Abstract/Details

Cryomilled Aluminum Stabilized by Diamondoid Nanoparticles


2011 2011

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Abstract (summary)

Nanocrystalline aluminum powder with an average grain size of 22nm was prepared via cryomilling. Hot Isostatic Pressing was used to consolidate the powder followed by hot extrusion to homogenize the consolidated material. The high homologous temperature processes tend to increase the average grain diameter beyond the nanoscle classification, which is less than 100 nm. Diamantane was added during cryomilling to enhance the thermal stability in nanocrystalline aluminum. The thermal stability test data show that aluminum reinforced with 1 wt% diamantane exhibit two to three fold better thermal stability than non-reinforced aluminum when annealed at 773K (0.84 Tm) for ten hours. A similar trend is shown for the samples consolidated at 693K. This finding is explained through Burke’s model for grain growth in materials containing secondary particles to inhibit grain boundary motion.

The mechanical properties of cryomilled aluminum stabilized by 0.5 wt% and 1 wt% diamantane particles are compared with cryomilled commercial purity (CP) aluminum with no diamantane after high strain rate deformation (trap extrusion). The grain size of cryomilled CP aluminum is 0.6 to 1.2 times larger than the samples containing diamantane. In contrast to Hall-petch predictions, cryomilled aluminum with diamantane has relatively lower flow stress while demonstrating a 2.7-3.7 time higher ductility compared to cryomilled CP aluminum. Possible reasons for this behavior are suggested in mechnical property section.

A combination of higher temperature and pressure resulted in formation of Aluminum tris (Al(C9H6NO)3) precipitates from diamantane in the cryomilled aluminum matrix. The precipitates were formed during trap extrusion process but only seen in samples containing 1 wt% diamantane and HIP’ed at 521°C. Therefore, the HIP'ng temperature plays an important role in formation of these precipitates.

Indexing (details)


Subject
Engineering;
Nanotechnology;
Materials science;
Studies;
Nanoparticles
Classification
0537: Engineering
0652: Nanotechnology
0794: Materials science
Identifier / keyword
Applied sciences; Aluminum; Cryomilling; Diamondoid; Grain size stability; Metal matrix composite; Nanocrystalline
Title
Cryomilled Aluminum Stabilized by Diamondoid Nanoparticles
Author
Maung, Khinlay
Number of pages
112
Publication year
2011
Degree date
2011
School code
0030
Source
DAI-B 72/12, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9781124885599
Advisor
Mohamed, Farghalli A.
Committee member
Earthman, James C.; Mecartney, Martha L.
University/institution
University of California, Irvine
Department
Materials Science and Engineering - Ph.D.
University location
United States -- California
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3473771
ProQuest document ID
896481559
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/896481559
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