Recovery of deformed and hydrogen-charged palladium

Positron lifetime and Doppler-broadening studies made at 300 K have been used to investigate the interaction between interstitial hydrogen and lattice defects in deformed Pd. Specimens were charged with hydrogen at 300 K to levels up to 0.1%. The presence of hydrogen was found to have no effect on the recovery curves of Pd upon annealing to 4000C. By 4000C the values for both lifetime and Doppler-broadening for both cold worked and cold worked plus hydrogen were below the values obtained for annealed pure Pd. This can be interpreted as gaseous-impurity-trapped vacancies being present after the 12000C anneal, but being swept away by the dislocation microstructure recovery between 200-4000C. Although the specimens hydrided to the #betta# phase and outgassed back to the α phase showed continual recovery up to 4000C, complete recovery was not achieved as with the deformed specimens. The lifetime results indicate the presence of defects more open than single vacancies. One possibility would be the formation of cavities, possibly hydrogen filled, during the hydriding that are stable at 4000C. (Auth.)