X-Ray and Neutron Scattering Studies of Niobium-Hydrogen Alloys Near the Alpha-Prime to Beta Phase Transition
Chasnov, Robert
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https://hdl.handle.net/2142/71806
Description
Title
X-Ray and Neutron Scattering Studies of Niobium-Hydrogen Alloys Near the Alpha-Prime to Beta Phase Transition
Author(s)
Chasnov, Robert
Issue Date
1983
Department of Study
Metallurgy and Mining Engineering
Discipline
Metallurgical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Abstract
An experimental study of NbD(,x)(H(,x)) alloys (0.70 < x < 0.85) in the vicinity of the (alpha)'-(beta) phase transition was conducted using x-ray and elastic neutron scattering techniques in the temperature range 300 < T < 473 K. Diffuse scattering close to the Bragg peaks of the BCC (alpha)' phase was measured. The temperature dependence of the scattering was determined in the (alpha)' phase and the changes in the diffuse scattering were determined upon cooling through the (alpha)'-(beta) phase transition.
Calculations of the diffuse scattering were carried out using the distortion field around the hydrogen solutes and taking correlations between the interstitial solutes into account. Our interpretation of the diffuse scattering data leads to a qualitative picture of the interactions between the hydrogen interstitial atoms and the niobium host lattice atoms.
We have also observed "superlattice" reflections between the Bragg peaks of the BCC (alpha)' phase, resulting from static displacements of the niobium lattice. These have been interpreted as being due to the partial ordering of deuterium atoms on octahedral interstitial sites. Because these reflections were not observed for Nb-H alloys in this composition range, an interpretation based on D-D interactions is presented.
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