A further determination of the austenite solidus of the Fe-C system
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Stimulating discussion with Dr. V. Sagar Dwivedi is acknowledged. We wish to thank Director (RDCIS) for approval to publish this work.
REFERENCES 1. A. P. Coldren, G. Tither, A. Cornford, and J. R. Hiam: Proc. Symp. on "Formable HSLA and Dual Phase Steel," A.T. Davenport, ed., TMSAIME, Warrendale, PA, 1979, pp. 205-26. 2. A.P. Coldren and G. Tither: J. Metals, April 1978, vol. 30, pp. 6-9. 3. T. Greday, H. Mathy, and P. Messien: Proc. Symposium on "Structure and Properties of Dual-Phase Steel," R. A. Kot and J. Morris, Jr., eds., TMS-A1ME, Warrendale, PA, 1980, pp. 260-80. 4. J.M. Rigsbee, J.K. Abraham, A.T. Davenport, J.E. Franklin, and J.M. Picken: ibid., pp. 304-29. 5. Y.E. Smith and C.A. Siebert: Metall. Trans., 1971, vol. 2, pp. 1171-75. 6. T. Furukawa, H. Morikawa, H. Takechi, and K. Koyama: Proc. Symposium on "Structure and Properties of Dual Phase Steels," R. A. Kot and J.W. Morris, Jr., eds., TMS-A1ME, Warrendale, PA, 1980, pp. 281-303. 7. T. Tanaka, N. Tabata, T. Hatomura, and C. Shiga: Proc. Symposium on High Strength Low-alloy Steels, "Microalloying 75," October 1-3, 1975, Editorial and Printing: John Crane, Union Carbide Corporation, Washington, DC, 1977.
A Further Determination of the Austenite Solidus of the Fe-C System
An additional characteristic of Chipman's solidus line which bears investigation is that it exhibits an inflection at approximately 1 wt pct C. This rather unusual construction resulted from the need to fit the line to the data from three separate investigations,3'4'5 and was the best compromise at that time. Accurate information on the Fe-C system is vital to solidification studies of cast irons and to 7 solidus determinations in commercially important ternary systems such as Fe-C-Cr, Fe-C-Si, and Fe-C-Mn. Further work to resolve these anomalies is obviously indicated. This communication reports the results of DTA determinations of high purity Fe-C alloys in the range 0.44 to 2.03 wt pct C. In the previous study, ~ since both liquidus and solidus temperatures were investigated for each alloy, the composition range was necessarily limited to C > 1.5 wt pct. In the current work, solidus temperatures alone were determined and it was therefore possible to examine a wider range of alloy compositions. Alloy preparation and purity, methods of chemical analysis, DTA experimental technique, and error analysis have already been fully described. ~Spectroscopic analysis of the samples indicated a low level of impurities, similar to that reported in the earlier study. Again, the start of the DTA peak on heating, after the specimen was homogenized for one hour at a temperature just below the solidus, was taken as representative of the commencement of the reaction 7---~ L + 7. Arrest temperatures, corrected for thermocouple response and drift, were then extrapolated to zero heating rate. The thermograms for the alloy Fe-2.03 wt pct C, which typify the results obtained for this range of compositions, are shown in Figure 1. The corresponding extrapolation of arrest temperatures is represented in F
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