Doctoral Dissertations

Abstract

"Metallic glass alloys possess superior corrosion resistance in comparison with the crystalline state of the same alloy due to their chemical and non-crystalline structural homogeneity. The high critical quenching rate required for synthesizing metallic glass alloys demands innovative engineering solutions to allow the commercial production of metallic glass alloys as structural materials.

The purpose of this research is to produce aluminum-based amorphous metallic coatings on aluminum alloy plates using an atmospheric plasma spray (APS) technique to form the corrosion resistant barrier coating. The corrosion resistance of APS coatings tested in a neutral salt-fog chamber showed that the coating performance was dependent on the crystallinity, coating permeability and composition.

The microstructures of the coating produced with the alloy with the highest glass forming ability, Al85Y8Ni5CO2 exhibited mixtures of amorphous and nanocrystalline α-Al particles. A combination of calorimetric and morphological investigations, using melt- spun ribbons with different compositions and quench rates, revealed the presence of yttrium-lean Al85+xY8-xNi5CO2 (x > 0) type amorphous phases, and such investigations explained the nucleation of nanocrystalline α-Al particles during the APS process. The chemical inhomogeneity of the APS coating originated from the local chemical distribution of the milled powder, insufficient plasma energy input and different powder flight paths within the plasma stream. However, the presence of multi-compositional amorphous phases with the associated morphologies of nanocrystalline α-Al particles hinted at significance of atomic clustering upon forming the amorphous phase"--Abstract, page iii.

Advisor(s)

Van Aken, David C.
Miller, F. Scott, 1956-

Committee Member(s)

O'Keefe, Matthew
Hilmas, Greg
Schuman, Thomas P.

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Publisher

University of Missouri--Rolla

Publication Date

Fall 2005

Journal article titles appearing in thesis/dissertation

  • Salt fog corrosion testing of Al-Y-Co based nanocrystalline and amorphous coatings produced by atmospheric plasma spray
  • Aluminum-based nanocrystalline coatings produced by atmospheric plasma spray
  • Microstructural analysis of plasma sprayed Al-based amorphous alloys: A comparison with melt-spinning technique

Pagination

xvii, 107 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2005 Yoshihide Kato, All rights reserved.

Document Type

Dissertation - Restricted Access

File Type

text

Language

English

Subject Headings

Plasma sprayingMetallic glassesGlass-ceramicsMelt spinningCrystallization -- Industrial applicationsAmorphous substancesAlloys

Thesis Number

T 8831

Print OCLC #

68810561

Electronic OCLC #

1088728510

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