Vacancies in plastically deformed copper

In discussing hardening characteristics in terms of crystalline lattice defects, in most cases the properties and kinetics of dislocations and their arrangement have been considered. However, during plastic deformation also vacancies and/or vacancy-type defects are produced in very high densities which are typically close to those of vacancies in thermal equilibrium at the melting point. This paper presents measurements of deformation-induced vacancies in deformed copper which have been achieved by combined evaluation of resistometry, calorimetry and X-ray diffraction. The density of vacancies during and after severe plastic deformation (SPD) deformation is found to be markedly higher than in cases of conventional deformation and/or coarse-grained material, which is attributed to the particular conditions of SPD, i.e., the enhanced hydrostatic pressure as well as the changes in the deformation path. The use of synchrotron radiation allows to apply the XPA method for in-situ deformation monitoring of intrinsic structural parameters. This also includes deformation-induced vacancies, evaluated by the diffuse background of Bragg peak profiles.