Low cycle fatigue of a Ni-based superalloy: Non-planar deformation

Cyclic softening is observed in the polycrystalline Ni-based superalloy R104 at elevated temperatures. Using transmission electron microscopy characterization methods, the damage evolution in fatigued specimens was studied. The observed deformation modes include paired APB shearing, intense planar dislocation bands, and cross-slipping processes between {1 1 1} and {0 0 1} planes. A rationale for the observed mechanisms in terms of time-dependent damage processes will be discussed.