Hydrogen detrapping from grain boundaries and dislocations in high purity iron
Abstract
Hydrogen detrapping in high purity iron was studied by measuring evolution rates of quenched-in hydrogen from 80 to 800 K using a quadrupole mass spectrometer in an ultra high vacuum system. The peak of the evolution rate was observed at 395 K in single crystal specimens and 415 K in polycrystalline specimens with a heating rate of 1 K min−1. Effects of grain size and deformation on the evolution rate was also studied. It was shown that the results are consistent with the evolution rates calculated with the binding energy B = 0.51 ± 0.02 eV and the trap density term γCT = (4 ∼ 15) × 10−5 in polycrystalline iron, and B = 0.47 ± 0.02 eVand γCT = (2 ∼ 13) × 10−5 in single crystal iron. The dominant traps are considered to be grain boundaries in polycrystalline specimens and dislocations in single crystal specimens.
Résumé
On étudie le départ de l'hydrogène piégé dans un der de haute pureté en mesurant les vitesses d'évolution de l'hydrogène fixé par la trempe entre 80 et 800 K, en utilisant un spectromètre de masse quadrupolaire dans un système à ultra vide. Un pic de la vitesse d'évolution est observé à 395 K dans les échantillons monocristallins et à 415 K dans les polycristaux pour une vitesse de chauffage de 1 K min−1. Les effets de la taille du grain et la déformation sur la vitesse d'évolution sont aussi étudiés. On montre que les résultats sont en accord avec les vitesses d'évolution calculées avec une énergie de liaison et un terme de densité de pièges de B = 0,51 ± 0,02 eV et γCT = (4 ∼ 15) × 10−5 dans le fer polycristallin et de B = 0,47 ± 0,02 eV et γCT = (2 ∼ 13) × 10−5 dans le fer monocristallin respectivement. On considère que les pièges dominants sont les joints de grains dans les échantillons polycristallins et les dislocations dans les monocristaux.
Zusammenfassung
Die Freigabe von Wasserstoff aus Fallen in hochreinem Eisen wird mit der Messung der Freigaberaten des eingeschreckten Wasserstoffes zwiches 80 und 800 K mittels eines QuadrupolMassenspektrometers in einem ultrahohen Vakuum untersucht. Das Maximum der Freigaberate wird bei einer Aufheizrate von 1 K min−1 an einkristallinen Proben bei 395 K und an polykristallinen Proben bei 415 beobachtet. Der Einfluβ von Korngröβe und Verformung auf die Freigaberate wird ebenfalls untersucht. Die Ergebnisse sind verträglich mit den Freigaberaten, die sich mit einer Bindungsenergie B = 0,51 ± 0,02 eV und dem Term der Fallendichte γCT = (4 ∼ 15) × 10−5 für polykristallines Eisen und mit B = 0,47 ± 0,02 eV und γCT = (2 ∼ 13) × 10−5 für einkristallines Eisen ergibt. Als vorherrschender Fallentyp werden die Korngrenzen in polykristallinen Proben und Versetzungen in einkristallinen Proben angesehen.
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Permanent address: Department of Physics, Shimane University, 1060, Nishikawatsu, Matsue 690, Japan.