A comparative study of low cycle fatigue behavior and microstructure of Cr-based steel at room and high temperatures

Abstract

The effect of temperature on tensile behavior, low cycle fatigue, and microstructure evolution considering the damage mechanisms of Cr-based heat-resisting steel was investigated. The results present that significant monotonic and cyclic softening was observed at both room temperature and 630 °C. However, the cyclic softening factor is independent of the strain amplitudes and temperatures. At room temperature, the steady fatigue behavior until 80% fatigue life was presented, by contrast, great changes were offered below 80% fatigue life at 630 °C. this is directly related to the microstructure properties during fatigue tests, where dislocation network, wall, and dynamic recovery were formed, resulting from the dislocation movement, interaction, and annihilation. The density of dislocation and intensity of slip is inversely proportional to the temperature. Besides, a prediction fatigue life model fitted by the quadratic function was established through the hysteresis energy, which can consider the effect of temperature on the different fitting parameters and offer the method to optimize the fatigue behavior of Cr-based steel at different temperatures