Characterization of polyhedral nano-oxides and helium bubbles in an annealed nanostructured ferritic alloy

Journal Article · 14 January 2020 · Acta Materialia

DOI: https://doi.org/10.1016/j.actamat.2019.10.045 · OSTI ID:1599831

Stan, Tiberiu ^[1]; Wu, Yuan ^[1]; Ciston, Jim ^[2]; Yamamoto, Takuya ^[1]; Odette, G. Robert ^[1]

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1. Univ. of California, Santa Barbara, CA (United States)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Center for Electron Microscopy

Nanostructured ferritic alloys (NFAs) contain an ultra-high density of 2–4 nm fcc pyrochlore Y₂Ti₂O₇ nano-oxides (NOs) embedded in a bcc Fe-14Cr ferritic matrix. Characterization of helium interactions with NOs and associated Fe-Y₂Ti₂O₇ interfaces is important to the development of structural materials for nuclear fusion and fission applications. A benchmark 14YWT NFA was first annealed to coarsen the NOs, then insoluble helium was implanted at 700 °C to produce a high number density of bubbles. High-resolution scanning transmission electron microscopy characterization shows two dominant Fe-Y₂Ti₂O₇ crystallographic orientation relationships (cube-on-edge and cube-on-cube). The smallest NOs (≈ 2 nm) are associated with the smaller bubbles (≈ 1.5 nm), while some of the largest NOs (> 6 nm) have larger, and sometimes multiple, bubbles. NO corner {111} facets are the preferred sites for He bubble nucleation. A refined sequence of events for He trapping and bubble formation is presented. Finally, these observations offer new insight on He management in NFAs, and provide a foundation for detailed modeling studies.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
• Grant/Contract Number: AC02-05CH11231; FG03-94ER54275
• OSTI ID: 1599831
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: C Vol. 183; ISSN 1359-6454
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English