Research on low cycle fatigue damage and macroscopic anisotropic constitutive model of Ni-based single crystal superalloy at different temperatures

Ni-based single crystal superalloys are extensively utilized in the turbine blades of aeroengines and gas turbines. Although there has been considerable research on the low cycle fatigue (LCF) behavior of single crystal at various temperatures, there is currently no universally damage coupled model for characterizing damage and failure modes at different temperatures. In this study, LCF behavior of a second-generation Ni-based single crystal superalloy was researched at room temperature, 700 °C, 800 °C, 900 °C and 1000 °C. The experimental results illustrated remarkable differences in the LCF behavior at different temperatures. Fracture modes exhibited distinct ductility characteristics at room temperature and high temperatures (900 °C and 1000 °C), whereas at medium temperatures (700 °C and 800 °C), quasi-brittle fracture along the octahedral slip system became dominant. A cumulative damage coupled constitutive model was developed to simulate the damage evolution of single crystal superalloys during LCF loading. The simulation results show that the proposed model can effectively predict the damage evolution at different temperatures, especially the damage index ζ corresponding to the same damage mode.