The fatigue crack propagation in nanocrystalline materials in the hydrogen environment

•Based on the discrete dislocation method, the corrosion fatigue crack propagation model in nanocrystal materials is established.•When the distance between the hydrogen atom group and the crack tip is 2 nm, the crack growth rate in the hydrogen environment is increased by about 45% compared with the air environment.•The grain size can affect the roughness of the material surface, leading to a significant impact on the FCP rate. The larger the grain size, the rougher the material surface, leading to an accelerated crack propagation rate.•The change in the distance xh between hydrogen clusters and crack tips has a smaller impact on fatigue crack propagation than the change in hydrogen cluster radius rh. In this article, the effect of the external corrosion environment on dislocation emission is introduced, and the microscopic mechanism of fatigue crack propagation (FCP) in a hydrogen environment is studied. Meanwhile, based on the discrete distributed dislocation method, the corrosion FCP model of nanocrystal materials is established. In the framework of our model, the FCP is mainly determined by the irreversibility of the crack tip dislocation. The research results indicate that the aggregation of hydrogen atoms at the crack tip (CT) promotes the dislocations emission and increases the FCP rate. Meanwhile, considering the application of materials in different hydrogen circumstances, the effects of changes in the distance between hydrogen atoms and the crack tip and the radius of hydrogen atoms on crack propagation rate are studied. The results show that the accumulation of hydrogen atoms at the crack tip promotes the fatigue crack growth rate in nanocrystalline materials. Compared with the air environment, the maximum increase in crack propagation rate is about 45% under the action of hydrogen environment. Meanwhile, increasing the grain size and dislocation emission angle helps to increase the crack propagation rate. The research in this paper provides a theoretical basis for evaluating the corrosion fatigue life of metal materials.