Microstructural Evolution Behavior and Deformation Mechanism of Notched Components at Elevated Temperatures Under Fatigue Loadings

The significant strain accumulation in structural discontinuities may accelerate the fatigue failure of components at elevated temperatures, and understanding the microstructural evolution features and deformation mechanisms in these localized regions is essential for the accurate structural integrity assessment. In this work, the high‐temperature fatigue behavior of 316H steel was investigated on notched specimens with different root radii. A comprehensive EBSD microstructural analysis was performed to elucidate the correlation between the fatigue behavior and microstructural evolution. The fatigue life prediction of notched components based on the theory of critical plane was conducted. The results indicated that the introduction of notches significantly alters both the cyclic softening and hardening features and the average ratcheting strain behavior of 316H steel. The deformation mechanism at the notch section transitions from the slip for a blunt notch to twinning formation for a sharp notch. The secondary hardening phenomenon observed in specimens with sharp notches results from the strengthening effect of the twinning.