Positron Annihilation in Metals Defected by Action of the Tensile Force

Results of experimental investigations of uniaxially elongated mono- and polycrystalline samples of several metals (Fe, Ta, Pd, Ag, and Au), performed using the positron annihilation methods, are reviewed. The dependences of the S-parameters and positron lifetimes on the relative elongation of the samples were presented. The data obtained for polycrystalline samples indicate that in the proportionality and limited proportionality regions the changes in the physical properties are governed mainly by generation of vacancies and by kinetics of formation and transformations of vacancy clusters occurring first of all on the grain boundaries of monocrystallites. In the region of plastic deformations the dominant defects are dislocations and vacancies and their aggregates generated due to the formation and movement of the dislocations of the primary and secondary slip. In the case of monocrystalline samples it was found that the dynamics of the dislocations and vacancy generation during the sliding of some crystallographic planes depends on the crystallographic direction.