Phase and texture analysis of a hydride blister in a Zr-2.5%Nb tube by synchrotron X-ray diffraction

This paper presents a detailed phase and texture study within and around a hydride blister grown on the surface of a Zr-2.5%Nb pressure tube. The analysis is based on synchrotron X-ray diffraction experiments using an 80 keV photon beam and a high-speed area detector placed in transmission geometry. It was found that the blister is composed of two main phases, alpha-Zr and delta-ZrH, with a composition which changes locally across the blister. No location within the blister presents pure delta zirconium hydride, with a maximum of 80% for the volume fraction of delta hydride at the center of the blister. The texture observed for both phases in the original pressure tube remains essentially unaltered across the hydride blister. A detailed analysis of this texture using well-known parent precipitate relationships shows that some selective precipitation occurs at alpha-Zr grains with their c-axis under a tensile stress, and on grains with grain boundaries favorably aligned for hydride nucleation. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.