Metallurgical Transactions A

, Volume 9, Issue 8, pp 1039–1053 | Cite as

Mechanisms of tempered martensite embrittlement in low alloy steels

  • R. M. Horn
  • Robert O. Ritchie
Mechanical Behavior


An investigation into the mechanisms of tempered martensite embrittlement (TME), also know as “500°F” or “350°C” or one-step temper embrittlement, has been made in commercial, ultra-high strength 4340 and Si-modified 4340 (300-M) alloy steels, with particular focus given to the role of interlath films of retained austenite. Studies were performed on the variation of i) strength and toughness, and ii) the morphology, volume fraction and thermal and mechanical stability of retained austenite, as a function of tempering temperature, following oil-quenching, isothermal holding, and continuous air cooling from the austenitizing temperature. TME was observed as a decrease in bothK Ic and Charpy V-notch impact energy after tempering around 300°C in 4340 and 425°C in 300-M, where the mechanisms of fracture were either interlath cleavage or largely transgranular cleavage. The embrittlement was found to be concurrent with the interlath precipitation of cementite during temperingand the consequent mechanical instability of interlath films of retained austenite during subsequent loading. The role of silicon in 300-M was seen to retard these processes and hence retard TME to higher tempering temperatures than for 4340. The magnitude of the embrittlement was found to be significantly greater in microstructures containing increasing volume fractions of retained austenite. Specifically, in 300-M the decrease inK Ic, due to TME, was a 5 MPa√m in oil quenched structures with less than 4 pct austenite, compared to a massive decrease of 70 MPa√m in slowly (air) cooled structures containing 25 pct austenite. A complete mechanism of tempered martensite embrittlement is proposed involving i) precipitation of interlath cementite due to partial thermal decomposition of interlath films of retained austenite, and ii) subsequent deformation-induced transformation on loading of remaining interlath austenite, destabilized by carbon depletion from carbide precipitation. The deterioration in toughness, associated with TME, is therefore ascribed to the embrittling effect of i) interlath cementite precipitates and ii) an interlath layer of mechanically-transformed austenite,i.e., untempered martensite. The presence of residual impurity elements in prior austenite grain boundaries, having segregated there during austenitization, may accentuate this process by providing an alternative weak path for fracture. The relative importance of these effects is discussed.


