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The Effect of Grain Boundaries and Second-Phase Particles on Hydride Precipitation in Zirconium Alloys

Published online by Cambridge University Press:  28 January 2018

Said El Chamaa*
Affiliation:
Department of Materials and Centre for Nuclear Engineering, Imperial College London, SW7 2AZ
Mitesh Patel
Affiliation:
Department of Physics, Imperial College London, SW7 2AZ, UK
Catrin M. Davies
Affiliation:
Department of Mechanical Engineering, Imperial College London, SW7 2AZ, UK
Mark R. Wenman
Affiliation:
Department of Materials and Centre for Nuclear Engineering, Imperial College London, SW7 2AZ
*
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Abstract

Understanding the precipitation of brittle hydride phases is crucial in establishing a failure criterion for various zirconium alloy nuclear fuel cladding. Accordingly, it is important to quantify the sensitivity of hydride precipitation to the component microstructure. This experimental investigation focuses on two microstructural characteristics and their role as hydride nucleation sites: The grain size and the alloy chemical composition. Samples of commercially pure zirconium (Zr-702) and Zircaloy-4, each with a wide range of grain sizes, were hydrided to 100 ppm and micrographs of the hydride distribution were optically analyzed for inter-granular and intra-granular precipitate sites. For most grain sizes, it was found that a significantly lower fraction of the precipitated hydrides nucleated at grain boundaries in Zircaloy-4 than in Zr-702, suggesting that a higher SPP content encourages the formation of intra-granular hydrides. Moreover, this effect became more prominent as the grain size increased; large-grain specimens contained a higher fraction of intra-granular hydrides than small-grain specimens of both Zr-702 and Zircaloy-4, highlighting the potency of grain boundaries as nucleation sites and how SPPs can influence the hydride distribution profile.

Type
Articles
Copyright
Copyright © Materials Research Society 2018 

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References

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