Homogeneity of ultrafine-grained copper deformed by high-pressure torsion characterized by positron annihilation and microhardness
2011
Abstract
Spatially resolved positron annihilation was employed for mapping lateral defect distribution in Cu deformed by high-pressure torsion. Parameters describing Doppler broadening of the annihilation peak were used for mapping the spatial distribution of defects.
In comparison with microhardness showing a clear development towards homogeneity, positron annihilation revealed that spatial distribution of defects was far from uniform, even after 25 turns. This was mainly due to a higher concentration of deformation- induced vacancies at the periphery compared with the center.