Decoding the oxidation mechanism of Zircaloy-4 via in situ synchrotron X-ray diffraction and computational elucidation
Bibliographic record
Abstract
Comprehensive understanding of the oxidation behavior of Zr alloys, a vital cladding material in nuclear power plants, is essential for developing improved materials and enhancing the safety and performance of nuclear systems. Herein, the bulk oxidation behavior in ambient air atmosphere of Zircaloy-4 were revisited through in-situ synchrotron X-ray diffraction and DFT computation. The results reveal the phase transition sequences at a representative 900 °C oxidation temperature: hcp Zr recrystallizes rapidly and then transforms into bcc Zr while reaching the α+β transus, followed by speedy appearance of textured tetragonal (t-)ZrO2, monoclinic (m-)ZrO2 and ZrN that consume oxygen and nitrogen. Continuous air ingress favors t-ZrO2 and m-ZrO2 dominance, accompanied by re-oxidation of ZrN into t-ZrO2 due to its low thermodynamic stability revealed by experiment-informed DFT calculation and low oxygen activity at the oxide-metal interface. Ensemble-averaged lattice volume expansions during phase transitions have been quantified. This expansion-induced compressive stress promotes the presence of a significant fraction of t-ZrO2 at elevated temperature that eventually transforms into m-ZrO2 during cooling.
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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 | 0.001 | 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".