Metallurgical Transactions

, Volume 5, Issue 7, pp 1663–1670 | Cite as

The effect of austenitizing temperature on the microstructure and mechanical properties of as-quenched 4340 steel

  • G. Y. Lai
  • W. E. Wood
  • R. A. Clark
  • V. F. Zackay
  • E. R. Parker


The effect of austenitizing temperature on both the plane strain fracture toughness,K IC , and the microstructure of AISI 4340 was studied. Austenitizing temperatures of 870 and 1200°C were employed. All specimens austenitized at 1200°C were furnace cooled from the higher austenitizing temperature and then oil quenched from 870°C. Transmission electron microscopy revealed an apparent large increase in the amount of retained austen-ite present in the specimens austenitized at the higher temperature. Austenitizing at 870°C resulted in virtually no retained austenite; only minor amounts were found sparsely scat-tered in those areas examined. A considerably altered microstructure was observed in specimens austenitized at 1200°C. Fairly continuous 100 to 200Å thick films of retained austenite were observed between the martensite laths throughout most of the area exam-ined. Additionally, specimens austenitized at 870°C contained twinned martensite plates while those austenitized at 1200°C showed no twinning. Plane strain fracture toughness measurements exhibited an approximate 80 pct increase in toughness for specimens austen-itized at 1200°C compared to those austenitized at 870°C. The yield strength was unaffected by austenitizing temperature. The possible role of retained austenite and the elimination of twinned martensite in the enhancement of the fracture toughness of those specimens austen-itized at the higher temperature will be discussed.


Austenite Martensite Fracture Toughness Bainite Metallurgical Transaction Volume 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    V. F. Zackay, E. R. Parker, R. D. Goolsby, and W. E. Wood:NaturePhys. Sci., 1972, vol. 236(68), p. 108.Google Scholar
  2. 2.
    D. Huang and G. Thomas:Met. Trans., 1971, vol. 2, p. 1587.Google Scholar
  3. 3.
    R. Clark: M.S. Thesis, University of California, Berkeley, California, 1973, LBL-1801.Google Scholar
  4. 4.
    W. W. Gerberich and J. P. Birat:Int. J. Fract. Mech., 1971, vol. 7, p. 108.Google Scholar
  5. 5.
    S. D. Antolovich and B. Singh:Met. Trans., 1971, vol. 2, p. 2135.Google Scholar
  6. 6.
    Annual Book of ASTM Standards (American Society for Testing and Ma- terials), Philadelphia, 1971, vol. 31, p. 911.Google Scholar
  7. 7.
    J. E. Srawley and B. Gross:Mater. Res. Stand., 1967, vol. 7, p. 155.Google Scholar
  8. 8.
    J. R. Low, Jr.:Eng. Fract. Mech., 1968, vol. 1, p. 47.CrossRefGoogle Scholar
  9. 9.
    O. Johari and G. Thomas:Trans. ASM, 1965, vol. 58, p. 563.Google Scholar
  10. 10.
    J. A. McMahon and G. Thomas: “Development of Economical, Tough, Ultra- High-Strength Fe-Cr-C Steels,” LBL-1490, April 1973.Google Scholar
  11. 11.
    P. M. Kelly and J. Nutting:J. Iron Steel Inst, 1961,vol. 197, p. 199.Google Scholar
  12. 12.
    M. Bevis, P. C. Rowlands, and A. F. Acton:Trans. TMS-AIME, 1968, vol. 242, p. 1555.Google Scholar
  13. 13.
    G. Krauss and W. Pitsch:Acta Met., 1964, vol. 12, p. 278.CrossRefGoogle Scholar
  14. 14.
    A. Gilbert, G. T. Hahn, C. N. Reid, and B. A. Wilcox:Acta Met, 1964, vol. 12, p. 754.CrossRefGoogle Scholar
  15. 15.
    D. Webster:Tram. ASM, 1968, vol. 61, p. 816.Google Scholar
  16. 16.
    D. Webster:Met. Trans., 1971, vol. 2, p. 1857.Google Scholar
  17. 17.
    D. Webster:Met. Trans., 1971, vol. 2, p. 2097.Google Scholar
  18. 18.
    P. Babu: unpublished results, University of California, Berkeley, California.Google Scholar
  19. 19.
    E. M. Breinan and G. S. Ansell:Met. Trans., 1970, vol. 1, p. 1513.CrossRefGoogle Scholar
  20. 20.
    R. O. Ritchie, J. F. Knott, and L. C. E. Geniets: Third Intl. Conf. on the Strength of Metals and Alloys, Cambridge, England, 124, August 1973.Google Scholar

Copyright information

© American Society for Metals, The Melallurgical Society of AIME 1974

Authors and Affiliations

  • G. Y. Lai
    • 1
  • W. E. Wood
    • 2
  • R. A. Clark
    • 1
  • V. F. Zackay
    • 1
  • E. R. Parker
    • 1
  1. 1.University of CaliforniaBerkeley
  2. 2.Oregon Graduate CenterPortland

Personalised recommendations