Positron Annihilation in Polycrystalline Metals Deformed by Uniaxial Tension

Angular distributions of the positron annihilation quanta were measured for polycrystalline samples deformed by uniaxial tension up to different deformation degrees. The S parameter as a function of the W parameter was determined. The data obtained for samples elongated up to different elongation degrees indicate that in the proportionality and limited proportionality regions the changes in the physical properties of samples are governed mainly by generation of vacancies and formation and kinetics of transformations of vacancy clusters occurring first of all on the grains 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 dislocation of the primary and secondary slip. The positron annihilation data are corroborated by the results of the resistometric and tensometric measurements in the proportionality and limited proportionality regions.