Abstract
Internal friction was measured at constant temperature as a function of frequency from 10−3 Hz to 10 Hz in austenitic stainless steel charged with hydrogen. A relaxation peak due to hydrogen was detected in the frequency dependence of internal friction measured around 200 K, where such a peak has not yet been reported. This peak apparently corresponded to the well-known hydrogen peak found so far in the temperature dependence of internal friction. The activation energy of the hydrogen peak was estimated by the peak-shift method to be 53.7 kJ/mol, which agrees well with the activation energy of hydrogen diffusion in austenitic stainless steel.
Hydrogen-charging was carried out by the electrolytic method and also by the gas-equilibration method. Both the methods always produced a hydrogen peak of internal friction, although the austenitic phase transformed partially to a hydrogen-induced εH phase by the former method but not at all by the latter method. Therefore, the hydrogen peak was not associated with any hydrogen-induced transformation. This fact leads to the conclusion that the hydrogen peak is caused by dissolved hydrogen in the fcc lattice of austenitic stainless steel and it may probably originate from the stress-induced ordering of hydrogen atom pairs or clusters.
