Elastic energy dissipation effects in the palladiumhydrogen system

Abstract

We have carried out systematic studies, over a wide range of both increasing and decreasing hydrogen contents n in the Pd- H ( PdH n ) system, of elastic energy dissipation (internal friction) peaks associated with relaxation processes arising from (1) a Zener type of effect due to stress-induced rearrangements of interstitial hydrogen and vacant interstitial sites (H (1) peak) and (2) a hydrogen-dislocation interaction effect related to the dragging of hydrogen interstitials by moving dislocations (H (2)) peak). Over the ( α + β)-phase range of n, the dependence of the relaxation strength of the H (1) peak on n has been shown to be dependent on the distribution of β-phase regions. Asymmetries of the H (1) peak in purely β-phase regions and the dependence of its relaxation strength on n have been examined and are discussed in terms of a Zener relaxation effect. The H (2) peak has not been found to be evident in β-phase regions. The height Q −1 M of the H (2) peak and its position T M on the temperature scale in α- and( α + β)-phase regions have been examined under conditions in which associated dislocation networks were introduced both by mechanical deformation and in the course of ααβ phase transitions.