Lattice defect investigation of SPD metals by means of X-Ray line profile analysis and electrical residual resistivity

Ni and Ti have been subjected to different modes of SPD (ECAP, HPT). Deformation induced defects such vacancies dislocations and local internal strains have been studied with Residual Electrical Resistivity (RER) and X-Ray Line Profile Analysis (XPA). The densities and arrangements of defects have have been measured as a function of deformation degree and - in case of HPT - extent of hydrostatic pressure. It has been found that both the vacancy consentrations and the dislocation densities are higher than with usual deformation like torsion, compression and rolling and that they still increase with increasing deformation degree as well as increasing hydrostatic pressure. For both quantities, however a saturation has been observed with respect to deformation and hydrostatic pressure applied. With the help of measurement of internal strains, the saturation effect is discussed in terms of static and dynamic recovery.