POSITRON-ANNIHILATION STUDY OF IRRADIATED IRON-ALLOYS

Positron annihilation lifetime measurements and angular correlation me asurements have been performed for pure Fe and Fe alloys to investigat e the fundamental behaviors of radiation induced defects and alloying elements. It was found that Cu atoms interact with vacancies and form complexes of Cu and vacancies, which can be considered to be radiation enhanced precipitation of Cu atoms in Fe matrix. Angular correlation measurements of neutron irradiated Fe-Cr-Ni alloys and fatigued 316 ss showed that some vacancy clustering occurred. Calculation of positron annihilation lifetime was performed for a vacancy in Fe on the basis of local density approximation (LDA) with and without lattice relaxati on and showed that lattice relaxation considerably reduced the lifetim e, resulting in the reasonable fitting with the experimental value.