Phase transformations during cooling from the βZr phase temperature domain in several hydrogen-enriched zirconium alloys studied by in situ and ex situ neutron diffraction - Archive ouverte HAL Access content directly
Journal Articles Acta Materialia Year : 2020

Phase transformations during cooling from the βZr phase temperature domain in several hydrogen-enriched zirconium alloys studied by in situ and ex situ neutron diffraction

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Thai Le Hong
  • Function : Author
Isabelle Turque
  • Function : Author
Jean-Christophe Brachet
Jérôme Crépin
Gilles André
  • Function : Author
Quentin Barres
  • Function : Author
Raphaëlle Guillou
  • Function : Author
Caroline Toffolon-Masclet
Jean-Marc Joubert
Matthieu Le Saux

Abstract

In hypothetical accidental conditions, zirconium-based nuclear fuel claddings can absorb high hydrogen contents (up to several thousand wppm) and be exposed to high temperatures (βZr phase temperature range) before being cooled. This paper thoroughly investigates the microstructural and microchemical evolutions that take place in such conditions. Two zirconium-based alloys and unalloyed zirconium were pre-charged with hydrogen at various contents up to 3300 wppm and heat-treated at 1000 or 850 °C. Neutron diffraction analyses were performed in situ upon slow cooling from 700 °C and at room temperature. In the materials containing 3300 wppm of hydrogen, βZr progressively transforms into αZr during slow cooling then extensively transforms into αZr and δZrH2-x hydrides precipitate via a eutectoid reaction. Thermodynamic predictions at equilibrium are in good agreement with the experimental results. However, depending on the cooling scenario and the average hydrogen content, the precipitation of γZrH hydrides, potentially metastable, is evidenced below 350 °C and a significant amount of hydrogen can remain in solid solution in αZr. These metallurgical evolutions and the evolution of the different phase lattice parameters are strongly influenced by the partitioning of oxygen and hydrogen (revealed by electron probe and elastic recoil detection microanalyses) that occurs during the βZr to αZr transformation and hydride precipitation.
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Dates and versions

hal-02956376 , version 1 (09-11-2020)

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Thai Le Hong, Isabelle Turque, Jean-Christophe Brachet, Jérôme Crépin, Gilles André, et al.. Phase transformations during cooling from the βZr phase temperature domain in several hydrogen-enriched zirconium alloys studied by in situ and ex situ neutron diffraction. Acta Materialia, 2020, 199, pp.453-468. ⟨10.1016/j.actamat.2020.08.061⟩. ⟨hal-02956376⟩
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