(Invited) In-Situ Liquid Phase TEM Studies of Corrosion Initiation in Aluminium Alloys
Notice bibliographique
Résumé
Aluminium alloy 2024-T3 (AA2024-T3), widely applied in aerospace industries, may suffer from severe localized corrosion as a result of its relatively complex and heterogeneous microstructure. The corrosion initiation in such a critical alloy is governed by dynamic processes that take place at the nanoscale. A thorough understanding of the sequential stages of corrosion initiation is of pivotal importance to developing efficient inhibition strategies and demands high resolution techniques along with the ability of real-time recording of nanoscopic events. However, to date, it has not yet been possible to unambiguously show the morphological and electrochemical characteristics during local corrosion of AA2024-T3. In particular, local corrosion initiation linked to nano-/microstructural heterogeneities, intermetallic particles (IMPs), take place relatively fast and at the nanoscopic scale, rendering the study of the early stages of corrosion experimentally virtually impossible until now. Herein, we show, for the first time, the dynamic evolution of site-specific local corrosion of AAs from early surface initiation to depth propagation at the nanoscale using a dedicated in-situ liquid phase-transmission electron microscopy (LP-TEM) experimental facility. Transmission electron microscopy (TEM), capable of revealing microstructural and compositional variations in alloys at atomic and nanoscopic scale, has been applied widely in corrosion studies but mostly ex-situ and quasi in-situ. These approaches are not straightforward as artefacts and contaminations might be introduced into the system during the ex-situ and quasi in-situ experiments, including dehydration of surfaces and therefore may not fully represent the real conditions. With recent technological advances, thanks to the development of dedicated microelectronic mechanical systems (MEMS), it is now possible to fabricate components like nanoreactors (NRs) to study complicated corroding systems at the nanoscale in-situ. In fact, NRs employed in TEM studies enable to monitor morphological and compositional evolutions in materials in-situ as a result of interaction with aggressive environments like a gas or liquid. In this study, we put efforts into providing direct evidence for the nanoscopic role of intermetallics in AA2024-T3 localized corrosion through quasi in-situ TEM and in-situ LP-TEM approaches. Quasi in-situ studies were implemented by intermittently exposing the Argon ion-milled thin samples to 0.01 M NaCl solution. For in-situ LP-TEM, the real TEM specimens (lamellae) were first fabricated out of regions of interest with a FEI Helios focused ion beam. Then, the lamellae were transferred successfully to home-made NRs using an easy-lift technique. The NRs, equipped with an electrochemical set-up, were specially designed for corrosion studies. A Cs-corrected FEI Titan TEM was employed to perform real-time studies in scanning TEM (STEM) mode. Although a good resolution is still a major challenge for in-situ LP-TEM, the results revealed that intermetallic phases regardless of their types are active and prone sites to localized corrosion attack themselves and the observations finally show and elucidate initial stages of IMP-induced pitting corrosion and copper redistribution mechanisms in AA2024-T3.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,016 | 0,009 |
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 source (Gemma direct ou Codex distillé), 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 ».