On the concentration dependence of the hydrogen reorientation relaxation in amorphous alloys

Abstract

The anelastic reorientation relaxation of hydrogen in amorphous alloys, only partially understood as yet, is studied with respect to its concentration dependence, using recent internal friction results on Co33Zr67 with H concentrations between about 0.001 and 1 H/metal atom as an example. Three characteristic ranges are distinguished with increasing H concentration: I. an overall growth of the relaxation peak, II. a growth with suppression of high‐activation‐energy processes, and III. the range of maximum relaxation strength. This behaviour can be understood by an increasing mutual hindering of reorientation jumps between next‐nearest neighbours (NNN) due to the local HH repulsion, which counteracts the augmentation of relaxation processes by adding more H atoms. Quantitatively, the relaxation strength can be described by adding a NNN occupation probability to the respective equation from the Berry‐Pritchet model. Most of the as yet unexplained discrepancies between different amorphous alloys can be considered formally as a shift of the ranges I to III along the H concentration scale. As the physical origin of the different behaviour, different types of inhomogeneities (e.g. a chemical decomposition) as well as intrinsic alloying effects are possible.

Hydrogen Internal Friction Peak in Amorphous Zr-Cu-Al-Si Alloys

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] One reason is that the observed relationship between T p and C H and that between Q −1 p and C H show variety among various a-alloys, suggesting that the detailed anelastic process for the HIFP is a function of the chemical composition of a-alloys. For the later-transition-metal/earlytransition-metal a-alloys, the anelastic reorientation of hydrogen atoms sitting in tetrahedral sites may be responsible for the HIFP.…”

“…The pronounced HIFP can be observed in the a-alloys which contain much hydrogen in solution, where the anelastic reorientation relaxation of hydrogen in a-alloys is responsible for the HIFP in most a-alloys. [2][3][4][5][6][7][8][9][10][11][12][13][14] A recent review for the HIFP in a-alloys com- * Graduate Student, University of Tsukuba. p data reported for metal-metal a-alloys and metal-metalloid a-alloys, where T p and Q −1 p denote the temperature and the height of the HIFP, respectively.…”

Characterization of Zr-Cu Base Metallic Glasses by means of Hydrogen Internal Friction Peak

“…(2), and redrawn on the lnðT p À T p0 Þ vs. C H plot in Figures 3(b) and 3(c), where the linear relationships between lnðT p À T p0 Þ and C H are seen. The parameters, ÁT p , H and T p0 , found for the observed data and the reported data 5,6,21,[23][24][25][26][27] for the various metallic glasses are shown in Figs. 4(a) …”

Influence of Composition and Plastic Deformation on the Hydrogen Internal Friction Peak in Amorphous Co-Zr Alloys

“…reviews . Within the general interpretation as an interstitial reorientation process (analogous to the Snoek relaxation in crystalline metals), it is still an unsolved problem how, in the disordered amorphous structure, the individual contributions of the H atoms superimpose to give the macroscopic relaxation strength and activation energy spectra [6]. Fermi-Dirac occupation statistics [7], blocking effects [g], and the interrelated distributions of atomic distances, site and saddle-point energies [9] are ingredients to this problem.…”

“…The present paper should be understood as a first step to provide such systematic data, in preliminary form, on both of these aspects. The system CO-Zr has been chosen because extensive results on the hydrogen relaxation already exist for the composition C O~~Z~~~ [5,6,13,14].…”