Back‐Stress‐Stored Energy‐Based Very High Cycle Fatigue Crack Initiation and Life Prediction of GH4169 With Microstructure‐Temperature Effects

Nickel‐based superalloy GH4169, critical for aero‐engine hot‐section components, exhibits distinct very high cycle fatigue failure mechanisms across temperature regimes. Systematic investigation integrating fatigue experiments, microstructural characterization, and crystal plasticity simulations reveals that at room temperature (RT), subsurface cracks initiate via transgranular cleavage along twin boundaries (TBs), governed by γ″‐denuded zones and slip bands parallel to TBs (Schmid factor > 0.45). At 650 °C, crack nucleation shifts to interfaces of Ti/Nb‐segregated hard particles (HPs), where thermomechanical mismatch and dislocation pile‐ups drive interfacial fracture. A novel fatigue indicator parameter—back‐stress‐stored energy density ( G _ba )—quantitatively captures both mechanisms: TB‐adjacent slip localization (RT) and HP‐induced strain incompatibility (650 °C). By correlating G _ba accumulation with the material's intrinsic fracture energy, a physics‐based life prediction model is established. Predictions for RT and 650 °C achieve 94.7% accuracy within ±3.5 scatter, advancing safety assessment for high‐temperature components.