Deformation behavior during thermo-mechanical fatigue of a nickel-based single crystal superalloy

The deformation and damage mechanisms of a single crystal nickel-based superalloy CMSX-4 have been investigated under out-of-phase thermo-mechanical fatigue (OP TMF) condition. The failure mechanism was oxide-layered surface initiated crack followed by its planar growth along <100> γ channel. However, the deformation was highly localized to area near crack tip, where multiple groups of parallel twin plates on {111} planes formed during the high temperature-compressive half cycle. The localized twins provided a preferential path for crack propagation. OP TMF deformation was dominated by partial dislocation movement with {111}<112> slip system, resulting in the formation and propagation of deformation twins.