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dc.contributor.advisorClarke, Kester
dc.contributor.advisorClarke, Amy
dc.contributor.authorKoike, Kenji
dc.date.accessioned2019-10-15T17:46:31Z
dc.date.accessioned2022-02-03T13:16:40Z
dc.date.available2020-10-07T17:46:33Z
dc.date.available2022-02-03T13:16:40Z
dc.date.issued2019
dc.identifierKoike_mines_0052N_11784.pdf
dc.identifierT 8802
dc.identifier.urihttps://hdl.handle.net/11124/173286
dc.descriptionIncludes bibliographical references.
dc.description2019 Fall.
dc.description.abstractCold-rolled Cu-Ti alloy sheets are commonly used as connectors for electronic devices, because of their excellent mechanical properties and formability relative to conventional commercial copper alloys. Cu-Ti alloy sheets having even higher strengths are highly desired to meet the demands of continued miniaturization of electronic devices. In order to achieve exceptional mechanical properties, severe plastic deformation (SPD) methods are of great interest, because they can produce ultra-fine grained materials with grain size less than 1 µm. This study investigated changes in microstructure and mechanical properties of Cu-Ti alloy sheets during heavy cold rolling and subsequent annealing to determine optimum process routes and conditions to attain excellent mechanical properties. Cu-Ti alloys with and without Cu-Ti precipitates in the matrix were prepared as the initial materials. Pre-existing Cu-Ti precipitates were plastically deformed and severely elongated in the rolling direction via cold rolling, accelerating the formation of a nano-lamellar structure. A mean lamellar boundary spacing of 20 nm was achieved at an equivalent strain of 6.7. Ultimate tensile strength, yield strength, and Vickers hardness increased with a decrease in the lamellar boundary spacing, following the Hall-Petch relationship. Therefore, the strength of heavily deformed Cu-Ti sheets can be primarily attributed to grain boundary strengthening related to the lamellar boundaries. Subsequent annealing after cold rolling clearly enhanced the mechanical properties, and a maximum Vickers hardness value of 443 HV (4.35 GPa) was attained in the sample with pre-existing precipitates rolled to a strain of 6.7. These results suggest that pre-existing precipitates promote microstructural refinement during heavy cold rolling, and heavily cold-rolled Cu-Ti alloys exhibit anneal hardening behavior, leading to excellent mechanical properties.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.rightsCopyright of the original work is retained by the author.
dc.subjectcopper titanium
dc.subjectmicrostructure
dc.subjectsevere plastic deformation
dc.subjectmechanical properties
dc.subjectcold rolling
dc.subjectprecipitates
dc.titleMicrostructural evolution and mechanical properties of heavily cold-rolled and subsequently annealed copper titanium alloys
dc.typeText
dc.contributor.committeememberFindley, Kip Owen
dc.contributor.committeememberField, Robert
dcterms.embargo.terms2020-10-07
dcterms.embargo.expires2020-10-07
thesis.degree.nameMaster of Science (M.S.)
thesis.degree.levelMasters
thesis.degree.disciplineMetallurgical and Materials Engineering
thesis.degree.grantorColorado School of Mines
dc.rights.accessEmbargo Expires: 10/07/2020


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