A transmission electron microscopy study of EBR-II neutron-irradiated austenitic stainless steel 304 and nickel-base alloy X-750

Xiang Liu, Lingfeng He, Huan Yan, Mukesh Bachhav, James F. Stubbins

Research output: Contribution to journalArticle

Abstract

The microstructure of EBR-II neutron-irradiated austenitic stainless steel 304 and nickel-base alloy X-750 was investigated. Both alloys were irradiated at low dose rates (∼2 × 10−8 dpa/s) to a neutron fluence of 6.9 × 1022 n/cm2 (E > 0.1 MeV) at 371–389 °C. Different types of defects, including Frank loops, cavities, and precipitates were characterized. The Frank loops in Type 304 stainless steel (SS) are larger in size (∼50 nm in diameter) and lower in number density (2.58 × 1021 m−3), compared to most previous higher dose rate neutron irradiation studies. The Frank loops in X-750 have an average size 26.0 nm of and a number density of 9.44 × 1021 m−3. In 304 SS and X-750, cavities are of ∼20 nm and ∼14 nm in diameter, respectively. The swelling of both alloys was found to be insignificant. In 304 SS, Ni and Si were found enriched at the cavity surfaces and Ni,Si-rich precipitates were also found. Multivariate statistical analysis using non-negative matrix factorization reveals that these Ni,Si-rich precipitates contain only ∼5.7 at.% Si, differing from the Ni3Si γ’ precipitates found in several previous studies. In X-750, L12-structured γ’ precipitates were found, and multivariate statistical analysis confirmed the 3:1 stoichiometry (Ni3(Ti,Al)) of the γ’ precipitates and the superlattice reflections confirmed the stability of the crystal structure of these γ’ precipitates, indicating higher-than-expected precipitate stability under high-dose neutron irradiation.

Original languageEnglish (US)
Article number151851
JournalJournal of Nuclear Materials
Volume528
DOIs
StatePublished - Jan 2020

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austenitic stainless steels
Austenitic stainless steel
Nickel
Precipitates
precipitates
Neutrons
nickel
Transmission electron microscopy
neutrons
transmission electron microscopy
Stainless Steel
multivariate statistical analysis
stainless steels
Stainless steel
Neutron irradiation
neutron irradiation
dosage
cavities
Dosimetry
Statistical methods

Keywords

  • Frank loops
  • Neutron irradiation
  • Nickel-base alloys
  • Stainless steel
  • Superlattice reflection
  • Transmission electron microscopy (TEM)

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Materials Science(all)
  • Nuclear Energy and Engineering

Cite this

A transmission electron microscopy study of EBR-II neutron-irradiated austenitic stainless steel 304 and nickel-base alloy X-750. / Liu, Xiang; He, Lingfeng; Yan, Huan; Bachhav, Mukesh; Stubbins, James F.

In: Journal of Nuclear Materials, Vol. 528, 151851, 01.2020.

Research output: Contribution to journalArticle

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abstract = "The microstructure of EBR-II neutron-irradiated austenitic stainless steel 304 and nickel-base alloy X-750 was investigated. Both alloys were irradiated at low dose rates (∼2 × 10−8 dpa/s) to a neutron fluence of 6.9 × 1022 n/cm2 (E > 0.1 MeV) at 371–389 °C. Different types of defects, including Frank loops, cavities, and precipitates were characterized. The Frank loops in Type 304 stainless steel (SS) are larger in size (∼50 nm in diameter) and lower in number density (2.58 × 1021 m−3), compared to most previous higher dose rate neutron irradiation studies. The Frank loops in X-750 have an average size 26.0 nm of and a number density of 9.44 × 1021 m−3. In 304 SS and X-750, cavities are of ∼20 nm and ∼14 nm in diameter, respectively. The swelling of both alloys was found to be insignificant. In 304 SS, Ni and Si were found enriched at the cavity surfaces and Ni,Si-rich precipitates were also found. Multivariate statistical analysis using non-negative matrix factorization reveals that these Ni,Si-rich precipitates contain only ∼5.7 at.{\%} Si, differing from the Ni3Si γ’ precipitates found in several previous studies. In X-750, L12-structured γ’ precipitates were found, and multivariate statistical analysis confirmed the 3:1 stoichiometry (Ni3(Ti,Al)) of the γ’ precipitates and the superlattice reflections confirmed the stability of the crystal structure of these γ’ precipitates, indicating higher-than-expected precipitate stability under high-dose neutron irradiation.",
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AB - The microstructure of EBR-II neutron-irradiated austenitic stainless steel 304 and nickel-base alloy X-750 was investigated. Both alloys were irradiated at low dose rates (∼2 × 10−8 dpa/s) to a neutron fluence of 6.9 × 1022 n/cm2 (E > 0.1 MeV) at 371–389 °C. Different types of defects, including Frank loops, cavities, and precipitates were characterized. The Frank loops in Type 304 stainless steel (SS) are larger in size (∼50 nm in diameter) and lower in number density (2.58 × 1021 m−3), compared to most previous higher dose rate neutron irradiation studies. The Frank loops in X-750 have an average size 26.0 nm of and a number density of 9.44 × 1021 m−3. In 304 SS and X-750, cavities are of ∼20 nm and ∼14 nm in diameter, respectively. The swelling of both alloys was found to be insignificant. In 304 SS, Ni and Si were found enriched at the cavity surfaces and Ni,Si-rich precipitates were also found. Multivariate statistical analysis using non-negative matrix factorization reveals that these Ni,Si-rich precipitates contain only ∼5.7 at.% Si, differing from the Ni3Si γ’ precipitates found in several previous studies. In X-750, L12-structured γ’ precipitates were found, and multivariate statistical analysis confirmed the 3:1 stoichiometry (Ni3(Ti,Al)) of the γ’ precipitates and the superlattice reflections confirmed the stability of the crystal structure of these γ’ precipitates, indicating higher-than-expected precipitate stability under high-dose neutron irradiation.

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KW - Superlattice reflection

KW - Transmission electron microscopy (TEM)

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