NSUF 19-1665: Defect Clustering in 316H Stainless Steel and High Entropy Alloy Under In-situ Irradiation at 600-700°C
Despite the promising results about the irradiation resistance of high entropy alloys, recent data on the morphology of irradiation-induced dislocation loops in the irradiated HEAs is insufficient and inconsistent. For instance, Some studies showed that the irradiation-induced dislocation loops decrease with increasing compositional complexity, while others showed an opposite trend. The contradicting results indicate that the irradiation process in HEAs is still not well understood, and further investigation is needed. In addition, most previous studies irradiated HEAs at 500°C and below, while the results for molten salt reactor-relevant temperatures (600-700°C) are still limited.Our previous works at 500°C showed that the size of dislocation loops increases with increasing compositional complexity. In addition, preliminary dynamic observations on Al0.3CoCrFeNi and pure nickel indicated that the mobility of defect clusters and point defects played a role in the resulting loop morphology. Therefore, experiments specifically designed to investigate the high-temperature (> 500°C) dynamic processes of dislocation loops as a function composition is important to understand currently-confusing data in literatures. This proposal aims to understand the irradiation behavior of HEAs at 600-700°C, as compared with 316H. The dynamic processes of dislocation loops are considered as the controlling factors to the distinctive microstructures observed at higher dose. 316H SS, Al0.3CoCrFeNi, CoCrFeMnNi and nickel will be consistently irradiated with 1 MeV Kr at 600°C, 650°C and 700°C in IVEM facility while the dynamic processes of dislocation loops will be recorded with high-frame-rate (up to 200 fps) camera. The temperatures were selected for molten salt reactors conditions. We will focus on the dynamic processes below:(1) Loop formation: by cascade condensation or by diffusion(2) 1/3 faulted loops unfaulting to ½ perfect loops(3) Oscillations and gliding frequency and distance of ½ perfect loops(4) Coalescence between loops with similar and dissimilar burgers vectors(5) The time for loops under critical size to disappear after cascade formation(6) Interaction between dislocation loops and preexisting dislocationsThe videos will be quantitatively analyzed to get properties (e.g. critical size for dislocation loops to be stable, critical size for faulted loop to unfault, rate of loop coalescence, etc.) dependence on irradiation temperature and composition. The dynamic information obtained from this proposal will be integrated into previously observed microstructural evolution of HEAs, 316H and nickel under the same irradiation condition to provide new perspectives for a more comprehensive explanation. With the successful understanding gained from this proposal, we will be able to correctly interpret the irradiation data and to evaluate high entropy alloys as compared with 316H SS. 5 days of IVEM access are quested to complete the 12 experimental conditions.
Additional Info
| Field | Value |
|---|---|
| Abstract | Despite the promising results about the irradiation resistance of high entropy alloys, recent data on the morphology of irradiation-induced dislocation loops in the irradiated HEAs is insufficient and inconsistent. For instance, Some studies showed that the irradiation-induced dislocation loops decrease with increasing compositional complexity, while others showed an opposite trend. The contradicting results indicate that the irradiation process in HEAs is still not well understood, and further investigation is needed. In addition, most previous studies irradiated HEAs at 500°C and below, while the results for molten salt reactor-relevant temperatures (600-700°C) are still limited.Our previous works at 500°C showed that the size of dislocation loops increases with increasing compositional complexity. In addition, preliminary dynamic observations on Al0.3CoCrFeNi and pure nickel indicated that the mobility of defect clusters and point defects played a role in the resulting loop morphology. Therefore, experiments specifically designed to investigate the high-temperature (> 500°C) dynamic processes of dislocation loops as a function composition is important to understand currently-confusing data in literatures. This proposal aims to understand the irradiation behavior of HEAs at 600-700°C, as compared with 316H. The dynamic processes of dislocation loops are considered as the controlling factors to the distinctive microstructures observed at higher dose. 316H SS, Al0.3CoCrFeNi, CoCrFeMnNi and nickel will be consistently irradiated with 1 MeV Kr at 600°C, 650°C and 700°C in IVEM facility while the dynamic processes of dislocation loops will be recorded with high-frame-rate (up to 200 fps) camera. The temperatures were selected for molten salt reactors conditions. We will focus on the dynamic processes below:(1) Loop formation: by cascade condensation or by diffusion(2) 1/3<111> faulted loops unfaulting to ½<110> perfect loops(3) Oscillations and gliding frequency and distance of ½<110> perfect loops(4) Coalescence between loops with similar and dissimilar burgers vectors(5) The time for loops under critical size to disappear after cascade formation(6) Interaction between dislocation loops and preexisting dislocationsThe videos will be quantitatively analyzed to get properties (e.g. critical size for dislocation loops to be stable, critical size for faulted loop to unfault, rate of loop coalescence, etc.) dependence on irradiation temperature and composition. The dynamic information obtained from this proposal will be integrated into previously observed microstructural evolution of HEAs, 316H and nickel under the same irradiation condition to provide new perspectives for a more comprehensive explanation. With the successful understanding gained from this proposal, we will be able to correctly interpret the irradiation data and to evaluate high entropy alloys as compared with 316H SS. 5 days of IVEM access are quested to complete the 12 experimental conditions. |
| Award Announced Date | 2019-02-08T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Wei-Ying Chen |
| Irradiation Facility | None |
| PI | Weiying Chen |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1665 |