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Controlling Deformability in Metallic Glass Nanopillars and Nanolattices

Citation

Liontas, Rachel (2017) Controlling Deformability in Metallic Glass Nanopillars and Nanolattices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9028PHX. http://resolver.caltech.edu/CaltechTHESIS:09132016-104159178

Abstract

Metallic glasses offer desirable mechanical properties, including high strength, hardness, and elasticity. In bulk, they suffer from catastrophic failure upon mechanical loads. However, ductility may emerge upon (1) reducing the characteristic dimension of the metallic glass to the nanoscale or (2) irradiating the metallic glass. These two methods of controlling metallic glass deformability are investigated through a host of mechanical experiments on metallic glass nanopillars and nanolattices before and after irradiation. The mechanical experiments are conducted inside a scanning electron microscope to allow simultaneous mechanical loading and visualization of nanoscale deformation behavior.

Such experiments reveal that helium irradiation of electrodeposited Ni73P27 metallic glass tensile nanopillars increases plasticity by a factor of two with no sacrifice in strength. Other tensile experiments on Zr-Ni-Al metallic glass nanopillars in as-sputtered and annealed states reveal substantial ductility, highly dependent upon both the nanopillar size and processing conditions. Molecular dynamics simulations, transmission electron microscopy, and synchrotron x-ray diffraction are used to explain the observed mechanical behavior through changes in free volume and short-range order.

Larger nanolattice structures are fabricated to contain hollow beams of metallic glass, with beam wall thicknesses in the nanoscale size range that may allow proliferation of the beneficial “smaller is more ductile” size effect observed in metallic glass nanopillars. Compression experiments on Zr-Ni-Al metallic glass nanolattices reveal enhanced deformability as the nanolattice wall thickness is reduced and upon irradiation. This work points to metallic glass nanolattices as promising candidates for radiation-intensive applications and demonstrates that by fabricating the metallic glass in a nanolattice architecture the beneficial nanoscale size effect in deformability can be preserved.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:metallic glass; irradiation; size effect; ductility; nanomaterials; mechanics; cellular solids
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemical Engineering
Minor Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Greer, Julia R.
Group:Kavli Nanoscience Institute
Thesis Committee:
  • Brady, John F. (chair)
  • Johnson, William Lewis
  • Greer, Julia R.
  • Arnold, Frances Hamilton
Defense Date:6 September 2016
Funders:
Funding AgencyGrant Number
National Science Foundation Graduate Research FellowshipDGE-11444
U.S. Department of EnergyDE-SC0006599
NASA Space Technology Research Grants ProgramNNX12AQ49G
National Academies Keck Futures InitativeNAKFI ANT1
Record Number:CaltechTHESIS:09132016-104159178
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:09132016-104159178
DOI:10.7907/Z9028PHX
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/nl502074dDOIArticle adapted for Chapter 2
http://dx.doi.org/10.1016/j.actamat.2016.07.050DOIArticle adapted for Chapter 3
ORCID:
AuthorORCID
Liontas, Rachel0000-0001-9925-9466
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9924
Collection:CaltechTHESIS
Deposited By: Rachel Liontas
Deposited On:19 Sep 2016 21:37
Last Modified:24 Jan 2019 22:02

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