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Title:Isotope effect for diffusion of tin in beta-titanium
Author(s):Jackson, Mark Sennett
Doctoral Committee Chair(s):Lazarus, David
Department / Program:Physics
Subject(s):isotope effect
diffusion of tin
tin isotopes
Abstract:The isotope effect for diffusion of in Ti has been measured at five temperatures in the bcc G-phase. Separation of the Sn isotopes was effected by 3-spectroscopy on electroplated sources. The effect is small and highly temperature-dependent, varying from 0.18 ± 0.03 at 9720 C to 0.37 ± 0.03 at 15250 C. When corrected for the mass difference between the Sn tracers used and the Ti solvent, the magnitude of the effect seems to be consistent with a relaxed vacancy mechanism as observed in normall bcc metals. Between 1100 and 12000 C the isotope effect parameter increases quite rapidly. The temperature variation seems to be inconsistent with the hypothesis that two competing mechanisms of bulk diffusion operate over the bee temperature range. The data do seem to be consistent with three possible mechanisms for diffusion: enhancement by dislocation networks which anneal out at higher temperatures, enhancement due to the presence of w-embryos at low temperatures, and diffusion by highly relaxed vacancies with a large coefficient of thermal expansion and specific heat of formation. The last explanation is preferred.
Issue Date:1976
Genre:Dissertation / Thesis
Rights Information:1976 Mark Sennett Jackson
Date Available in IDEALS:2011-07-05
Identifier in Online Catalog:1940732

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