POSITRON ANNIHILATION STUDY ON THE INTERACTION BETWEEN HYDROGEN ATOMS AND DEFECTS IN COLD-ROLLED NICKEL

The interaction between hydrogen atoms with defects in coldrolled nickel is investigated by Doppler broadening measurement. Experimental results show that the S-parameter in cold-rolled-hydrogen-charged nickel increases as compared with that of hydrogen-free cold-rolled nickel. And the increament of S-parameter depends on vacancy concentration, being almost independent of dislocation density. It is suggested that hydrogen atoms can act as centers of vacancy agglomeration, leading to the formation of vacancy cluster.