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The role of defects during precipitate growth in a Ni-45wt% Cr alloy

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dc.contributor.authorChen, Jhewn-Kuangen
dc.contributor.committeechairReynolds, William T. Jr.en
dc.contributor.committeememberDesu, Seshu B.en
dc.contributor.committeememberFarkas, Dianaen
dc.contributor.committeememberGibbs, Gerald V.en
dc.contributor.committeememberHowe, J. M.en
dc.contributor.committeememberKampe, Stephen L.en
dc.contributor.departmentMaterials Engineering Scienceen
dc.date.accessioned2014-03-14T21:13:09Zen
dc.date.adate2008-06-06en
dc.date.available2014-03-14T21:13:09Zen
dc.date.issued1995-09-17en
dc.date.rdate2008-06-06en
dc.date.sdate2008-06-06en
dc.description.abstractThe defect structure, atomic structure, and energy of the interphase boundaries between an fcc matrix and a lath-shaped bcc precipitate in Ni-45 wt% Cr were investigated. The interfacial structure on the side facet of the precipitate consists of regular structural ledges and misfit dislocations. No regular defect structure can be found on the habit plane, or broad face, of the lath except for atomic-scale structural ledges. High resolution electron microscopy (HREM) observations show the (12¯1)<sub>f</sub> habit plane is coherent and is a good matching interface. Based upon conventional transmission electron microscopy (TEM) observations, the orientation of the habit plane results from advancing growth ledges on the conjugate plane of the Kurdjumov-Sachs orientation relationship. Using embedded atom method (EAM) simulations, the interfacial energy of the (12¯1)<sub>f</sub> habit plane is calculated and the simulated interphase structure is compared with the HREM observations. The simulated interface represents a major portion of the observed interface. The calculated interfacial energy of the (12¯1)<sub>f</sub> habit plane is 210 mJ/m², lower than typical grain boundary energies indicating this habit plane is a low-energy interphase boundary. A non-Bain lattice correspondence is identified and employed to predict the (12¯1)<sub>f</sub> habit plane successfully, although a Bain correspondence is more successful at predicting the elongation direction for the precipitate. Geometric matching is proposed to be responsible for determining the orientation of the precipitate habit plane and the growth direction. Lattice correspondence-based approaches such as the invariant line model and the phenomenological theory of martensitic crystallography can mimic aspects of geometric matching, but they do not accurately reflect the transformation mechanism during precipitation of bcc laths from an fcc parent.en
dc.description.degreePh. D.en
dc.format.extentxiii, 158 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-06062008-162241en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-06062008-162241/en
dc.identifier.urihttp://hdl.handle.net/10919/38172en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1995.C445.pdfen
dc.relation.isformatofOCLC# 34398118en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjecthabit planeen
dc.subjectlattice correspondenceen
dc.subjectinterfacial structureen
dc.subjectprecipitate morphologyen
dc.subjectatomic matchingen
dc.subject.lccLD5655.V856 1995.C445en
dc.titleThe role of defects during precipitate growth in a Ni-45wt% Cr alloyen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineMaterials Engineering Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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