Doctoral Dissertations

Sixie Huang

Abstract

"The mechanical behavior of Metallic Nanolayered Composites (MNCs) is governed by their underlying microstructure. In this dissertation, the roles of the interlayer spacing (grain size, d) and the intralayer biphase spacing (layer thickness, h) on mechanical response of Cu/Nb MNCs are examined by Molecular Dynamics (MD) simulations. The study of the strength of MNCs show that small changes in both d and h play a profound role in the relative plastic contributions from grain boundary sliding and dislocation glide. The interplay of d and h leads to a very broad transition region from grain boundary sliding dominated flow, where the strength of the material is weak and insensitive to changes in h, to grain boundary dislocation emission and glide dominated flow, where the strength of the material is strong and sensitive to changes in h.

The study of the fracture behavior of MNCs shows that cracks in Cu and Nb layers may exhibit different propagation paths and distances under the same external loading. Interfaces can improve the fracture resistance of the Nb layer in Cu/Nb MNCs by providing mobile dislocation sources to generate the plastic strain at the crack tip necessary for crack blunting. Increasing the layer thickness can further enhance the fracture resistance of both Cu and Nb layers, since the critical stress for activating dislocation motion decreases with increasing the layer thickness. A novel atomistic-informed interface-dislocation dynamics (I-DD) model has been developed to study Metal-Ceramic Nanolayered Composites (MCNCs) based on the key deformation process and microstructure features revealed by MD simulations. The I-DD predicted results match well with the prior experimental results where both yield stress and strain hardening rate increase as the layer thickness decreases. This I-DD model shows great potential in predicting and optimizing the mechanical properties of MNCs"--Abstract, page iv.

Advisor(s)

Zhou, Caizhi

Committee Member(s)

O'Keefe, Matthew
Van Aken, David C.
Asle Zaeem, Mohsen
Du, Xiaoping

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Sponsor(s)

National Science Foundation (U.S.)
University of Missouri Research Board
Extreme Science and Engineering Discovery Environment
Missouri University of Science and Technology. Materials Research Center

Comments

This work was supported by the grants from NSF CAREER Award (CMMI-1652662).

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2019

Journal article titles appearing in thesis/dissertation

  • Nanograin size effects on the strength of biphase nanolayered composites
  • Fracture resistance of Cu/Nb metallic nanolayered composite
  • Effect of plastic incompatibility on the strain hardening behavior of Al-TiN nanolayered composites

Pagination

xv, 96 pages

Note about bibliography

Includes bibliographic references.

Rights

© 2019 Sixie Huang, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 11534

Electronic OCLC #

1105154857

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