Type
Text
Type
Dissertation
Advisor
Trelewicz, Jason | Venkatesh, T. | Gersappe, Dilip. | Tucker, Garritt.
Date
2017-08-01
Keywords
Crystalline-amorphous Nanolaminates | Materials science | Electrodeposition of Ni-W Nanolaminates | Instrumental Nanoindentation | Interface Mediated Deformation Behavior | Metallic Nanoglasses | Molecular Dynamics Simulations
Department
Department of Materials Science and Engineering.
Language
en_US
Source
This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree
Identifier
http://hdl.handle.net/11401/78327
Publisher
The Graduate School, Stony Brook University: Stony Brook, NY.
Format
application/pdf
Abstract
The unique mechanical behaviors of metallic crystalline-amorphous nanolaminates and nanoglasses have attracted great interests in recent years because of their remarkable strength and excellent plasticity. The presence of amorphous-crystalline interfaces(ACIs) or glass-glass interfaces(GGIs) significantly affected the deformation behaviors of these metallic nanostructures demonstrated by a number of experimental and computational studies. However, due to limitations in the experimental characterization and simulation methods, the underlying deformation mechanisms remain elusive. In this thesis, molecular dynamics simulations and instrumental nanoindentation were employed to probe the intriguing interface mediated deformation mechanisms. Starting with the simulated deformation of a novel columnar crystalline-amorphous nanolaminate model, the mechanistic coupling of dislocation and shear transformation zone(STZ) plasticity were captured at the ACI using the continuum deformation metrics, which provides an effective pathway for accommodating strain while circumventing the formation of deleterious grain boundary voids and primary shear bands. Then, through systematically varying the layer thickness and nanocrystalline grain size of nanolaminates, illustrative compound mechanics maps together with a properties map were constructed to unveil the relationship between microstructural length scales and mechanical behaviors and establish the mechanics-driven design principles for optimizing the performance of nanolaminates. These simulation results motivated the experimental study of electrodeposition synthesized Ni-W grain size modulated nanolaminates consisting of glass-like and nanocrystalline layers characterized by electron microscopy. Nanoindentation testing was performed to evaluate the mechanical behaviors of Ni-W nanolaminates with different layer thickness ratio emphasizing on the hardness and strain rate sensitivity. The interface mediated deformation mechanisms in the nanoglasses also greatly improves their mechanical performance. In the second half of this thesis, an original method was developed to identify the interface region of the nanoglass models generated by the simulated consolidation of glassy spheres and disclosed the unique interface properties, which were used to understand the deformation behaviors of nanoglasses with different annealing states and grain sizes. It was found out that the strain was evenly distributed to the interface in the nanoglasses inhibiting severe shear localization and it is thermal annealing instead of grain size that was more effective to tune the mechanical performance of nanoglasses. | 172 pages
Recommended Citation
Cheng, Bin, "Interface Mediated Deformation Behavior in Metallic Nanostructures" (2017). Stony Brook Theses and Dissertations Collection, 2006-2020 (closed to submissions). 3821.
https://commons.library.stonybrook.edu/stony-brook-theses-and-dissertations-collection/3821