MEASUREMENTS OF VACANCY TYPE DEFECTS IN SPD DEFORMED NI

摘要

Ni of different purities have been deformed by severe plastic deformation (SPD) i.e. high pressure torsion (HPT) at different hydrostatic pressures. The results are being compared with previous investigations on conventionally deformed Ni. In order to quantitatively conclude the concentration of vacancy type lattice defects, calorimetric investigations have been carried out. It turns out that the concentration of vacancies being present after SPD deformation markedly exceeds that one after conventional plastic deformation. For highly pure Ni, not only vacancy agglomerates but also single and double vacancies have been identified which anneal at a much lower temperature. Similar to the case of Cu, the concentrations of all vacancy type defects depend on the deformation strain as well as on the hydrostatic pressure applied during SPD.