Hydrogen segregation, defects, and interactions with dislocations in nickel and aluminum
Sirois, Ernest Joseph, Jr.
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https://hdl.handle.net/2142/20816
Description
Title
Hydrogen segregation, defects, and interactions with dislocations in nickel and aluminum
Author(s)
Sirois, Ernest Joseph, Jr.
Issue Date
1990
Doctoral Committee Chair(s)
Birnbaum, Howard K.
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
Engineering, Materials Science
Language
eng
Abstract
Deformation experiments were performed to determine the effects of hydrogen and carbon on the activation parameters for dislocation slip in macroscopic nickel tensile specimens. The results show that hydrogen increases the dislocation mobility in Ni and in Ni-H alloys by reducing the activation enthalpy for dislocation motion and carbon reduces the mobility by increasing the enthalpy. Stress relaxation results show that the relaxation proceeds in three stages, which may be characterized by different activation areas.
Secondary Ion Mass Spectroscopy experiments were performed to directly study the hydrogen (deuterium) distribution in several metal-hydrogen systems. Enhanced hydrogen (deuterium) concentration was observed at most grain boundaries, but not at coherent twin boundaries in Ni-H alloys which were exposed to low energy hydrogen (deuterium) plasma bombardment. Hydrogen (deuterium) was readily observed to segregate to a minority of grain boundaries in deformed, gaseous hydrogen charged, and low temperature aged Ni-H alloys.
Small angle X-ray scattering experiments were performed to study hydrogen related defects in Ni-H and in Al-H alloys. Results for Al-H alloys show defects which exhibit anisotropic scattering, typical of platelet defects. Ni-H alloys show defects which exhibit isotropic scattering, suggestive of spherical void defects.
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