The necessity of both plasticity and brittleness in the fracture thresholds of iron

W. W. Gerberich, R. A. Oriani, M. J. Lji, X. Chen, T. Foecke

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In order to explain discontinuous brittle cracking in materials subjected to hydrogen, single-crystal and crack/dislocation simulation studies have been made. The computational scheme allows the local stress tensor near a crack in an anisotropic elastic solid with shielding dislocations to be determined. The model system is iron with a load axis perpendicular to the {100} cleavage plane, growth in the macroscopic ⟨010⟩ direction, and an applied stress intensity of 16 M Pa m1/2. The result is that the elastic stress distribution is translated out from the crack tip by about 23 nm and that large stresses, although not of a singular nature, still exist. These stresses near 20 000 M Pa are sufficient to concentrate dilute solutions of hydrogen to nearly one hydrogen for every iron atom. Such stresses, combined with these extremely high hydrogen concentrations are proposed for the initiation of decohesion which grows locally over 1 μm size areas, as observed experimentally.

Original languageEnglish (US)
Pages (from-to)363-376
Number of pages14
JournalPhilosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties
Issue number2
StatePublished - Feb 1991

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS The authors would like to thank Dr R. Thomson of the National Institute of Technology and Standards for helpful discussions. This work was supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Science Division under Grant DE-FG02-84ER45141 and the Corrosion Center, Basic Energy Sciences Grant DE-FG02-88ER45337a nd the NSF Research Center for Interfacial Engineering Grant NSF/CDR-8721 551 .

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