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Hydrogen effects on the point defect spectrum in Fe-C alloys

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dc.contributor.advisor Sidney Yip. en_US
dc.contributor.author Monasterio Velásquez, Paul Rene en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering. en_US
dc.date.accessioned 2009-03-16T19:40:41Z
dc.date.available 2009-03-16T19:40:41Z
dc.date.issued 2008 en_US
dc.identifier.uri http://hdl.handle.net/1721.1/44769
dc.description Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008. en_US
dc.description "May 2008." en_US
dc.description Includes bibliographical references (p. 60-62). en_US
dc.description.abstract As part of a multi-scale approach for modeling hydrogen embrittlement in hardened steels we have investigated, employing density functional theory methods, the stability and concentrations of the point defect clusters present in metastable Fe-C-H alloys with vacancies. The defect spectrum is found to be strongly dependent on the local vacancy concentration, and for low hydrogen levels sharp highly non-linear changes in the defect cluster population are observed at critical vacancy concentrations. This critical-like behavior suggests an energy activation mechanism which can be characterized by an effective defect-cluster formation energy barrier. By analogy with similar activated processes such as the liquid-to-glass transition in super-cooled liquids, we postulate that this criticality is associated with the presence of deep wells in the energy landscape where chemical composition plays the role of generalized coordinate. Increases in the hydrogen content have the qualitative effect of reducing the slopes in the defect concentrations. The drastic sensitivity of the defect cluster spectrum to local changes in vacancy and impurity concentrations implies that in proximity of surfaces and extended defects multiple defect clusters become statistically significant and migration dependent phenomena, such as creep-relevant to hydrogen embrittlement-and super-diffusion, should be controlled by multiple activation barriers. en_US
dc.description.statementofresponsibility by Paul Rene Monasterio Velásquez. en_US
dc.format.extent 62 p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.rights.uri http://dspace.mit.edu/handle/1721.1/7582 en_US
dc.subject Nuclear Science and Engineering. en_US
dc.title Hydrogen effects on the point defect spectrum in Fe-C alloys en_US
dc.type Thesis en_US
dc.description.degree S.M. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering. en_US
dc.identifier.oclc 300276757 en_US


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