Effect of dynamic recovery on structure formation in nickel upon high-pressure torsion and subsequent annealing

Experiments on single-crystal nickel (99.98%) subjected to high-pressure torsion at a pressure of 6 GPa and room temperature to the true strain е=10 (10 anvil revolutions) served to reveal the influence of dynamic recovery on the formation of the most fine-grained structure both in the course of deformation and upon subsequent annealing. Dynamic recovery leads to gaining a stationary deformation stage that is characterized not only by unchangeable values of hardness (3.4 GPa) and structure-element size (130 nm), but, first of all, constant amount of the stored energy of deformation. A relation of the staged character of structure changes in nickel upon deformation with temperature and kinetics of recrystallization has been established. The process of recrystallization at temperatures lower than the temperature of formation of thermally activated recrystallization nuclei is developed as a discontinuous process of growth of individual centers created in the course of deformation.