The fatigue life of a complex microstructure with bainite in a high carbon Cr-Si tool steel
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1. J. Rieu and C. Goux: Mere. Sci. Rev. Metall., 1969, vol. 65, pp. 869-80. 2. D. Pads and P. Lesbats: J. Nucl. Mater., 1978, vol. 69, pp. 628-32. 3. J.P. Rivi/:re, H. Zonon, and J. Grilh6: Phys. Status Solidi A, 1973, vol. 16, pp. 545-52. 4. D. Weber, M. Meurtin, D. Paris, A. Fourdeux, and P. Lesbats: J. Phys. C7, 1977, vol. 38, pp. 332-36. 5. A. Fourdeux and P. Lesbats: Phil. Mag., 1982, vol. 45, pp. 81-93. 6. A. Ball and R.E. Smallman: Acta Metall., 1968, vol. 16, pp. 233-41. 7. J.E. Eibner, H.J. Engell, H. Schultz, H. Jacobi, and G. Schlatte: Phil. Mag. A, 1975, vol. 31, pp. 739-42. 8. A. Parthasarthi and H.L. Fraser: Phil. Mag. A, 1984, vol. 50, pp. 89-100. 9. P.R. Munroe and I. Baker: Scripta Metall., 1989, vol. 23, pp. 495-99. 10. P.R. Munroe and I. Baker: J. Mater. Sci., 1989, vol. 24, pp. 4246-52. 11. I. Baker, P. Nagpal, F. Liu, and P. Munroe: Acta Metall., unpublished research. 12. J.H. Westbrook: J. Electrochem. Soc., 1956, vol. 127, pp. 54-63. 13. B. Schmidt, P. Nagpal, and I. Baker: Proc. MRS, 1989, vol. 133, pp. 755-60.
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at. %AI Fig. 2 - - G r a p h of microhardness vs at. pct AI for NiAI after various heat treatments.
between water-quenched samples and samples given a low-temperature anneal is much less than in FeA1. Stoichiometric NiA1 showed the largest increase in hardness due to retained vacancies from water-quenching; however, even in this composition, the hardness increase due to air cooling was small compared to FeA1. Thus, it appears that differences in cooling rate can have dramatic effects on the hardness of FeAI but much lesser effects on the hardness of NiAI. Previously, retained vacancies after air-cooling have been shown to produce substantial increases in room-temperature yield strength and decreases in ductility in FeA1. ~13]The present study shows that even after slowly (furnace) cooling FeA1, retained vacancies can increase room-temperature hardness and, presumably, yield strength. The implication of these results is that previous reports of the lowtemperature strength of FeA1 need to be treated with caution. Different, nonquench, cooling rates can produce changes in strength of up to 80 pct which may be more than grain size strengthening effects in this material. It is clear that to measure room-temperature properties that are not influenced by thermal vacancy retention, FeA1 has to be annealed at a low temperature, -673 K, for around 100 hours.
The authors gratefully acknowledge Dr. F.D. Lemkey of the United Technologies Research Center for providing the ingots and Mr. D.J. Gaydosh and Drs. J.D. Whittenberger and M.V. Nathal of the NASA-Lewis Research Center, for extruding them. This work was supported by the United States Department of Energy, Office of Basic Energy Sciences, through Contract No. DE-FG02-87ER45311. 2282 - - VOLUME 21A, AUGUST 1990
The Fatigue Life of a Complex Microstructure with Bainite in a High Carbon Cr-Si Tool Steel
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