Cyclic microstructure analysis, crack propagation and life prediction of Inconel 750H considering the slip fracture energy

Abstract

The cyclic stress responses and microstructure analyses were carried out of short-term aged Inconel 750H under high temperature low cycle fatigue tests, the influence of strain amplitude on fatigue fracture mechanism of aged IN 750H was systematically analyzed. According to the slip traces, Schmid factor, and geometrically necessary dislocation density distribution on the fracture frontier, the paper revealed that the local slip band provided a preferred path for the fatigue crack growth of Inconel 750H. Due to the limitation of the inability to measure energy of slip system through experiments, a probability based statistical method on average fracture energy of the slip system was constructed. Coupling with the macro-scale constitutive models, a microstructural-sensitive strategy based on fracture energy exhaustion theory was established. Based on the proposed model, the dynamic process of fatigue crack initiation and growth stage were simulated. The predictive fatigue lives showed a good consistence with the experimental results of both as-received state and short-term aged Inconel 750H under various amplitudes. In addition, the validity of the proposed model was further confirmed by fatigue crack length under the initiation and propagation stages, accompanying by the 3D X-ray computed tomography.