Peculiarities of solid solution decay of hydride-forming and non-hydride-forming systems with close-packed crystal structure

Abstract

The most precise structure-sensitive methods (electron—positron annihilation, electroresistivity and internal friction measurements) yield for the existence of hydrogen-induced lattice vacancies, and hydrogen-stimulated diffusion in HCP and FCC Me-H systems which were accompanied by the formation of “H atom—excess (non-intrinsic) vacancy” pair defects (clusters). A new method for analysing the high-temperature dependence of Me-H system electroresistivity and a model for clusterization of the structure in solid solutions of Me-H, oversaturated with excess vacancies were developed. It was established that partial thermally activated dissociation (decay) of clusters with low bonding energy (0.2 eV) appears to be a controlling mechanism for hydrogen-stimulated diffusion in hydride-forming systems (Ti-H, Zr-H). Thermally activated association of clusters with high bonding energy (0.5-0.6 eV) was found to be a controlling mechanism for hydrogen-stimulated diffusion in non-hydride-forming systems (AlH). Clusterization of excess defects simplifies formation of hydrides at significantly lower temperature.