Interfacial structure of delta phase in Inconel 718 and the selection of precipitate habit planes

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dc.contributor.authorLiang, Qiangen
dc.contributor.committeechairReynolds, William T. Jr.en
dc.contributor.committeememberFarkas, Dianaen
dc.contributor.committeememberDesu, Seshu B.en
dc.contributor.committeememberCurtin, W. A. Jr.en
dc.contributor.committeememberKampe, Stephen L.en
dc.contributor.departmentMaterials Engineering Scienceen
dc.date.accessioned2014-03-14T21:10:56Zen
dc.date.adate2006-05-11en
dc.date.available2014-03-14T21:10:56Zen
dc.date.issued1996-08-15en
dc.date.rdate2006-05-11en
dc.date.sdate2006-05-11en
dc.description.abstractWe investigated the structure and defects associated with interphase boundaries between a γ (fcc) matrix and plate-shaped precipitates of the δ (orthorhombic) phase in Inconel 718. Based upon transmission electron microscopy (TEM) observations, the average habit plane was confirmed to be (111)<sub>γ</sub> which is consistent with previous reports. A parallel array of misfit dislocations with Burgers vector b=1/6[112̅]<sub>γ</sub>, (designated M1) are always observed lying along the [11̅0] direction. Another array of misfit dislocations appears in some regions of the interface with Burgers vector b=1/6[21̅1̅]<sub>γ</sub> (designated M2). These dislocations also lie along the [11̅0] direction. Irregular ledges were identified on the interface and are believed to contribute to the thickening of δ plates. Dislocations in the matrix were also characterized. Most matrix dislocations have a 1/2[1̅01]<sub>γ</sub> Burgers vector. The growth ledges in the habit plane of a single δ plate have a variety of effective Burgers vectors. A geometric matching approach based upon near-coincident sites was employed to explain the interfaces structure of interphase boundaries in Inconel 718, as well as fdc/bcc in Ni-45wt% Cr. In both cases, the conjugate plane is the plane with the highest areal density of near-coincident sites over a small region while the average habit plane is determined by the continuity of near-coincidence sites over a large area. The M1 interfacial dislocations in the γ/δ interface accommodate misfit in the habit plane whereas M2 dislocations do not and are probably a by-product of the dissociation of matrix dislocations. In the fcc/bcc system, the habit plane is not parallel to the conjugate plane and the partial dislocations associated with matrix stacking faults improve matching in the habit plane even though their Burgers vector lies out of this plane.en
dc.description.degreePh. D.en
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-05112006-154827en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05112006-154827/en
dc.identifier.urihttp://hdl.handle.net/10919/37775en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1996.L535.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectHabit planeen
dc.subjectconjugate planeen
dc.subjectcoincident sitesen
dc.subjectprecipitate morphologyen
dc.subject.lccLD5655.V856 1996.L535en
dc.titleInterfacial structure of delta phase in Inconel 718 and the selection of precipitate habit planesen
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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