Solids (John Wiley & Sons, Inc., New York, 1983), p. 315.
J. S. T. van Aswegen and R. W. K. Honeycombe, Acta Metall. 10, 262 (1962).
J. S. T. van Aswegen, R. W. K. Honeycombe, and D. H. Warrington, Acta Metall. 12, 1 (1964).
J.M. Silcock and W.J. Tunstall, Philos. Mag. 10, 361 (1964).
J. P. Shepherd, Metall. Sci. J. 3, 229 (1969).
G. Thomas and R.H. Willens, Acta Metall. 12, 191 (1968).
H. Nordberg and B. Aaronson, J. Iron Steel Inst. 206, 263 (1968).
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Han, K.H., Lee, H.E. A microstructural study of rapidly solidified and heat-treated austenitic Fe–Mn−Al–Mo–W–Nb–C alloys. Journal of Materials Research 10, 1371–1378 (1995). https://doi.org/10.1557/JMR.1995.1371
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DOI: https://doi.org/10.1557/JMR.1995.1371