THE INFLUENCE OF HYDROGEN AND DISLOCATIONS ON THE INTERNAL-FRICTION IN YTTRIUM

The internal friction spectra of (i) plastically deformed Y, (ii) unde formed H-doped YH0.1 and (iii) plastically deformed and H-doped YH0.1 samples were measured with the help of the vibrating reed technique (p olycrystalline foils, 5 K less than or equal to T less than or equal t o 320 K, frequencies f between 100 and 1300 Hz, plastic deformations b etween 5% and 25% due to rolling at room temperature). The deformed (u ndoped) Y samples exhibit an internal friction peak in the same temper ature range as the undeformed doped YH0.1 samples. We found further th at combined plastic deformation and H-doping leads to a stronger peak than does sole deformation or H doping. The possible mechanisms for th e observed relaxation process are discussed.