Cyclic plasticity of single crystal nickel oriented for single slip

The cyclic deformation behavior of single crystal nickel was investigated by performing uniaxial fully reversed constant plastic strain amplitude fatigue experiments at plastic shear strain amplitudes ranging from 1.1 × 10−4 to 8.8 × 10−3. Digitally acquired stress-strain hysteresis loops were used to calculate friction and back stresses and to relate the shapes of the loops to the evolving dislocation structures and magnetomechanical effects. The results indicate that the cyclic stress-strain curve exhibits a plateau of 50 MPa between plastic strain amplitudes of 1 × 10−4 and 7 × 10−3. Saturation friction stress, calculated using the Cottrell method, is reasonably constant over the entire range of plastic strain amplitudes at a value of 15 MPa. The back stress is 35 MPa within the plateau and increases to 48 MPa at the highest strain amplitude. When cycled at low plastic strain amplitude, magnetomechanical effects account for a significant portion of the measured inelastic strain.