The fatigue crack propagation in nanocrystalline materials in the hydrogen environment

Abstract

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.