Papers by Keyword: Zirconium

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Authors: Morten M. Eldrup, G.M. Hood, N.J. Pedersen, R.J. Schultz
Authors: Young Ho Lee, Hyung Kyu Kim
Abstract: An effort has been made in the present investigation to evaluate the wear resistance of nuclear fuel rods with a variation of the supporting spring shapes and their stiffness by conducting fretting wear tests in room temperature air and water. With increasing slip amplitude, the wear volume and maximum wear depth are increased with increasing slip amplitude. However, these are not linearly increased with increasing spring stiffness. After the wear test, the worn surfaces were observed to investigate the debris behavior and wear mechanism by using an optical microscope (OM). The results indicated that almost all of the wear debris remained between the contacting surfaces and the wear debris layers were well developed in room temperature air. Besides, some of the debris also remained on the worn surface in room temperature water. This result shows that the remaining debris effect on the worn surface was more dominant than the spring stiffness one. So, in order to improve the fretting wear resistance of a nuclear fuel rod, it is necessary to consider the debris behavior between contacting surfaces even though the supporting spring shape was optimized by considering the contact mechanics, material compatibility, etc. From the experimental results, the fretting wear mechanisms and the effect of spring properties were discussed.
Authors: K. Eloot, Annick De Paepe, J. Dilewijns, C. Standaert
Authors: O.A. Alexeev, A.A. Shmakov, E.A. Smirnov
Authors: O.A. Alexeev, A.A. Shmakov, E.A. Smirnov
Authors: Guillaume Vérité, F. Willaime, Chu Chun Fu
Abstract: The vacancy properties in group-IV hexagonal close-packed metals (Ti, Zr and Hf) have been investigated by Density Functional Theory (DFT) calculations performed with the SIESTA code. The migration energies are found to be systematically lower by »0.15 eV within the basal plane than out of the basal plane. The electronic origin of this significant contribution to diffusion anisotropy is evidenced by the analysis of the local electronic densities of states and by a comparison with and empirical potential. The average value of the migra- tion energy is in very good agreement with available experimental data in Zr. The activation energies for self-diffusion obtained assuming a vacancy mechanism are in good agreement with experiments in Zr and Hf, although slightly too small, but a significant discrepancy is observed in Ti.
Authors: Fanny Dyment, Manuel J. Iribarren, K. Vieregge, Christian Herzig
Authors: B.L. Henrie, Thomas A. Mason, J.F. Bingert
Abstract: Historically, twinning classification has been obtained by optical microscopy, bulk x-ray and neutron diffraction, and transmission electron microscopy (TEM). Recent research has shown that automated electron backscatter diffraction (EBSD) can be used to quantify twin content and thereby greatly improve the reliability of twinning statistics. An automated twin identification technique for use with EBSD has facilitated a greater understanding of deformation twinning in materials. The key features of this automated framework are the use of the crystallographic definition of twin relationships, and the correct identification of the parent orientation in a parent/twin pair. The complex nature of the parent/twin interactions required the use of a voting scheme to correctly identify parent orientations. In those few cases where the voting scheme was unable to determine parent orientation (< 2%) the algorithm allows for manual selection. Twin area fractions are categorized by operative twin systems along with secondary and tertiary twinning. These statistics are reported for deformation and annealing twin populations in deformed a-zirconium and asannealed 316L stainless steel, respectively. These improved twin statistics can help provide insight into the effect of deformation processes on microstructural evolution, as well as provide validation of plasticity models for materials that exhibit deformation twinning.
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