Design criteria for single-phase non-equiatomic refractory multiprincipal element alloys from the Nb-Ti-Zr system
Bibliographic record
Abstract
• Design criteria for stable, single-phase refractory high entropy alloys from Nb-Ti-Zr system are established. • Combinational synthesis enabled screening through large portion of the Nb-Ti-Zr system. • Dissolved oxygen is the primary factor destabilizing the desired single-phase BCC structure. • Ti-rich compositions had higher oxygen tolerance than Zr-rich ones, despite similar oxygen solubility. Refractory high entropy alloys (RMPEAs) hold promise as candidate materials for high-temperature applications challenging widely used nickel-based superalloys. RMPEAs application is currently limited by their low structure and phase stability in the presence of oxygen, which can be improved by single-phase alloy design. This study establishes design criteria for achieving single-phase, non-equiatomic RMPEAs through a systematic exploration of the Nb-Ti-Zr compositional space. Using combinatorial synthesis via magnetron co-sputtering and high-throughput characterization, we map phase stability across a broad compositional range. We identify a stable single-phase BCC region for compositions containing 19.5–55 at.% Nb, 43–59 at.% Ti, and less than 30.5 at.% Zr. Monte Carlo simulations were used to predict the phase formation at high temperatures along with electron microscopy revealing phase segregations at high-Zr compositions, exploring the role of soluble oxygen in phase formation. Our findings provide a foundation for the rational alloy design, explain the effect of each element, and pave a path for further exploration and modification of the identified compositional space.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".