Abstract
Determining the microstructure evolution of oxide dispersion-strengthened (ODS) alloys is important for predicting the safety and structural integrity of fast reactors. In particular, understanding the co-evolution of dispersoids with the dislocation loops and network is critical for a comprehensive understanding of the microstructure response to radiation. Ion irradiations were performed on oxide dispersion strengthened MA956 with 5 MeV Fe++ ions from 400 to 500 °C at doses ranging from 50 to 200 dpa. Characterization was performed primarily with scanning transmission electron microscopy and energy-dispersive x-ray spectroscopy to investigate the Y-Al-O dispersoids, voids and dislocations. Regardless of temperature, the dispersoids increased in diameter and decreased in number density, which was attributed to an Ostwald coarsening mechanism supported by calculations of the radiation enhanced diffusion and ballistic dissolution. MA956 demonstrated excellent void swelling resistance and did not form voids except at 450 °C, 200 dpa where voids nucleated upon dispersoids. The dislocation loop diameter was highest at 500 °C followed by 400 °C then 450 °C while number density tended to decrease with dose. The dislocation behavior was explained as a function of the evolving defect kinetics, utilizing rate theory to calculate point defect concentrations and the increasing diffusivity of vacancies. At 400 °C, the interstitials had high enough diffusivity to nucleate new loops but vacancies remained relatively immobile. At 450 °C, vacancies are able to annihilate interstitials due to non-negligible mutual recombination causing the decreased number density of loops. At 500 °C, vacancy and interstitials are both mobile where the interstitials coalesce to form larger loops and vacancies provide a pathway for solutes diffusing to and from dispersoids.
| Original language | English |
|---|---|
| Article number | 101024 |
| Journal | Nuclear Materials and Energy |
| Volume | 28 |
| DOIs | |
| State | Published - Sep 2021 |
| Externally published | Yes |
Funding
Research supported by the Defense Threat Reduction Agency (DTRA) through grant HDTRA113691. This work was also supported by the U.S. Department of Energy, Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07- 051D14517 as part of the Nuclear Science User Facilities’ Rapid Turnaround Experiment program (17-906, 17-1032 and 18-1396). This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy, Department of Defense or the United States Government. The authors gratefully acknowledge O. Toader and the MIBL staff and graduate students for assistance in ion irradiation. We also thank Y. Wu for assistance at CAES and L. He, B. Kombaiah and X. Liu for assistance with characterization studies performed at the MFC. The authors acknowledge the Open Campus program at Army Research Laboratory in Aberdeen, MD for providing access to characterization suite. The authors thank D. Woodley for many fruitful discussions. Research supported by the Defense Threat Reduction Agency (DTRA) through grant HDTRA113691. This work was also supported by the U.S. Department of Energy, Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07- 051D14517 as part of the Nuclear Science User Facilities? Rapid Turnaround Experiment program (17-906, 17-1032 and 18-1396). This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy, Department of Defense or the United States Government. The authors gratefully acknowledge O. Toader and the MIBL staff and graduate students for assistance in ion irradiation. We also thank Y. Wu for assistance at CAES and L. He, B. Kombaiah and X. Liu for assistance with characterization studies performed at the MFC. The authors acknowledge the Open Campus program at Army Research Laboratory in Aberdeen, MD for providing access to characterization suite. The authors thank D. Woodley for many fruitful discussions.
| Funders | Funder number |
|---|---|
| Army Research Laboratory in Aberdeen | |
| CAES | |
| U.S. Department of Defense | |
| U.S. Department of Energy | 17-906, 18-1396, 17-1032, DE-AC07- 051D14517 |
| Defense Threat Reduction Agency | HDTRA113691 |
| Office of Nuclear Energy |
Keywords
- Ion irradiation
- MA956
- Microstructure evolution
- Oxide dispersion strengthened alloy