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As one candidate alloy for future Generation IV and fusion reactors, a dual-phase 12Cr oxide-dispersion-strengthened (ODS) alloy was developed for high temperature strength and creep resistance and has shown good void swelling resistance under high damage self-ion irradiation at high temperature. However, the effect of helium and its combination with radiation damage on oxide dispersoid stability needs to be investigated. In this study, 120 keV energy helium was preloaded into specimens at doses of 1 × 1015 and 1 × 1016 ions/cm2 at room temperature, and 3.5 MeV Fe self-ions were sequentially implanted to reach 100 peak displacement-per-atom at 475 °C. He implantation alone in the control sample did not affect the dispersoid morphology. After Fe ion irradiation, a dramatic increase in density of coherent oxide dispersoids was observed at low He dose, but no such increase was observed at high He dose. The study suggests that helium bubbles act as sinks for nucleation of coherent oxide dispersoids, but dispersoid growth may become difficult if too many sinks are introduced, suggesting that a critical mass of trapping is required for stable dispersoid growth.
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The Effect of Internal Free Surfaces on Void Swelling of Irradiated Pure Iron Containing Subsurface Trenches
We studied the effects of internal free surfaces on the evolution of ion-induced void swelling in pure iron. The study was initially driven by the motivation to introduce a planar free-surface defect sink at depths that would remove the injected interstitial effect from ion irradiation, possibly enhancing swelling. Using the focused ion beam technique, deep trenches were created on a cross section of pure iron at various depths, so as to create bridges of thickness ranging from 0.88 μm to 1.70 μm. Samples were then irradiated with 3.5 MeV Fe2+ ions at 475 °C to a fluence corresponding to a peak displacement per atom dose of 150 dpa. The projected range of 3.5 MeV Fe2+ ions is about 1.2 μm so the chosen bridge thicknesses involved fractions of the ion range, thicknesses comparable to the mean ion range (peak of injected interstitial distribution), and thicknesses beyond the full range. It was found that introduction of such surfaces did not enhance swelling but actually decreased it, primarily because there were now two denuded zones with a combined stronger influence than that of the injected interstitial. The study suggests that such strong surface effects must be considered for ion irradiation studies of thin films or bridge-like structures.
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- Award ID(s):
- 1708788
- PAR ID:
- 10096368
- Date Published:
- Journal Name:
- Crystals
- Volume:
- 9
- Issue:
- 5
- ISSN:
- 2073-4352
- Page Range / eLocation ID:
- 252
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/cryst9050252
