A. Zielinski et al., INTERNAL-FRICTION IN COLD-WORKED AND HYDROGEN CHARGED NICKEL SINGLE-CRYSTALS, Zeitschrift fur Metallkunde, 87(2), 1996, pp. 104-110
Internal friction measurements were performed on plastically pre-defor
med ultrapure nickel single crystals. Bordoni and Niblett-Wilks relaxa
tion was observed. From the activation enthalpy of the Bordoni relaxat
ion, H-eff(B) (0.19 +/- 0.03) eV, the enthalpy of a single kink could
be derived as H-k = 0.093 eV applying Seeger's kink-relaxation model.
After the measurements under hydrogen-free conditions, the specimens w
ere charged with hydrogen from gaseous phase or electrolytically. Thus
, rather different hydrogen concentrations were obtained. The hydrogen
loading caused an intense Snoek-Koster relaxation while the Bordoni r
elaxation vanished nearly completely. The experiments indicate an infl
uence of the hydrogen concentration along the dislocation lines on the
activation enthalpy of the Snoek-Koster relaxation which was found as
H-eff(SK) = (0.59 +/- 0.06) eV on electrolytically charged specimens.