Abstract
Ferritic-martensitic (FM) steels for in-vessel components in proposed fusion reactors are expected to suffer from high levels of displacement damage and helium (He) generation by neutron transmutation. However, a thorough understanding of the He synergistic effects on the cavity swelling in FM steels is still not well established. To gain fundamental insights into the He effect on cavity swelling, high purity Fe and Fe-10 wt.% Cr ferritic model alloys were irradiated with 8 MeV Ni ions and co-implanted He ions at 400 to 550 °C up to 30 displacements per atom (dpa) with He implantation rates of 0.1, 10 and 50 appm He/dpa. The current study focuses on the 50 appm He/dpa, 500 °C behavior vs. 0.1 and 10 appm He/dpa. Irradiation-induced defects, including cavities, dislocation loops, and dislocation networks were characterized using transmission electron microscopy (TEM). In the grain interior, a bimodal cavity size distribution was observed in the 10 and 50 appm He/dpa samples, but not for 0.1 appm He/dpa. Cavity swelling was maximized at intermediate He implantation rates of ∼10 appm He/dpa for both ion-irradiated Fe and Fe-10Cr alloys. The cavity swelling behavior as a function of He implantation rate appears to be controlled by the He/dpa-dependent variation of cavity sink strengths. Treating small bubbles as biased sinks for interstitial absorption can significantly increase the ratio of biased to unbiased sink strengths (Q) and results in maximized cavity swelling for a Q ratio close to one.
| Original language | English |
|---|---|
| Article number | 153907 |
| Journal | Journal of Nuclear Materials |
| Volume | 569 |
| DOIs | |
| State | Published - Oct 2022 |
Funding
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 ( http://energy.gov/downloads/doe-public-access-plan ). We acknowledge the staff and students of Michigan Ion Beam Laboratory (MIBL) for their assistance with ion irradiation and implantations. Electron Microscopy was performed with the JEM-ARM200F microscope at the Material and Chemical Research Laboratories, which was supported by the Industrial Technology Research Institute , Taiwan. We thank Drs. Roger Stoller, Brian Wirth, William Weber, and Haixuan Xu for their insightful comments and suggestions. Funding: This research was sponsored by the Office of Fusion Energy Sciences, U.S. Department of Energy under grant # DE-SC0006661 with the University of Tennessee (YRL and SJZ) and contract DE-AC05–00OR22725 with UT-Battelle, LLC (AB and SJZ). The fabrication of the Fe-Cr binary alloys has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training program 2019–2020 under Grant Agreement No. 633053. The authors would also like to acknowledge funding from the State of Tennessee and Tennessee Higher Education Commission (THEC) through their support of the Center for Materials Processing.
Keywords
- Cavity swelling
- Ferritic alloy
- Helium effects
- Radiation damage
- Transmission electron microscopy
