Effect of rhenium on low cycle fatigue behaviors of Ni-based single crystal superalloys: a molecular dynamics simulation

Abstract

Molecular dynamics simulations are carried out to investigate the effects of rhenium (Re) on low cycle fatigue behaviors and deformation mechanisms of Ni-based single crystal superalloys. The low cycle fatigue behaviors and deformation mechanisms at different temperatures are discussed. The results show that Re has a positive effect on the low cycle fatigue behaviors of Ni-based single crystal superalloys and the cyclic deformation mechanism is strongly dependent on temperature, which are in good agreement with the previous experimental results. The addition of Re can increase the saturation stress amplitude, reduce the cyclic hysteresis energy and dislocation density, and improve the plastic deformation resistance of the superalloys. During cyclic loading, Re atoms in γ matrix phase gradually move to the γ/γʹ interface, these enrichment of Re atoms at the γ/γʹ interface have pinning effect on dislocations, improving the microstructure stability. At the later of the saturation cycle, segregations of Re atoms prevent the dislocations from cutting into the γ′ phase by dragging dislocations, thus improving the fatigue resistance of superalloys. The simulation results also show that the deformation mechanism gradually changes from dislocations and stacking faults shearing γʹ precipitate phase to Orowan bypassing and climbing mechanism with temperature increases.