Molecular Dynamics Study of Microstructural Evolution in Alloys Subjected to Severe Plastic Deformation
Odunuga, Samson Olusikunanu
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https://hdl.handle.net/2142/82810
Description
Title
Molecular Dynamics Study of Microstructural Evolution in Alloys Subjected to Severe Plastic Deformation
Author(s)
Odunuga, Samson Olusikunanu
Issue Date
2007
Doctoral Committee Chair(s)
Averback, Robert S.
Department of Study
Materials Science and Engineering
Discipline
Materials Science and 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 atomic transport resulting from plastic deformation has been analyzed in new depths by tracking the evolution of pair of marker atoms. This analysis has proved to be a powerful tool in identifying the deformation mechanisms, including the glide of leading and trailing partial dislocations, and vacancy assisted atomic jumps during deformation, as well as quantifying the relative contributions of these mechanisms. It is found that the glide of dislocations plays a more important role than previously thought in accommodating plastic deformation in nanocrystalline alloys. A new property of the atomic mixing by plastic deformation that has been uncovered is that the effective diffusion coefficient increases, nearly linearly, with the separation distance of pairs of atoms. This superdiffusive mixing is revealed by monitoring the relative displacement of atoms as a function of the separation distance. This result can be tested experimentally by measuring the rate of dissolution of precipitates during deformation. This finding also provides a direct rationalization for the stabilization of compositional patterns when thermal diffusion and forced mixing compete.
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