Tungsten content and grain boundary misorientation angle effect on crack blunting in nanocrystalline Ni-W alloy

The effect of tungsten (W) content and grain boundary misorientation angle (GBMOA) on crack blunting of nanocrystalline Ni-W alloy (20-100 nm) is researched theoretically, considering the coupled effects of dislocations and grain boundaries (GBs). In our proposed model, W atoms are clustered in the dislocation free region (DFZ), impeding dislocation slip, and W additions lead to GB segregation so that the boundary energy is reduced. The dislocations emitted from the crack tip are stopped at or/and penetrated through GBs, which depends on the total force acting on the dislocations as well as the critical penetration stress. The critical penetration stress is bound up with GB energy and residual Burgers vector. The number of dislocations emitted from the crack tip and penetrated through GB is calculated by using W content and GBMOA. The results show that an increase in W content decreases the critical penetration stress and increases the number of dislocations emitted from the crack tip. The critical stress intensity factors by considering the interactions between dislocations and GBs are larger than those of dislocations stayed at GBs. It is demonstrated that crack blunting depends significantly on both W content and GBMOA.