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Intrinsic fatigue crack propagation in aluminum-lithium alloys - The effect of gaseous environmentsGaseous environmental effects on intrinsic fatigue crack growth are significant for the Al-Li-Cu alloy 2090, peak aged. For both moderate Delta K-low R and low Delta K-high R regimes, crack growth rates decrease according to the environment order: purified water vapor, moist air, helium and oxygen. Gaseous environmental effects are pronounced near threshold and are not closure dominated. Here, embrittlement by low levels of H2O (ppm) supports hydrogen embrittlement and suggests that molecular transport controlled cracking, established for high Delta K-low R, is modified near threshold. Localized crack tip reaction sites or high R crack opening shape may enable the strong, environmental effect at low levels of Delta K. Similar crack growth in He and O2 eliminates the contribution of surface films to fatigue damage in alloy 2090. While 2090 and 7075 exhibit similar environmental trends, the Al-Li-Cu alloy is more resistant to intrinsic corrosion fatigue crack growth.
Document ID
19900054273
Document Type
Conference Paper
Authors
Piascik, Robert S. (Virginia Univ. Charlottesville, VA, United States)
Gangloff, Richard P. (Virginia, University Charlottesville, United States)
Date Acquired
August 14, 2013
Publication Date
January 1, 1989
Subject Category
METALLIC MATERIALS
Meeting Information
International Conference on Fracture (ICF7)(Houston, TX)
Funding Number(s)
CONTRACT_GRANT: NAG1-745
Distribution Limits
Public
Copyright
Other