In-situ Observation of Irradiation Induced Defects in Fe and Fe-Cr Alloys
Bibliographic record
Abstract
The selection of structure materials is a key issue for achieving the success of future fusion and advanced fission reactors. Candidate materials for these applications include reduced-activation ferritic-martensitic (RAFM) steels with Cr contents ranging between 9-12%. These steels have better thermal properties and higher swelling resistance than austenitic steels, but may become embrittled under irradiation at temperatures less than about 400C It is important to develop a detailed mechanistic understanding of the development of radiation damage in ferritic alloys, which is lacking at present. The work reported here is part of this endeavor. The experiments of heavy-ion irradiation in iron was performed by using Argonne IVEM-Tandem Facility, which comprises an electron microscope linked to a heavy-ion accelerator. Thin foils of pure Fe were irradiated with 150 keV Fe+ ions at temperatures 30-500 o C. Dynamic observations under weak-beam diffraction conditions followed the evolution of damage over doses 0-10 dpa. At low doses, 1 dpa, damage took the form of small, isolated dislocation loops with Burgers vectors b = < 100 > and < 111 >. Loops with b = < 111 > were highly mobile, moving by discrete hops from one position to another, both during and after ion irradiation. At temperatures 300 o C and doses 1 dpa, complex microstructures developed in thicker regions of the foils. First strings of several loops, all with the same < 111 > Burgers vector formed, involving elastic interactions and cooperative movement of individual loops. Then larger loops were produced by the coalescence of loops in a string. In high-purity Fe irradiated at 300 o C, further coalescence and complex glide and climb processes led to the formation of large (several m) finger-shaped loops with b = < 111 > and large shear components. By this stage the loop nature could be shown to be interstitial. At temperatures higher than 300 o C, squareshaped sessile edge interstitial loops with b = < 100 > nucleated and grew to large sizes. At temperatures 450 o C, these < 100 > loops co-existed with < 111 > loops, but at 500 o C only < 100 > loops formed. Small voids were found at 300 o C. In this contribution these dynamical processes will be shown in the form of videos.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".