Abstract
Hydride precipitation and reorientation has the potential to embrittle zirconium alloys. This study aims to better understand the influence of the Zr microstructure on hydride precipitation and reorientation. Specifically, the crystallography, phase stability and morphology of hydride precipitation was correlated to microstructural variations due to changes in the metallurgical state of the zirconium alloy. The work highlights, that microstructural features induced during recrystallisation have a significant influence on the distribution and orientation of hydrides when no external stress is applied. The stability of ϒ-hydride was shown to be dictated by metallurgical state whereby its formation was promoted in the recrystallised sample owing to its reduced strength. The influence of grain orientation on ϒ stability was also explored. It was highlighted that upon cooling, grains oriented in the <101 ̅0> direction are under compression such that ϒ-hydride formation is supressed. This study suggests that the extent of reorientation is driven by differences in hydrogen content of the alloy as well as the applied stress during reorientation, whilst the influence of the metallurgical state still remains unclear. Quantification of the dislocation density in both the matrix and hydride during precipitation highlighted that extensive matrix recovery takes place during hydriding. It was also shown that the dislocation density in the hydride is lower after thermomechanical loading whereby the presence of dislocation nests left behind after initial hydride precipitation and dissolution could provide more space for the hydride to precipitate into.
| Original language | English |
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| Title of host publication | ASTM 20th International Symposium on Zirconium in the Nuclear Industry |
| Publication status | Accepted/In press - 4 Nov 2022 |