Localized microtwin formation and failure during out-of-phase thermomechanical fatigue of a single crystal nickel-based superalloy

Abstract The deformation and damage mechanisms of a single crystal nickel-based superalloy CMSX-4 have been investigated under out-of-phase thermomechanical fatigue (OP TMF) condition. The deformation was highly localized to the area near the crack tip, where multiple groups of parallel twin plates on {1 1 1} planes formed during the high temperature-compressive half cycle. The atomistic a/6 〈1 1 2〉 twinning shear-based approach is presented which explains the origin of twinning. The localized twins provided a preferential path for crack propagation. OP TMF deformation was dominated by partial dislocation movement with {1 1 1}〈1 1 2〉 slip system, resulting in the formation and propagation of deformation twins.