Effect of Nb and Fe on damage evolution in a Zr-alloy during proton and neutron irradiation

E. Francis, R. Prasath Babu, A. Harte, T. L. Martin, P. Frankel, D. Jädernäs, J. Romero, L. Hallstadius, P. A.J. Bagot, M. P. Moody, M. Preuss

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Abstract

Detailed analysis was carried out on proton and a neutron irradiated Nb-containing Zr-alloy to study the evolution of dislocation loop size and densities as well as the formation and evolution of irradiation-induced precipitation/clustering. The results obtained here have been contrasted against previously published work on a Nb-free Zr-alloy [1, 2] to investigate the mechanistic reason for the improved resistance to irradiation-induced growth of Nb-containing Zr alloys. The combined use of bright field scanning transmission electron microscopy, ultra-high-resolution energy dispersive spectroscopy and atom probe tomography analysis provides evidence of evenly distributed radiation-induced Nb clusters that have formed during the early stage of proton irradiation and Fe-rich nano-rods near Fe-containing second phase particles. The former seems to have a profound effect on <a> loop and subsequent <c> loop formation, keeping <a> loop size small but number density high while <c> loops seem to initially form at similar dose levels compared to a Nb-free alloy but <c> loop line density does not increase during further irradiation. It is hypothesized that the formation of the Nb nano-precipitates/clusters significantly hinders mobility and growth of <a> loops, resulting in a small size, high number density and limited ability of <a> loops to arrange along basal traces compared to Nb-free Zr-alloys. It is suggested that it is the limited <a> loop arrangement that slows down <c> loop formation and the root cause for the high resistance of Nb-containing Zr-alloys to irradiation-induced growth.

Original languageEnglish
Pages (from-to)603-614
Number of pages12
JournalActa Materialia
Volume165
DOIs
Publication statusPublished - 15 Feb 2019
Externally publishedYes

Keywords

  • Atom probe tomography
  • Breakaway growth
  • Clusters
  • Dislocation loops
  • Low-Sn ZIRLO™
  • Radiation induced precipitation
  • TEM

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