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Icosahedral order in metastable metallic alloys

Citation

Anlage, Steven Mark (1988) Icosahedral order in metastable metallic alloys. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:09272010-145542274

Abstract

We examine the consequences of short-range icosahedral order in metastable metallic alloys. There is evidence, both direct and indirect, for the existence of atomic clustering with icosahedral symmetry in supercooled liquid metals, metastable metallic alloys, and large-unit-cell intermetallic compounds. It is observed that a variety of metallic alloys can exhibit a long-range ordered structure with icosahedral point group symmetry upon rapid quenching from the liquid. We have carefully examined one of these icosahedral phase-forming systems in an effort to understand how the long-range ordered solid develops from the liquid phase. Our studies show that the icosahedral phase nucleates homogeneously from the liquid during the rapid quenching process. We have developed a theory to explain qualitatively this observation. A model material is proposed, which is endowed with short-range icosahedral order broken up by defect structures. The thermodynamics of this model are described by a Ginzburg-Landau theory. The model displays a strong first-order phase transition from a high-temperature, heavily defected phase to a low-temperature phase with enhanced short-range icosahedral order. This transition is compared to our observations of icosahedral phase formation to fix the values of the theoretical parameters.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Applied Physics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Johnson, William Lewis
Thesis Committee:
  • Unknown, Unknown
Defense Date:23 October 1987
Record Number:CaltechTHESIS:09272010-145542274
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:09272010-145542274
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6062
Collection:CaltechTHESIS
Deposited By: Benjamin Perez
Deposited On:27 Sep 2010 22:17
Last Modified:26 Dec 2012 04:30

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