University of Illinois Urbana-Champaign

Effect of atomic size on diffusion in metallic glasses

Wu, Hue-Min

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https://hdl.handle.net/2142/23204

Description

Title
Effect of atomic size on diffusion in metallic glasses
Author(s)
Wu, Hue-Min
Issue Date
1991
Doctoral Committee Chair(s)
Averback, Robert S.
Department of Study
  • Physics, Condensed Matter
  • Engineering, Metallurgy
  • Engineering, Materials Science
Discipline
  • Physics, Condensed Matter
  • Engineering, Metallurgy
  • Engineering, Materials Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • Physics, Condensed Matter
  • Engineering, Metallurgy
  • Engineering, Materials Science
Language
eng
Abstract
  • This thesis research is to study diffusion in amorphous alloys. Systematic investigations of atomic transport in metallic glasses are reported. Direct measurements of diffusion coefficients were performed by using secondary ion mass spectroscopy, by which the diffusion coefficients less than 10$\sp{-20}$ cm$\sp2$/sec can be measured with reasonable accuracy and annealing times. Amorphous Ni-Zr was used as a model system for these studies.
  • It was shown that atomic size plays an important role in the mechanisms of diffusion in this metallic glass. Differences in the diffusion behavior between small and large tracer diffusion atoms in amorphous Ni-Zr suggested that the diffusion mechanisms of the two constituent elements of the alloy are different. The dependence on alloy composition of the tracer diffusion coefficient of smaller atoms was fundamentally different than that of large atoms. The trends of the pre-exponential factors D$\sb{0}$ and activation enthalpies, $\Delta$H, support the idea that small atoms in metallic glass diffuse by localized defects and that large atoms require the collective motions of many atoms. Moreover, the strong correlation of the diffusion coefficient of small atoms and the formation enthalpy required to create a hole of the given diffusion atoms provide the direct evidence that point defect type mechanism dominates small atom diffusion in amorphous Ni-Zr. However, diffusion of large atoms can not be correlated to the hole formation enthalpies. The relevance of diffusion behavior to crystallization kinetics of amorphous Ni-Zr and to the kinetic of solid state amorphization transformation is discussed.
Type of Resource
text
Permalink
http://hdl.handle.net/2142/23204
Copyright and License Information
Copyright 1991 Wu, Hue-Min

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