Metallurgical Transactions A

, Volume 19, Issue 7, pp 1739–1750 | Cite as

Chemical and metallurgical aspects of environmentally assisted fatigue crack growth in 7075-T651 aluminum alloy

  • Ming Gao
  • R. P. Wei
  • P. S. Pao


A comprehensive study has been carried out on a 7075-T651 alloy to examine the influence of water vapor on fatigue crack growth. The kinetics of fatigue crack growth were determined as a function of water vapor pressure at room temperature and at 353 K. Detailed fractographic analyses and surface chemistry studies were carried out to identify the micromechanisms and to quantify the chemical interactions for corrosion fatigue crack growth in this alloy. Experiments were also carried out in ultra-high vacuum and in oxygen to provide for comparisons. Two regions of fatigue crack growth response were identified. In the low pressure region (below 67 Pa at 5 Hz), crack growth is controlled by the rate of transport of water vapor to the crack tip, and the response can be described by a model for transport controlled crack growth. At pressures above 67 Pa, additional increases in crack growth rate occurred, which are attributed to the further reactions of water vapor with segregated magnesium in this alloy. Different micromechanisms for crack growth have been identified for vacuum, oxygen, and water vapor. These micromechanisms are considered in relation to the environmental parameters through a modified superposition model for corrosion fatigue.


