The lattice defects introduced by the initial hydriding were studied by means of positron lifetime spectroscopy and H thermal desorption measurements. A component analysis of 

the positron lifetime spectra showed that surprising numbers of vacancies, together with dislocations, were generated by the initial hydriding. Vacancy migration, after H desorption at room temperature, was observed at 423 to 673K. The dislocations were much more stable. Thermal desorption measurements showed that the release of residual H occurred mainly at 450 to 650K, and ceased at about 800K. The release temperature of residual H closely corresponded to the temperature of vacancy migration and annihilation. Residual H was suggested to be most probably trapped by vacancies and vacancy clusters which were introduced by hydriding.

Recovery of Hydrogen-Induced Defects and Thermal Desorption of Residual Hydrogen in LaNi5. K.Sakaki, H.Araki, Y.Shirai: Materials Transactions, 2002, 43[7], 1494-7