Book/Report

FZJ-2018-00371

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png The Niobium hydrogen system : an electron microscope study Part 1 : room temperature results Part 2 : low temperature structure

Schober, T. (Corresponding author)FZJ*

1975
Kernforschungsanlage Jülich, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/16517

Report No.: Juel-1160

Abstract: $\underline{Abstract (Part I)}$ The room temperature morphology of $\beta$- and $\delta$-phase precipitation in the NbH system was investigated under ultrahigh purity conditions (UHV degassed Nb and electrolytic charging). The $\beta$-phase (NbH$_{0.7}$ in the two phase region) precipitated after electrolytic charging at room temperature in the form of large, dendritic particles. Charging at 150$^\circ$ C mainly resulted in plates on {100}. The presence of domain boundaries, antiphase boundaries and twins in such precipitates was demonstrated. Evidence for extensive plastic deformation in $\beta$-phase areas was obtained andpossible reasons for this are discussed. $\delta$-phase (f .c.c. NbH$_{2}$) precipitation occurred in the form of plates on {210} inside the $\beta$-phase. Observations are presented on the $\beta$- and $\delta$-phase morphology for concentrations of up to 200 % (= H/Nb). The main reasons for hydrogen embrittlement in highly charged NbH samples are described. $\underline{Abstract (Part II)}$ The structure and morphology of low temperature hydride phases was investigated. Quenching of dilute alloys produced smallhydride particles which emitted interstitial dislocation loops into the matrix. Irreversible dislocation "skeletons" were generated when such hydride precipitates were thermally dissolved. Three ordered solutions where observed: the $\beta$-phase above -45 $^\circ$ C, the $\zeta$-phase from -45° to -65$^\circ$ C and the $\epsilon$-phase below -65°C. The reciprocal lattices of $\zeta$ and $\epsilon$ were determined. The $\epsilon$-phase is identical with the hydride Nb$_{4}D_{3}$ found by Somenkov /4, 5/. $\zeta$ and $\epsilon$ are orthorhombic with the same lattice parameters as $\beta$.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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