Investigating the Microstructural Stability of Nanocrystalline Oxide Dispersion-Strengthened Alloys under Proton Irradiation by X-ray Line Profile Analysis
Notice bibliographique
Résumé
Nanocrystalline (NC) alloys contain unique defect structures compared to conventional Coarse-Grained (CG) alloys. NC alloys have smaller grains, and therefore higher Grain Boundary (GB) volume fraction, higher dislocation density and more ordered dislocation structures. Experimental and computational studies of NC alloys show improved resistance to degradation of material properties under irradiation due to increased point-defect (PD) sink densities. As a result, there is a reduced concentration of PDs available for clustering into higher-dimensional defects, which are chiefly responsible for the degradation of properties at the engineering scale. This work aims to experimentally validate the approach of limiting radiation damage by introducing pre-existing defect structures, as well as to gain a better understanding of the defect interactions that govern the thermodynamics and kinetics of irradiation-induced microstructural evolution. A Ni-based superalloy (Inconel 617, solution-annealed and aged) and two Oxide Dispersion-Strengthened (ODS) alloys, Ni and Fe-based (MA754 and MA957), are processed by High-Pressure Torsion (HPT), a form of Severe Plastic Deformation (SPD). Convolutional Multiple-Whole Profile (CMWP) analysis of high-resolution Xray diffraction (XRD) patterns reveals these sample to have dislocation densities on the order of 1016 m-2 and crystallite sizes of approximately 15 nm. Following low temperature (T < 0.35Tm) proton irradiation up to two displacements per atom (dpa), XRD experiments are repeated. Irradiation is found to cause partial annihilation of the dislocations created by HPT, with the mechanism of dislocation annihilation seemingly depending on crystal structure. Irradiation-induced grain growth, thought to be due to cascade-induced thermal spikes overlapping with grain boundaries, is observed in all samples. However, Inconel 617 exhibits “NC stability”, exemplified by a stable grain size with increasing dose – the greater NC stability of Inconel 617 agrees with earlier differential scanning calorimetry recrystallization experiments. XRD phase analysis suggests that the nanoscale oxide dispersions in MA754 and MA957 undergo ballistic dissolution due to low-temperature irradiation. Thus, they are unable to exert a Zener pinning force on mobile GBs to improve NC stability, nor can they serve as effective recombination sites for PDs, indicating that NC-ODS alloys do not show significant promise in the pursuit of material stability in extreme environments. The results suggest that NC stability is better approached by finetuning the alloy system to reduce GB energy. Finally, the irradiation-induced precipitation of α-Cr is found to occur in all Ni-based samples, with the effect being far more prevalent in MA754. Experimental evidence for radiation-induced segregation occurring concurrently with grain growth (previously investigated via phase-field models) is presented, with XRD revealing a grain size dependence on Cr concentration.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».