Transformation kinetics of delta prime precipitation in aluminum-lithium alloys
Yu, Ming Sheng
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/19733
Description
Title
Transformation kinetics of delta prime precipitation in aluminum-lithium alloys
Author(s)
Yu, Ming Sheng
Issue Date
1992
Doctoral Committee Chair(s)
Chen, Haydn
Department of Study
Materials Science and Engineering
Discipline
Materials Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Metallurgy
Language
eng
Abstract
The transformation kinetics of the early-stage of phase separation in an supersaturated Al-12 at.% Li alloy has been studied by means of time-resolved synchrotron radiation techniques. The simultaneous measurement of both the temporal evolution of the intensity profile from wide-angle x-ray diffraction (XRD) and small-angle x-ray scattering (SAXS) is a unique arrangement. The comparison of the integrated intensity from both the SAXS intensity profile and the XRD superlattice reflection provides the sequence of phase separation, such as ordering and decomposition. The combination of the rate of change of the integrated intensity from the superlattice reflection and the variation of ordered domain size suggest the likely division temperature, the congruent ordering temperature, T$\sb{\rm o}$, and the ordering instability temperature, T$\sb{-}$. In addition, the phase separation models, such as Cahn-Hilliard-Cook (CHC), Langer-Bar on-Miller (LBM) and Furukawa have been tested using the results of synchrotron radiation measurements. The dynamical scaling of the SAXS intensity profiles and the power growth law of peak positions and intensities have also been investigated.
In the late-stage of phase separation, the study focuses on the coarsening kinetics behavior of Al alloys with 9.7 at.% and 7.9 at.% lithium. The kinetics parameters, i.e. coarsening rate constants are determined from the in situ conventional SAXS measurements. The diffusivity, D, and the activation energy, $\gamma$, for the diffusion of lithium atoms within the solid solution can be calculated from these kinetics parameters. The correction for the volume fraction effect and the choice of the appropriate phase diagram can provide consistent and reasonable kinetics parameters.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
