Grain boundary phosphorus segregation in thermally aged low alloy steels

Hayato Nakata, Katsuhiko Fujii, Koji Fukuya, Ryuta Kasada, Akihiko Kimura

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33 Citations (Scopus)


Intergranular embrittlement due to grain boundary segregation of phosphorus is recognized as one of the potential degradation factors in irradiated reactor low alloy steels at high neutron fluence. In this study, low alloy steels thermally aged at 400-500°C were investigated to evaluate the correlation between phosphorus segregation and intergranular embrittlement. Phosphorus segregation determined using Auger electron spectroscopy increased after thermal aging above 450°C and was in good agreement with the calculated value based on McLean's model. No influence of thermal aging on tensile properties or hardness was observed. The ductile brittle transition temperature determined using a one-third size Charpy impact test increased at a P/Fe peak ratio of 0.14. These results indicated that there is a threshold level of phosphorus segregation for non-hardening embrittlement. The ductile to brittle transition temperature (DBTT) increased with the proportion of intergranular fracture, so this result shows that there is a relationship between DBTT and the proportion of intergranular fracture. The fracture stress decreases due to non-hardening embrittlement on the thermally aged material with high proportion of intergranular fracture.

Original languageEnglish
Pages (from-to)785-793
Number of pages9
Journaljournal of nuclear science and technology
Issue number7
Publication statusPublished - 2006
Externally publishedYes


  • Grain boundary segregation
  • Phosphorus segregation
  • Radiation embrittlement
  • Reactor pressure vessel steel

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering


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