SYMPOSIA PAPER Published: 28 July 2021
STP162220190019

Characterization of Hydrides and the α-Zr Matrix in Zirconium Alloys: Effects of Stresses, Microstructure, and Neutron Irradiation on Hydride Texture, Terminal Solid Solubility, and Dislocation Structure

Source

Synchrotron X-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy experiments were performed on samples from Zr-2.5Nb alloy pressure tubes and Zircaloy-4 fuel channels materials in order to define hydride precipitation temperatures, hydride texture, the matrix hydride orientation relationship, and dislocation densities. For Zr-2.5Nb, studies included in situ constant stress tests performed on dog-bone specimens cycled between room temperature and 400°C, where hydrides were completely dissolved and reprecipiated. For Zircaloy-4, analysis included ex-service Zircaloy-4 irradiated to ~ 1022 neutrons/cm2. Careful interpretation and analysis of azimuthal variations around the Debye-Scherrer rings allowed a clear description of both texture and dislocation densities of δ-hydride precipitates. The main findings are: (1) In Zr-2.5Nb pressure tubes, the terminal solid solubility for hydride dissolution and the terminal solid solubility for precipitation (TSSP) temperatures depend on the orientation of the parent α-Zr grain. Hydrides both precipitate and dissolve at slightly lower temperatures (~ 5°C and ~ 15°C, respectively) in grains having their c-axis parallel to the tube hoop direction than those with their c-axis ~ 20° off from the hoop direction. (2) Application of a stress along the tube hoop direction during precipitation increases TSSP temperatures and favors hydride precipitation on grains with c-axes stretched by the load. For grains with the c-axis parallel to the applied load, TSSP temperatures increase at a rate of (0.08 ± 0.02)°C/MPa, nearly two orders of magnitude higher than previous estimates. (3) Precipitates of δ-hydride are heavily dislocated, yet display large variations (1.6 to 10 × 1014 m−2) depending on the microstructure and hydrogen content of the parent material.

Author Information

Vizcaino, Pablo
Centro Atómico Ezeiza, Presbítero Juan González y Aragón N 15, Ezeiza, Buenos Aires, AR
Flores, Alejandra, V.
Centro Atómico Ezeiza, Presbítero Juan González y Aragón N 15, Ezeiza, Buenos Aires, AR
Vicente Alvarez, Miguel, A.
Centro Atómico Bariloche, & Laboratorio Argentino de Haces de Neutrones (LAHN), Bariloche, Río Negro, AR
Santisteban, Javier, R.
Centro Atómico Bariloche, & Laboratorio Argentino de Haces de Neutrones (LAHN), Bariloche, Río Negro, AR
Domizzi, Gladys
Centro Atómico Constituyentes, Buenos Aires, AR
Tolley, Alfredo
Centro Atómico Bariloche, Bariloche, AR
Condó, Adriana
Centro Atómico Bariloche, Bariloche, AR
Almer, Jonathan, D.
Argonne National Laboratory Advanced Photon Source, Lemont, IL, US
Price: $25.00
Contact Sales
Related
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Details
Pages: 786–811
DOI: 10.1520/STP162220190019
ISBN-EB: 978-0-8031-7691-1
ISBN-13: 978-0-8031-7690-4