Anelasticity of polycrystalline Y at low concentrations of H and O

In order to clarify the nature of the numerous thermally activated processes occurring in yttrium, the anelastic relaxation spectrum of polycrystalline samples has been investigated between 1.1 and 600 K in the kHz range, by varying the concentration of interstitial hydrogen and oxygen and in presence of plastic deformation. Besides the main dissipation peak around 300 K due to the formation/dissolution of H pairs and the peak at liquid He temperature attributed to H tunnelling, four processes have been observed. The processes below 300 K can be interpreted by mechanisms involving hydrogen trapped by oxygen, and dislocations dragging interstitial H, whilst the large relaxation observed around 450 K has to be ascribed to oxygen motion in solid solution.