The discrepancy between the stored energies measured by calorimetry and residual electrical resistivity, and those deduced from the dislocation densities measured by transmission electron microscopy or X-ray line-broadening, was interpreted in terms of the vacancies produced during plastic deformation. The presence of excess vacancies was confirmed by concomitant measurements of residual electrical resistivity. Diffuse X-ray scattering was correlated with excess vacancy concentrations in the grain interior and grain-boundary regions in polycrystalline Cu. The grain boundaries were 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 were distorted regions comprising considerable fractions of free volume. The vacancy storage rate was shown to depend upon the mode of deformation.

Vacancy Production during Plastic Deformation in Copper Determined by In Situ X-ray Diffraction. T.Ungár, E.Schafler, P.Hanák, S.Bernstorff, M.Zehetbauer: Materials Science and Engineering A, 2007, 462[1-2], 398-401