Equilibrium concentration of interstitials in aluminum just below the melting temperature
Gordon, Craig Alan
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https://hdl.handle.net/2142/31251
Description
Title
Equilibrium concentration of interstitials in aluminum just below the melting temperature
Author(s)
Gordon, Craig Alan
Issue Date
2000
Doctoral Committee Chair(s)
Granato, A.V.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Interstitialcy Theory
aluminum
non-contact electromagnetic acoustic transducer
Language
en
Abstract
The Interstitialcy Theory offers a unified description of the solid, liquid, and
amorphous states of condensed matter, including a direct criterion for the onset of
melting. A major prediction of the theory is that the equilibrium concentration of
interstitial defects should be only about an order of magnitude less than the vacancy
concentration near the melting temperature. Of the various properties affected by the
presence of interstitials, the shear modulus is known to be particularly sensitive.
A non-contact EMAT technique of ultrasonic generation and detection was used
to make high temperature measurements of the C44 and C' shear elastic moduli in
aluminum. The results show a large C44 deviation just below the melting temperature and
a much smaller effect for C', which is to be expected for interstitials in FCC crystals. The
results are analyzed to give a detected interstitial concentration of 1.7 ± 0.6 x 10^4 just
below the melting temperature of 933 K. This corresponds to a reasonable range for the
interstitial formation enthalpy and entropy, and supports the prediction of the
Interstitialcy Theory.
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