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http://hdl.handle.net/11375/7492
Title: | The transition from internal oxidation to external oxidation is silver-zinc alloys |
Authors: | Lesychyn, Nickolas Michael |
Advisor: | Smeltzer, W.W. Purdy, G.R. |
Department: | Metallurgy and Materials Science |
Keywords: | Materials Science and Engineering;Metallurgy;Materials Science and Engineering |
Publication Date: | Mar-1980 |
Abstract: | <p>The investigation concentrates on the morphology of the oxidation products produced in Ag-1.8, 7.5, 10.9, 12.9 and 18.7 wt % Zn alloys at 550°C under an oxygen pressure of 1 atm. Particular attention is given to the structure of the internal ZnO produced and the morphological development of the internal precipitation zone in the alloys containing Ag-1.8, 7.5 and 10.9 wt % Zn. Penetration depth of the internal ZnO was measured using a light microscope, and was observed to obey the parabolic law. A model based on volume diffusion control of oxygen has been proposed for the velocity of the internal ZnO precipitates.</p> <p>The Ag-12.9 wt % Zn alloy was observed to form an internal ZnO scale in combination with an external ZnO scale. An exclusive protective external scale of ZnO is formed on the Ag-18.7 wt % Zn alloy. The growth of the scale was found to obey parabolic kinetics. The morphological development of the external ZnO on the above alloys has also been studied.</p> <p>The theoretical basis for the transition from internal to external scale formation has been given according to the Wagner(²⁶) criteria for binary alloys.</p> <p>It was necessary to extend the Wagner binary treatment for the transition into a ternary thermodynamic and diffusion analysis. A portion of the Ag-Zn-O ternary isotherm has been proposed, thus making possible the placement of representative diffusion paths.</p> |
URI: | http://hdl.handle.net/11375/7492 |
Identifier: | opendissertations/2767 3809 1409127 |
Appears in Collections: | Open Access Dissertations and Theses |
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fulltext.pdf | 3.63 MB | Adobe PDF | View/Open |
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