Austenite Metallurgical Transaction Cementite Lath Boundary Ductile Rupture 
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  1. 1.
    J. R. Low , Jr.: inFract. Eng. Mater., ASM, 1964, p. 127.Google Scholar
  2. 2.
    C. I. McMahon, Jr.: ASTM STP 407, p. 127, American Society for Testing and Materials, 1968.Google Scholar
  3. 3.
    E. B. Kula and A. A. Anctil:J. Mater., 1964, vol. 4, p. 817.Google Scholar
  4. 4.
    B. J. Schulz and C. J. McMahon, Jr.: ASTM STP 499, p. 104, American Society for Testing and Materials, 1972.Google Scholar
  5. 5.
    M. A. Grossmann:Trans. AIME, 1946, vol. 167, p. 39.Google Scholar
  6. 6.
    H. Schrader, H. J. Wiester, and H. Siepmann:Arch. Eisenhuettenw., 1950, vol. 21, p. 21.Google Scholar
  7. 7.
    R. L. Rickett and J. M. Hodge:Proc. ASTM, 1951, vol. 51, p. 931.Google Scholar
  8. 8.
    L. J. Klingler, W. J. Barnett, R. P. Frohmberg, and A. R. Troiano:Trans. ASM, 1954, vol. 46, p. 1557.Google Scholar
  9. 9.
    J. J. Irani, M. J. May, and D. Elliott: ASTM STP 407, p. 168, American Society for Testing and Materials, 1968.Google Scholar
  10. 10.
    E. J. Ripling:Trans. ASM, 1950, vol. 42, p. 439.Google Scholar
  11. 11.
    G. V. Luerssen and O. V. Greene:, 1935, vol. 23, p. 861.Google Scholar
  12. 12.
    L. S. Castleman, B. L. Averbach, and M. Cohen:, 1952, vol. 44, p. 240.Google Scholar
  13. 13.
    R. M. Horn: Ph.D. Thesis, University of California at Berkeley, 1976 (Lawrence Berkeley Laboratory Report No. LBL-5787, December 1976).Google Scholar
  14. 14.
    V. H. Lindborg and B. L. Averbach:Acta Met., 1966, vol. 14, p. 1583.CrossRefGoogle Scholar
  15. 15.
    E. F. Walker and M. J. May: ISI Publ. 120, p. 135, 1970.Google Scholar
  16. 16.
    W. Backfisch and K. H. Schwalbe:Proc. Fourth International Conf. on Fracture, Waterloo, vol. 2, p. 73, 1977.Google Scholar
  17. 17.
    J. E. King, R. F. Smith, and J. F. Knott:Ibid, vol. 2, p. 279.Google Scholar
  18. 18.
    G. Thomas:Met. Trans. A, 1978, vol. 9A, p. 439.CrossRefGoogle Scholar
  19. 19.
    A. Nakashima and J. F. Libsch:Trans. ASM, 1961, vol. 53, p. 753.Google Scholar
  20. 20.
    B. S. Lement, B. L. Averbach, and M. Cohen:, 1954, vol. 46, p. 851.Google Scholar
  21. 21.
    A. J. Baker, F. J. Lauta, and R. P. Wei: ASTM STP 370; p. 3, American Society for Testing and Materials, 1963.Google Scholar
  22. 22.
    R. D. Goolsby: Ph.D. Thesis, University of California in Berkeley, 1971 (Lawrence Berkeley Laboratory Report No. LBL-405, November 1971).Google Scholar
  23. 23.
    A. G. Allten and P. Payson:Trans. ASM, 1953, vol. 45, p. 498.Google Scholar
  24. 24.
    C. H. Shih, B. L. Averbach, and M. Cohen:, 1956, vol. 48, p. 86.Google Scholar
  25. 25.
    C. J. Altstetter, M. Cohen, and B. L. Averbach:, 1962, vol. 55, p. 287.Google Scholar
  26. 26.
    M. S. Bhat: Ph.D. Thesis, University of California at Berkeley, 1977 (Lawrence Berkeley Laboratory Report No. LBL-6046, February 1977)Google Scholar
  27. 27.
    W. S. Owen:J. Iron Steel Inst., 1957, vol. 177, p. 445.Google Scholar
  28. 28.
    B. R. Banerjee: ASTM STP 370, p. 94, American Society for Testing and Materials, 1963.Google Scholar
  29. 29.
    B. R. Banerjee:J. Iron Steel Inst., 1965, vol. 203, p. 166.Google Scholar
  30. 30.
    J. M. Capus and G. Mayer:Metallurgia, 1960, vol. 62, p. 133.Google Scholar
  31. 31.
    J. R. Rellick and C. J. McMahon, Jr.:Met. Trans., 1974, vol. 5, p. 2439.CrossRefGoogle Scholar
  32. 32.
    S. K. Banerji, C. J. M Mahon, Jr., and H. C. Feng:Met. Trans. A, 1978, vol. 9A, p. 237.CrossRefGoogle Scholar
  33. 33.
    R. M. Horn and R. O. Ritchie:Proc. 106th Annual AIME Meeting, Atlanta, March 1977.Google Scholar
  34. 34.
    F. J. Witt:Practical Application of Fracture Mechanics to Pressure-Vessel Technology, p. 163, The Institute of Mechanical Engineers, London, 1971.Google Scholar
  35. 35.
    J. D. Landes and J. A. Begley: Westinghouse Scientific Paper 76-1E7-JINTF-P3, May 1976, Westinghouse Research Laboratories, Pittsburgh, Pa. 15235.Google Scholar
  36. 36.
    R. O. Ritchie, G. G. Garrett, and J. F. Knott:Int. J. of Fract. Mech, 1971, vol. 7, p. 462.Google Scholar
  37. 37.
    B. D. Cullity: inElements of X-Ray Diffraction, p. 391, Addison-Wesley Publ. Co. Inc., Reading, Mass., 1959.Google Scholar
  38. 38.
    D. Bhandarkar, V. F. Zackay, and E. R. Parker:Met. Trans., 1972, vol. 3, p. 2619.CrossRefGoogle Scholar
  39. 39.
    R. O. Ritchie, M. H. Castro-Cedeno, V. F. Zackay, and E. R. Parker:Met. Trans. A, 1978, vol. 9A, p. 35.CrossRefGoogle Scholar
  40. 40.
    C. W. Marschall, R. F. Hehemann, and A. R. Troiano:Trans. ASM, 1962, vol. 55, p. 135.Google Scholar
  41. 41.
    J. McMahon and G. Thomas:Proc. Third Int’l Conf. on the Strength of Metals and Alloys, vol. 1, p. 180, Cambridge, Institute of Metals, London, August 1973.Google Scholar
  42. 42.
    G. Y. Lai, W. E. Wood, R. A. Clark, V. F. Zackay, and E. R. Parker:Met. Trans., 1974, vol. 5, p. 1663.CrossRefGoogle Scholar
  43. 43.
    B. V. N. Rao, J. Y. Koo, and G. Thomas:Proc. Electron Microscopy Society of America, p. 30, Claitors Publication Division, Baton Rouge, 1975.Google Scholar
  44. 44.
    K. J. Kim and L. H. Schwartz:Mater. Sci. Eng., in press.Google Scholar
  45. 45.
    W. W. Gerberich, P. L. Hemmings, V. F. Zackay, and E. R. Parker: inFracture 1969, p. 288, Proc. Second Int’l. Conf. on Fracture, Brighton, 1969, Chapman and Hall, Ltd., London.Google Scholar
  46. 46.
    R. O. Ritchie:J. Eng. Mater. Technol., Trans. ASME Series H, 1977, vol. 99, p. 195.Google Scholar
  47. 47.
    C. L. Briant and S. K. Banerji: Unpublished research, General Electric Co., Schenectady, New York, 1977.Google Scholar
  48. 48.
    R. O. Ritchie: Ph.D. Thesis, University of Cambridge, 1973.Google Scholar
  49. 49.
    G. Y. Lai, W. E. Wood, E. R. Parker, and V. F. Zackay: Lawrence Berkeley Laboratory Report No. LBL-2236, University of California, April, 1975.Google Scholar
  50. 50.
    Der-Hung Huang and G. Thomas:Met. Trans. A, 1977, vol. 8A, p. 1661.CrossRefGoogle Scholar

Copyright information

© American Society for Metals and The Metallurgical Society of AIME 1978

Authors and Affiliations

  • R. M. Horn
    • 1
  • Robert O. Ritchie
    • 2
  1. 1.Department of Materials Science and Mineral EngineeringUniversity of CaliforniaBerkeley
  2. 2.Department of Mechanical EngineeringMassachusetts Institute of TechnologyCambridge

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