Vacancy production during plastic deformation in copper determined by in situ X-ray diffraction

The discrepancy between stored energies measured by calorimetry and residual electrical resistivity, and calculated from dislocation densities measured either by transmission electron microscopy or X-ray line broadening in copper, is interpreted in terms of vacancies produced during plastic deformation. The presence of excess vacancies is further substantiated by concomitant measurements of residual electrical resistivity. Diffuse X-ray scattering is correlated with excess vacancy concentrations in the grain interior and grain boundary regions in polycrystalline copper. Grain boundaries are suggested to be the main sites for vacancy storage probably in the form of voids or free volume. This would support the concept that grain boundaries are distorted regions with considerable fractions of free volume. The vacancy storage rate is shown to depend on the mode of deformation.