PECULIARITIES OF SOLID-SOLUTION DECAY OF HYDRIDE-FORMING AND NON-HYDRIDE-FORMING SYSTEMS WITH CLOSE-PACKED CRYSTAL-STRUCTURE

The most precise structure-sensitive methods (electron-positron annihi lation, electroresistivity and internal friction measurements) yield f or the existence of hydrogen-induced lattice vacancies, and hydrogen-s timulated diffusion in HCP and FCC Me-H systems which were accompanied by the formation of ''H atom-excess (nonintrinsic) vacancy'' pair def ects (clusters). A new method for analysing the high-temperature depen dence of Me-H system electroresistivity and a model for clusterization of the structure in solid solutions of Me-H, oversaturated with exces s 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 di ffusion in hydride-forming Systems (Ti-H, Zr-H). Thermally activated a ssociation of clusters with high bonding energy (0.5-0.6 eV) was found to be a controlling mechanism for hydrogen-stimulated diffusion in no n-hydride-forming systems (Al-H). Clusterization of excess defects sim plifies formation of hydrides at significantly lower temperature. Copy right (C) 1996 International Association for Hydrogen Energy.