Speaker
Description
Understanding the behaviour of hydrogen in zirconium-based alloys is desired since these alloys are used for fuel cladding in light water nuclear reactors but are known to suffer from hydrogen pick-up and embrittlement during service, and delayed hydride cracking (DHC) during storage.
Reliably and accurately imaging hydrogen with atom probe tomography (APT) is challenging due to several phenomena that can lead to an artificial increase in hydrogen signal during an APT experiment[1,2]. With certain materials, such as zirconium, there is the added complication that common sample preparation routes can introduce additional hydrogen into specimens and even lead to phase transformations, altering the microstructure prior to analysis[3].
In this talk, we build on the work of Hanlon et al.[3] and Mayweg et al.[4] to show how the hydrogen levels present in zirconium samples vary in specimens prepared using Ga+ and Xe+ focused ion beams (FIB) at ambient and cryogenic temperatures. Transmission electron micrographs will be shown alongside APT data and estimates will be made as to the amount of hydrogen present in APT needles after FIB preparation.
We will then present results from a recent article[5], discussing how the use of cryogenic FIB preparation of zirconium samples can be combined with careful data analysis and computational modelling to enhance our understanding of hydrogen behaviour within the microstructure of zirconium alloys.
References
1. Yoo, S. H. et al. Origins of the hydrogen signal in atom probe tomography: Case studies of alkali and noble metals. New Journal of Physics 24, (2022).
2. Sundell, G., Thuvander, M. & Andrén, H. O. Hydrogen analysis in APT: Methods to control adsorption and dissociation of H2. Ultramicroscopy 132, 285–289 (2013).
3. Hanlon, S. M., Persaud, S. Y., Long, F., Korinek, A. & Daymond, M. R. A solution to FIB induced artefact hydrides in Zr alloys. Journal of Nuclear Materials 515, 122–134 (2019).
4. Mayweg, D., Eriksson, J., Bäcke, O., Breen, A. J. & Thuvander, M. Focused Ion Beam induced hydride formation does not affect Fe, Ni, Cr-clusters in irradiated Zircaloy-2. Journal of Nuclear Materials 581, 154444 (2023).
5. Jenkins, B. M. et al. Experimental and modelling evidence for hydrogen trapping at a β-Nb second phase particle and Nb-rich nanoclusters in neutron-irradiated low Sn ZIRLO. Journal of Nuclear Materials 587, 154755 (2023).
