2026-09-22T00:57:02Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/45307 2023-07-11 col_2142_5131 col_2142_14800 com_2142_5130 com_2142_14799 com_2142_234

Made available in DSpace on 2013-08-22T16:35:38Z (GMT). No. of bitstreams: 4 Ruizhi_Li.pdf: 2616507 bytes, checksum: dff899bcd8bac69b54dbea75d994edac (MD5) 0_Li_Ruizhi.docx: 28848935 bytes, checksum: 4c460173b168128b9fb90f0828607c49 (MD5) Li_Ruizhi.docx: 28848935 bytes, checksum: 4c460173b168128b9fb90f0828607c49 (MD5) license.txt: 4056 bytes, checksum: 19f968ce7895acd28238d55fe2269aff (MD5) http://hdl.handle.net/2142/45307 en Copyright 2013 Ruizhi Li Chew, Huck Beng Li, Ruizhi 2013-08-22T16:35:38Z 2013-08-22T16:35:38Z 2013-08 2013-08-22T16:35:38Z 2013-08 The exceptional mechanical properties of metallic nanolayers originate from the high density of nanoscale interfaces. However, conflicting observations in the relationship between mechanical properties and interlayer thicknesses, as well as discrepancies in measured strength between experiments and simulations, suggest that microstructural flaws play an essential role in the deformation behavior of actual metallic nanolayers. In this thesis, molecular dynamics simulations are used to uncover two distinct nanoscale plasticity mechanisms activated by the presence of micro-cracks and columnar grain boundaries in Cu/Ag nanolayers under tension. The first mechanism is deformation twinning, caused by emission of twinning partials from the micro-cracks and columnar grain boundaries. These deformation microtwins are transmitted across multiple Cu/Ag interlayers and facilitate the communication between spatially separated flaws. In addition, the intersections of microtwins on non-parallel slip planes produce formidable locks, which serve as stress concentration sites for incipient crack growth. The second mechanism is interlayer interface migration, which results in the morphological transition of initially planar Cu/Ag nanolayer to become wavy. This planar-to-wavy transition is driven by energetics, and is facilitated by dislocation climb along columnar grain boundaries. The above tensile-activated plasticity mechanisms are distinctly different from the strengthening mechanism associated with interface crossings of single dislocations under compression. Implications of these mechanisms to the ductility of metallic nanolayers, as well as the activation of novel nanoscale plastic recovery processes, are discussed. Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2013-07-18T18:16:12Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 6 Li_Ruizhi.pdf: 74639302 bytes, checksum: a39bffe36721eca8735122020464b89d (MD5) Li_Ruizhi.pdf: 74636428 bytes, checksum: 1248bd58c140f749de736d5d47e543ce (MD5) Li_Ruizhi.pdf: 74647197 bytes, checksum: a95b778f1955b3f74d0650108cbaeb34 (MD5) 0_Li_Ruizhi.docx: 28848935 bytes, checksum: 4c460173b168128b9fb90f0828607c49 (MD5) Li_Ruizhi.docx: 28848935 bytes, checksum: 4c460173b168128b9fb90f0828607c49 (MD5) Li_Ruizhi.pdf: 2616507 bytes, checksum: dff899bcd8bac69b54dbea75d994edac (MD5) Nanolayered metals flaws deformation twinning interface migration wavy interfaces molecular dynamics Defect mediated plasticity in Cu/Ag nanoscale multilayered metal composites: deformation twinning and wavy interface formation text Aerospace Engineering 1615 Aerospace Engineering 4048 University of Illinois at Urbana-Champaign Thesis M.S. MS: Aerospace Engr -UIUC 10KS4048MS