Point defects in push-pull fatigued nickel polycrystals

The generation and localization of point defects in room-temperature push–pull fatigued nickel polycrystals is investigated by recovering the electrical excess resistivity in dependence on mechanical parameters. Recovery stages at 390 and 525 K can be associated to monovacancy migration in the regions of higher and lower dislocation density, respectively. The vacancy concentrations in the stabilized state at constant total strain amplitude of ϵa = 3 × 10−3 are found to be cwv = = 4 × 10−5 and ccv = 5 × 10−6 in these regions. Above a certain number of cycles a new kind of sink, whose generation depends on the vacancy concentration begins to act. In the course of intermediate annealing experiments these sinks are indentified to be vacancy clusters.