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dc.contributor.supervisorDeng, Chuang (Mechanical Engineering)en_US
dc.contributor.authorAramfard, Mohammad
dc.date.accessioned2015-12-01T16:35:45Z
dc.date.available2015-12-01T16:35:45Z
dc.date.issued2015
dc.identifier.urihttp://hdl.handle.net/1993/30957
dc.description.abstractNanocrystalline (NC) metals with averaged grain size smaller than 100 nm have shown promising mechanical properties such as higher hardness and toughness than conventional coarse-grained metals. Unlike conventional metals in which the deformation is controlled by dislocation activities, the microstructural evolution in NC metals is mainly dominated by grain rotation and stress-driven grain boundary motion (SDGBM) due to the high density of grain boundaries (GBs). SDGBM is thus among the most studied modes of microstructural evolution in NC materials with particular interests on their fundamental atomistic mechanisms. In the first part of this thesis, molecular dynamics simulations were used to investigate the influences of Triple Junctions (TJs) on SDGBM of symmetric tilt GBs in copper by considering a honeycomb NC model. TJs exhibited asymmetric pinning effects to the GB migration and the constraints by the TJs and neighboring grains led to remarkable non-linear GB motion in directions both parallel and normal to the applied shear. Based on these findings, a generalized model for SDGBM in NC Cu was proposed. In the second part, the interaction of SDGBM with crack, voids and precipitates was investigated. It was found that depending on the GB structure, material type and temperature, there is a competition between different atomistic mechanisms such as crack healing, recrystallization and GB decohesion. It is hoped that the findings of this work could clarify the micro-mechanisms of various experimental phenomena such as grain refinement in metals during severe plastic deformation, which can be used to design optimized route of making stabilized bulk NC metals.en_US
dc.language.isoengen_US
dc.rightsinfo:eu-repo/semantics/openAccess
dc.subjectMD, nanocrystalline metals, shear coupling, triple junction, grain boundary motion, cracken_US
dc.titleInfluences of stress-driven grain boundary motion on microstructural evolution in nanocrystalline metalsen_US
dc.typeinfo:eu-repo/semantics/masterThesis
dc.typemaster thesisen_US
dc.degree.disciplineMechanical Engineeringen_US
dc.contributor.examiningcommitteeWu, Nan (Mechanical Engineering) Hu, Can-Ming (Physics and Astronomy)en_US
dc.degree.levelMaster of Science (M.Sc.)en_US
dc.description.noteFebruary 2016en_US


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