Metallurgical Transaction Crack Growth Rate Fatigue Crack Growth Fatigue Crack Growth Rate Water Vapor Pressure 
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  1. 1.
    R.P. Wei, P.S. Pao, R.G. Hart, T.W. Weir, and G.W. Simmons:Metall. Trans. A, 1980, vol. 11A, pp. 151–58.Google Scholar
  2. 2.
    T.H. Shih and R.P. Wei:Engr. Fract. Mech., 1983, vol. 18, pp. 827–37.CrossRefGoogle Scholar
  3. 3.
    T.W. Weir, G.W. Simmons, R.G. Hart, and R.P. Wei:Scripta Metall, 1980, vol. 14, pp. 357–64.CrossRefGoogle Scholar
  4. 4.
    R.P. Wei and G.W. Simmons:Intl. J. Fract. Mech., 1981, vol. 17, pp. 235–47.CrossRefGoogle Scholar
  5. 5.
    R.P. Wei and G.W. Simmons: in FATIGUE:Environment and Temperature Effects, John J. Burke and Volker Weiss, eds., Sagamore Army Materials Research Conference Proceedings, 1983, vol. 27, pp. 59-70.Google Scholar
  6. 6.
    R. Brazill, G. W. Simmons, and R. P. Wei:J. Engr. Math. & Tech., 1979, vol. 101, pp. 199–204.CrossRefGoogle Scholar
  7. 7.
    P. S. Pao, W. Wei, and R. P. Wei: inEnvironment-Sensitive Fracture of Engineering Materials, Z. A. Foroulis, ed., TMS-AIME, 1979, pp. 565-80.Google Scholar
  8. 8.
    F.J. Bradshaw and C. Wheeler:Intl. J. Fract. Mech., 1969, vol. 5, pp. 255–68.Google Scholar
  9. 9.
    A. Hartman, F. J. Jacobs, A. Nederveen, and R. DeRijk: NLR Tech. Note No. M2181, National Aerospace Laboratory, Amsterdam, The Netherlands, 1967.Google Scholar
  10. 10.
    ASTM E647-81, Standard Test Method for Constant-Load Amplitude Fatigue Crack Growth Rates Above 10−8m/cycle.Google Scholar
  11. 11.
    H.H. Johnson:Mater. Res. Stand., 1965, vol. 5, pp. 442–45.Google Scholar
  12. 12.
    Che-Yu Li and R.P. Wei:Mater. Res. Stand., 1966, vol. 6, pp. 392–94.Google Scholar
  13. 13.
    R. P. Wei and R. L. Brazill: inFatigue Crack Growth Measurement and Data Analysis, ASTM STP 738, S.J. Hudak and R.J. Bucci, eds., Am. Soc. Testing Mater., 1981, pp. 103-19.Google Scholar
  14. 14.
    R. M. N. Pelloux:Trans. Am. Soc. Metals, 1969, vol. 62, pp. 281–85.Google Scholar
  15. 15.
    W.G.C ark, Jr. and S.J. Hudak,Jr. :J. Testing Eval., 1975, vol. 3, pp. 454–76.Google Scholar
  16. 16.
    R. P. Wei, W. Wei, and G. A. Miller:J. Testing Eval., 1979, vol. 7, pp. 90–95.CrossRefGoogle Scholar
  17. 17.
    Dennis L. Dicus: in Environment-Sensitive Fracture, ASTM STP 821, S. W. Dean, E.N. Pugh, and G.M. Ugiansky, eds.,Am. Soc. Testing Mater., 1984, pp. 513-33.Google Scholar
  18. 18.
    R. P. Wei, Ming Gao, and P. S. Pao:Scripta Metall., 1984, vol. 18, pp. 1195–98.CrossRefGoogle Scholar
  19. 19.
    Ming Gao, P.S. Pao, and R.P. Wei: inFracture: Interactions of Microstructure, Mechanisms and Mechanics, J. M. Wells and J. D. Landes, eds., The Metallurgical Soc. of AIME, Warrendale, PA 15086, 1985, pp. 303–19.Google Scholar
  20. 20.
    J. Lankford and D.L. Davidson:Acta Metall., 1983, pp. 1273-84.Google Scholar
  21. 21.
    B. Tomkins and W. D. Biggs:J. Mater. Sci., 1969, vol. 4, pp. 544–53.CrossRefGoogle Scholar
  22. 22.
    C. Q. Bowles and J. Schijve: inFatigue Mechanisms: Advances in Quantitative Measurements of Physical Damage, ASTM STP 811, J. Lankford, D.L. Davidson, W.L. Morris, and R.P. Wei, eds., Am. Soc. Testing Mater., 1983, pp. 400-26.Google Scholar
  23. 23.
    K.J. Nix and H.M. Flower:Acta Metall, 1982, vol. 30, pp. 1549–59.CrossRefGoogle Scholar
  24. 24.
    R. P. Wei and P. S. Pao: Technical Report No. 2, Air Force Office of Scientific Research, 1983.Google Scholar
  25. 25.
    C.Q. Bowles and D. Broek:Intl. J. Fract. Mech., 1972, vol. 8, pp. 75–85.CrossRefGoogle Scholar
  26. 26.
    L.E. Davis, N.C. MacDonald, P.W. Palmberg, G.E. Riach, and R. E. Weber:Handbook of Auger Spectroscopy, Physical Electronics Industries, Inc., 1976.Google Scholar
  27. 27.
    R. P. Wei: inFatigue Mechanisms, ASTM STP 675, J. T. Fong, ed., Am. Soc. Testing Mater., 1979, pp. 816-40.Google Scholar
  28. 28.
    R.P. Wei: 21-24 Oct., 1985, Xi’an, People’s Republic of China, E.M.A.S., Warley, England.Google Scholar
  29. 29.
    R. P. Wei and Ming Gao:Scripta Metall., 1983, vol. 17, pp. 959–62.CrossRefGoogle Scholar
  30. 30.
    J.C. Fuggle, L.M. Watson, D.J. Fabian, and S. Affrossman:Surf. Sci., 1975, vol. 49, pp. 61–76.CrossRefGoogle Scholar

Copyright information

© The Metallurgical of Society of AIME 1988

Authors and Affiliations

  • Ming Gao
    • 1
  • R. P. Wei
    • 1
  • P. S. Pao
    • 2
  1. 1.Department of Mechanical Engineering and MechanicsLehigh UniversityBethlehem
  2. 2.Mechanics of Materials BranchNaval Research LaboratoryWashington, DC

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