Abstract/Details

Controlling thermal stability in nanostructured materials


2010 2010

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Abstract (summary)

Lack of adequate thermal stability has precluded widespread application of nanostructured metals and alloys in structural systems. While approaches to address this problem have been developed, their application to date is mainly for alloy systems containing thermally-stable second-phase particles that retard thermally-driven boundary migration. The goal of the present study is to address the problem of thermal stability in single-component, nanostructured metal systems. A novel approach to stabilize boundary migration using special boundary configurations is proposed. By using high-purity copper as a model system, this approach is demonstrated through the enhanced stability afforded by a dense network of twin boundaries. The specific experiments and characterization include creation of a range of microstructures using machining-based severe plastic deformation (SPD), analysis of the microstructures using electron microscopy, hardness and differential scanning calorimetry, and estimation of the stored energy of cold work. Unique combinations of strengthening and stabilization in the case of heavily twinned microstructures are identified. It is shown that certain types of nano-scale twinned microstructures are thermally more stable and stronger than ultrafine-grained (UFG) microstructures comprised of high-angle boundaries. The process engineering of these special, twinned microstructures with enhanced stability is applicable to the creation of bulk forms. A stability ‘map’ is obtained for ultrafine-grained copper microstructures produced by SPD at strain rates of 1 to 103 s−1, strains of 1 to 7 and temperatures as low as cryogenic. Furthermore, SPD process conditions for creating sub-100 nm (nanocrystalline) copper microstructures comprised primarily of high-angle boundaries, as well as microstructures dominated by nano-scale twinning, are identified. The stability approach and insights developed herein are important for stabilization of single-component, nanostructured metal systems that have hitherto not had a practical approach to stabilization against thermal fields. They also offer insights into potential routes for improving the stability of multi-component nanostructured alloys.

Indexing (details)


Subject
Industrial engineering;
Nanotechnology
Classification
0546: Industrial engineering
0652: Nanotechnology
Identifier / keyword
Applied sciences; Boundary migration; High-purity copper; Metals; Nanostructure; Thermal stability
Title
Controlling thermal stability in nanostructured materials
Author
Saldana, Christopher J.
Number of pages
164
Publication year
2010
Degree date
2010
School code
0183
Source
DAI-B 72/05, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9781124529011
Advisor
Chandrasekar, Srinivasan; Compton, W. Dale
Committee member
Dayananda, Mysore A.; King, Alexander H.; Stach, Eric A.
University/institution
Purdue University
Department
Industrial Engineering
University location
United States -- Indiana
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3444771
ProQuest document ID
859201368
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/859201368
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