Abstract
In austenitic stainless steels, an internal friction peak caused by dissolved hydrogen has been found and attributed to a Snoek-type relaxation of hydrogen atom complexes in the FCC lattice. However, much of the structure of the complexes remains unknown because no precise data are available on the dependence of relaxation strength on hydrogen concentration in austenitic stainless steels. On the other hand, Fe-35%Ni Invar alloy is known to form a similar internal friction peak with more sufficient relaxation strength even by the gas equilibration method of hydrogen charging. The hydrogen peak of internal friction is confirmed in the Fe-35%Ni alloy containing 30∼320 at ppm hydrogen. The peak position is around 250 K at about 700 Hz. The peak height increases monotonously with increasing hydrogen concentration but shows a complicated tendency when plotted against hydrogen concentration. However, the peak height appears to increase parabolically with low hydrogen concentrations from 0 to 100 at ppm. This fact suggests that hydrogen atom pairs are most likely to contribute as the corresponding complexes to the hydrogen peak of internal friction in FCC iron alloys.
