The recovery of H-induced defects in post-deformation H-charged polycrystalline material was studied by using Doppler-broadening line-shape parameter measurements. The recovery behavior of defects in H-charged samples was changed by the accumulation and release of H and by the fact that H could act as nuclei for vacancies. The recovery of vacancies occurred at temperatures ranging from 75 to 260C, and the recovery of dislocations and vacancy clusters occurred at temperatures above 350C. The measured activation energy for the migration of mono-vacancies was 1.09eV. The hexagonal close-packed to face-centered cubic transition created a non-equilibrium defect population which was capable of trapping positrons. Positron Annihilation Studies of Hydrogen-Induced Defects in Post-Deformation Hydrogen-Charged Polycrystalline Cobalt. D.Peng, T.Wang, Z.Tong: Physica Status Solidi A, 1993, 135[1], 103-8