Isotope effect for diffusion of tin in beta-titanium
Jackson, Mark Sennett
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https://hdl.handle.net/2142/25657
Description
Title
Isotope effect for diffusion of tin in beta-titanium
Author(s)
Jackson, Mark Sennett
Issue Date
1976
Doctoral Committee Chair(s)
Lazarus, David
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
isotope effect
diffusion of tin
beta-titanium
bcc
tin isotopes
Language
en
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.
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