Elsevier

Materials & Design

Volume 223, November 2022, 111134
Materials & Design

The role of Cr concentration and temperature on cavity swelling with co-injected helium in dual-ion irradiated Fe and Fe-Cr alloys

https://doi.org/10.1016/j.matdes.2022.111134Get rights and content
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Highlights

  • The non-monotonic nature of the cavity swelling behavior is related to the ratio of biased to unbiased sink strengths.

  • Cr dependence of swelling may be affected by solute trapping of defects leading to increased point defect recombination.

  • Higher He implantation rate causes a shift in the swelling peak to higher temperatures in both Fe and Fe-Cr alloys.

  • A bimodal cavity size distribution was observed in the 10 appm He/dpa samples, but not for 0.1 appm He/dpa.

  • Cr-enriched precipitates were observed in the Fe-14Cr sample irradiated at 400 °C.

Abstract

The level of chromium plays an essential role in irradiation tolerance of Fe-Cr ferritic alloys. However, conflicting results have been reported regarding the dependence of cavity swelling under irradiation on Cr level and temperature. Here, we have performed a comprehensive set of simultaneous dual-ion (Ni + He) irradiations to high dose (∼30 displacements per atom, dpa) at 400–550 °C on a series of ultra-high purity Fe and Fe-Cr binary alloys (3–14 wt.%Cr). Helium co-implantation rates of 0.1 and 10 appm He/dpa were selected to examine He synergistic effects relevant for fission and fusion reactor conditions, respectively. Cavities were observed in all irradiated samples by transmission electron microscopy. The results show that higher He implantation rate causes a shift in the swelling peak to higher temperatures in both Fe and Fe-Cr alloys. When assuming smaller cavities as biased sinks, the non-monotonic nature of the cavity swelling behavior is related to the ratio of biased to unbiased point defect sink strengths. Cr-enriched precipitates were observed in Fe-14Cr irradiated at 400 °C by atom probe tomography. Our analysis suggests the formation of Cr-enriched precipitates could suppress cavity swelling for Fe-Cr alloys with Cr content above 10 wt%.

Keywords

Fe-Cr ferritic alloys
Cavity/void swelling
Helium synergistic effect
Atom probe tomography
Transmission electron microscopy

Data availability

Data will be made available on request.

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Note to Elsevier: This manuscript has been co-authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so. The Department of Energy will provide public access to these results with full access to the published paper of federally sponsored research in accordance with the DOE Public Access Plan (https://energy.gov/downloads/doe-public-access-plan).