Atomic Simulations On Mechanical Behavior And Deformation Mechanism Of Cu/CuZr Nanocomposites

Nano-polycrystal metal materials have received extensive attention in various fields in recent years due to their excellent mechanical properties such as high plasticity and high strength.The research on the mechanical properties and deformation mechanism of nano-polycrystal metal materials mainly focuses on the face-centered cubic(fcc)structure,especially the mechanical properties of nano-polycrystal Cu.When studying the deformation mechanism of nano-polycrystal Cu under tensile load,it was found that nanopores or cracks appeared at the grain boundary due to stress concentration,which led to the decrease of plasticity of nano-polycrystal Cu.Therefore,it is necessary to find a suitable method to improve the plasticity of nano-polycrystal Cu.Amorphous alloys have good wear resistance and corrosion resistance.When the size of amorphous alloys is reduced to a certain critical value,it exhibits good uniform plastic deformation during deformation and shows good plasticity.It has been found that the crystalline phase introduced into an amorphous alloy can effectively improve the plasticity of an amorphous alloy by increasing the nucleation point of the shear band or hindering the movement of the shear band.In order to find a way to improve the mechanical properties of nano-polycrystal Cu,the mechanical properties of dual-phase nanostructured copper alloys are a concern.In this paper,the influence of CuZr amorphous on nano-polycrystal Cu under tensile load is studied by molecular dynamics simulation.The main contents and conclusions are as follows:(1)The effects of grain size on the plastic deformation mechanism of nano-polycrystal Cu and dual-phase nanostructured Cu/CuZr composites under tensile loading was investigated.The results show that the deformation mechanism of nano-polycrystal Cu with small grain size is mainly dominated by grain rotation and grain boundary migration,accompanied by nucleation and slip of a few dislocations.The plastic deformation mechanism of nano-polycrystal Cu with large grain size is mainly based on the nucleation and growth of cracks.For the dual-phase nanostructured Cu/CuZr composite,the plastic deformation of the amorphous phase plays a leading role in the plastic deformation process,and this phenomenon is independent of the grain size.In addition,when the grain size increases to a certain size,grain boundary cracks appear at the grain boundary of the composite,but the amorphous phase significantly retards and hinders the nucleation and expansion of the crack.Studies have shown that the introduction of amorphous phase can effectively improve the plasticity of nano-polycrystal Cu.The effect of temperature on the plastic deformation mechanism of dual-phase nanostructured CuZr composites was also studied.The results show that the effect of temperature on the plastic deformation mechanism of dual-phase nanostructured Cu/CuZr composites is mainly dislocation.When the temperature rises,the dislocations of material is more susceptible to nucleation and slippage during tensile process.(2)The effect of amorphous phase on the plastic deformation behavior of nano-polycrystal Cu was investigated.The effect of amorphous boundary(AB)spacing and grain size on the deformation mechanism of crystalline/amorphous Cu/CuZr nanocomposites was studied in detail.The results show that the introduction of amorphous phase can effectively enhance the plasticity of nano-polycrystal Cu owing to the cooperation interactions between amorphous and crystalline phases.With the grain size decreased or AB spacing increased,the deformation mechanism in crystalline grains of nanocomposites transforms from the dislocations slipping of double slip systems to the dislocations slipping of a single slip system,and the amorphous phase bears the plastic deformation of the entire sample is gradually improved.That is to say,reducing grain size and increasing AB spacing can improve the plastic deformation ability of the Cu/CuZr nanocomposites.Although the nucleation and slipping of dislocations occur during the plastic deformation of Cu/CuZr nanocomposites,the cooperation interactions between amorphous phase and crystalline phases plays a dominant role,especially in the later stage of plastic deformation.This study has reference and guiding significance for improving the plasticity of nano-polycrystal Cu.