Hydrogen Internal Friction Peak in Amorphous Cu50Zr50

Effects of annealing at 423 K and deformation on the hydrogen internal friction peak (the H-peak) in the H-concentration, CH, below 32 at%, and the thermal desorption spectrum, TDS, for CH below 46 at% are investigated on amorphous Cu50 Ti50 (a-CuTi). The results for the H-peak suggest the following: in a-CuTi, only H-atoms occupying the interstitial sites with G ≒ μ in N(G) can contribute to the H-peak, where N(G) denotes the site energy, G, distribution and μ the chemical potential of the H-atoms in the specimen. N(G) is composed of Gaussian distributions N1(G) for CH ≦ 12 at%, N2(G) for 9 ≦ CH ≦ 35 at%, and N3(G) for CH ≧ 28 at%. N1(G) to N3(G) are surmised to correspond to the 4 Ti, 3 Ti + 1 Cu, and 2 Ti + 2 Cu tetrahedral sites, respectively. From these results combining with the near-neighbor blocking model for the H occupation, it is surmised that in a-CuTi, the H-peak is associated with H atoms within the rather large clusters of the tetrahedra of the same chemical composition. From TDS, g* − G3,0 ⪅ 0.5 eV/H-atom, g* − G2,0 ⪆ 0.8 eV/H-atom, and g* − G1,0 > g* − G2,0 are estimated, where Gi,0 denotes the mean, G, for Ni(G), g* the transiet state to form a H2-molecule at the specimen surface. The H-peak profile reflects an activation energy (E) distribution n(E; μ) in N(μ). For all Ni(G), ni(E; G) in Ni(G) is composed of six constituent Gaussian distributions CGD's. Annealing and deformation do not change the outlines for Ni(G) and ni(E; G) except that annealing often causes a strong increase of the H-peak as a whole for 6 ≦ CH ≦ 14 at% which appears to be canceled by subsequent deformation. For CGD's, annealing gives rise to the complementary increase in CGD-1 and decrease in CGD-2 for CH at around 7 at% which remains unchanged after subsequent deformation. These results suggest that the as-prepared state is different from the deformed state. Temperungs- und Deformations-Einflusse auf das Maximum der inneren Reibung von Wasserstoff (H-Maximum) bei H-Konzentrationen CH, unterhalb 32 At%, und das thermische Desorptionsspektrum TDS, fur CH unterhalb 46 At% werden an amorphem Cu50 Ti50 (a-CuTi) untersucht. Die Ergebnisse fur das H-Maximum ergeben folgendes: in a-CuTi konnen nur H-Atome, die die Zwischengitterplatze mit G ≒ μ in N(G) zum H-Maximum beitragen konnen, wobei N(G) die Verteilung der Platzenergie G und μ das chemische Potential der H-Atome in der Probe bezeichnet. N(G) ist aus Gausverteilungen N1(G) fur CH ≦ 12 At%, N2(G) fur 9 ≦ CH ≦ 35 At% und N3(G) fur CH ≧ 28 At% zusammengesetzt. Es wird vermutet, das N1(G) bis N3(G) mit den 4 Ti-, (3 Ti + 1 Cu)- bzw. (2 Ti + 2 Cu)-Tetraederplatzen korrespondiert. Aus diesen Ergebnissen zusammen mit dem Blockingmodell nachster Nachbarn fur die H-Besetzung wird vermutet, das in a-CuTi das H-Maximum mit H-Atomen assoziiert ist in den ziemlich grosen Clustern der Tetraeder mit derselben chemischen Zusammensetzung. Aus dem TDS wird g* − G3,0 ⪅ 0,5 eV/H-Atom, g* − G2,0 ⪆ 0,8 eV/H-Atom und g* − G1,0 > g* − G2,0 berechnet, wobei Gi,0 den Mittelwert G fur Ni(G) bezeichnet und g* der Ubergangszustand, um ein H2-Molekul an der Probenoberflache zu bilden. Das H-Maximumprofil spiegelt eine Aktivierungsenergie (E)-Verteilung n(E; μ) in N(μ) wieder. Fur alle Ni(G) ist ni(E; G) in Ni(G) aus sechs Konstituenten-Gausverteilungen (CGD) zusammengesetzt. Temperung und Deformationen andern nicht die Umrisse fur Ni(G) und ni(E; G) auser das Temperung oft einen starken Anstieg des H-Maximums insgesamt fur 6 ≦ CH ≦ 14 At% verursacht, der bei nachfolgender Deformation zu verschwinden scheint. Fur die CGD gibt Temperung Anlas zu einem komplementaren Anstieg in CGD-1 und Abfall in CGD-2 fur CH bei etwa 7 At%, die nach darauffolgender Deformation ungeandert bleibt. Diese Ergebnisse weisen darauf hin, das der ursprunglich praparierte Zustand vom deformierten Zustand verschieden ist.

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