Papers by Author: C.R. Hubbard

Abstract: Neutron incoherent scattering measurements were conducted on Zircaloy-4 round bars. The specimens were charged in a tube furnace at 430 °C, using a 12.5 vol. % hydrogen in an argon mixture for 30, 60, and 90 minutes at 13.8 kPa pressure. The volume-average neutron diffraction measurements showed the presence of the face-centered-cubic delta zirconium hydride (δ-ZrH2) phase in the hydrogenated specimens. The assessment of the background in the diffraction profiles due to the incoherent scattering from the hydrogen atoms was carried out by performing inelastic scans around zero energy transfer and at a fixed two-theta value for which there was only flat background and no coherent scattering. To estimate the relative amount of hydrogen in the Zircaloy-4 samples, the increase in incoherent scattering intensities with hydrogen content was calibrated using samples for which the hydrogen content was known. Measurement of the background scattering from locations within the round bar was also performed to map the distribution of hydrogen content.

Abstract: Localized heating was imposed on a 6061-T6 aluminum alloy plate to cause thermal strains, and simultaneously interplanar spacing changes were measured using in-situ time-resolved neutron diffraction techniques. Two different methods were used: 1) direct real-time measurements of the transient behavior and 2) a series of measurements based on the quasi-steady state (QSS) principle. A comparison of the two results shows that the QSS method can represent the transient behavior under the current experimental conditions.