Characterizing microstructural evolution and low cycle fatigue behavior of 316H austenitic steel at high-temperatures

Abstract

This study investigates the relationship between the microstructural evolution and low cycle fatigue behavior of 316H austenitic steel to understand its performance at 550°C in generation-IV nuclear power plants. The 316H steel exhibited non-Masing behavior, where the cyclic hardening behavior followed by cyclic softening behavior was presented. The increased strain amplitude led to a higher degree of cyclic softening, which was related to the evolution of dislocation structures during cyclic deformation under different strain amplitudes. Cells appeared at high strain amplitudes and had poor plastic deformation resistance as compared with the wall structures at lower strain amplitudes, resulting in the highest degree of cyclic softening at high strain amplitude. Dynamic recrystallization could be fully achieved under low strain amplitude, resulting in a greater decrease in dislocation density and increased generation of new, undistorted grains. Additionally, this caused the cyclic softening behavior. Moreover, a modified life prediction model based on plastic strain energy was employed to predict the fatigue life of 316H steel.