Molecular Dynamics Simulation Of Fatigue Behavior Of Single Crystal Zirconium Under Cyclic Loading

Zirconium as a transition metal can absorb oxygen,nitrogen and other elements,used for instrument cleaning;Zirconium also can be added to steel or iron as an additive element to enhance the toughness of materials;At the same time,zirconium alloy is usually the main material for nuclear fuel cladding,which is the safety barrier of nuclear power plants,therefore,zirconium materials are inevitably affected by small continuous loads in actual working conditions.In this paper,the molecular dynamics(MD)method is used to simulate the crack models under cyclic loading in three different directions at room temperature,the change of the microstructure and deformation mechanism of [ 10(?)0 ](0001),[ 0001]((?)2(?)0)and[ (?)2(?)0 ](10(?)0)crack models are studied under cyclic tensile loading.The main deformation mechanisms of the [10(?)0](0001)model near the crack tip are twinning and slip,the crack expands along the twin plane;Under fatigue loading the deformation mechanism of the [ 0001]((?)2(?)0)model near the crack tip is mainly dislocation emission,and the whole model has good plasticity;However,the deformation mechanisms of [ (?)2(?)0 ](10(?)0)crack model under loading are sliding,blunting and void nucleation,in which blunting and void nucleation lead to rapid crack expansion,and crack penetrates the model and leads to model fracture.The shear stress of the corresponding slip surface is different depending on the loading directions,which indicates the influence of the crystal orientation on the microcosmic mechanism of crack propagation.At the same time,the stress and crack growth rate of the model during the loading process are calculated,the influence of loading orientation on the crack propagation of the model is further analyzed;In addition,the evolution process of the internal microstructure and crack propagation of [ 0001]((?)2(?)0)and [ (?)2(?)0 ](10(?)0)models at 5K,600 K and 900 K under fatigue tensile loading were simulated respectively.At the same time,their crack growth rates are also calculated to analyze the effect of the temperature on the fatigue loading of single crystal zirconium;In order to study the effect of the loading mode on the single crystal zirconium,the fatigue compression loading is also carried out,and the deformation mechanism of the model is compared with that of the model during tension and compression.It's found that temperature and loading mode are important factors affecting fatigue behavior of single crystal zirconium.