(Henry B. Linford Award for Distinguished Teaching) Determination of Local Hydrogen Concentrations in High Performance Alloys Using Local Probe Methods
Notice bibliographique
Résumé
Introduction : Techniques for the measurement of hydrogen in high strength metallic alloys and effective hydrogen diffusivity (D H,eff ) lack micrometer scale spatial resolution. This is of great importance since the hydrogen-metal interactions and processes occurring at the micrometer to nanometer length scales control hydrogen embrittlement (HE). This presentation discusses three methods which enable spatial resolution and mapping of absorbed hydrogen at sub-millimeter length scales in ultra-high strength steels (UHSS) and stainless steels. The scanning Kelvin probe (SKP), scanning Kelvin probe force microscope (SKPFM), and SKP combined with secondary ion mass spectrometry have recently been developed as useful techniques for spatial H detection with depth (using cross-sectional analysis), lateral detection, and mapping.[1-7] In terms of H resolution, the SKP can detect concentrations as low as 0.01 atomic ppm.[8] This presentation explores three novel techniques for the spatial detection of hydrogen concentrations. These include the SKP, the scanning electrochemical microscope (SECM) and re-scaling methods to produce mm scale cracks or crevices that are electrochemically equivalent to small scale occluded sites [5, 9-11]. Experimental and Results : Two secondary age hardened martensitic steels were examined, UNS K92580 and UNS S46500. The SKP voltage (Φ) dependence on dissolved H concentration was optimized by mapping under conditions producing a low corrosion rate; an essential aspect of successful hydrogen mapping. A calibration curve was developed relating absorbed hydrogen concentration to Φ. High strength steels were pre-charged and exposed to MgCl 2 and NaCl droplets, which produced natural acidic pit sites that enabled local hydrogen uptake[12]. The factors controlling calibration of SKP potential and hydrogen concentration as well as those limiting spatial resolution are discussed. Moreover, D H,eff coefficients were determined.[5] Results were corroborated with previous studies of D H,eff .[13] The SECM also was optimized to enable detection of corrosion processes with spatial resolution and utilized to measure spatially a pre-dissolved concentration of hydrogen across pre-charged and uncharged zones [10]. The talk will close with comparison of the length scales of various physical processes occurring during hydrogen embrittlement compared to those accessed by these techniques. Acknowledgement: Research was sponsored by the US Air Force Academy under agreement number FA7000-13-2-0020 and ONR under PROJ0007990. The authors would like to acknowledge the Army Research Laboratories, as well as Monash University, in particular Dr. Sebastian Thomas and Prof. Nick Birbilis. The research was partially supported by a 2014 Australia Endeavour Award Research Fellowship with support from Dr. Kishore Venkatesan and Dr. Ivan Cole at CSIRO. References: [1] C. Senoz, S. Evers, M. Stratmann, M. Rohwerder, Electrochem. Commun., 13 (2011) 1542-1545. [2] S. Evers, C. Senoz, M. Rohwerder, Electrochemical Acta, 13 (2013) 1542-1545. [3] S. Evers, C. Senoz, M. Rohwerder, Sci Technol Adv Mat, 14 (2013) 014201. [4] S. Evers, M. Rohwerder, Electrochem Commun, 24 (2012) 85-88. [5] R.F. Schaller, J.R. Scully, Electrochem. Commun., 40 (2014) 42-44. [6] C. Larignon, J. Alexis, E. Andrieu, L. Lacroix, G. Odemer, C. Blanc, Electrochim Acta, 110 (2013) 484-490. [7] G. Williams, H.N. McMurray, R.C. Newman, Electrochem. Commun., 27 (2013) 144-147. [8] S. Evers, C. Senoz, M. Rohwerder, Sci Technol Adv Mat, 14 (2013). [9] B.A. Kehler, J.R. Scully, (Reprinted from Proceedings of the CORROSION/2007 research topical symposium "Advances in Environmentally Assisted Cracking", 2007), Corrosion, 64 (2008) 465-477. [10] R.F. Schaller, S. Thomas, N. Birbilis, J.R. Scully, Electrochem. Commun., 51 (2015) 54-58. [11] J.R. Scully, M. Switzer, J.S. Lee, in: S.A. Shipilov, R.H. Jones, R.B. Rebak (Eds.) Second International Conference on Environment Induced Cracking of Metals (EICM-2), Elsevier, Banff, Alberta, CA, 2008, pp. 81-93. [12] R.F. Schaller, J.R. Scully, Electrochem. Commun., 63 (2016) 5-9. [13] R.L.S. Thomas, D.M. Li, R.P. Gangloff, J.R. Scully, Metall Mater Trans A, 33 (2002) 1991-2004.
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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 | 0,001 | 0,001 |
| 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 | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 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.
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