Molecular Dynamics Study On Microscopic Defecte Volution Mechanism Of Severe Plastic Deformation Of Copper

In recent years,with the development of science and technology,people's requirements for the performance of materials have become higher and higher.Nano-metal materials have been widely used in more and more fields because of the special mechanical properties of nano-crystalline materials,such as nano-scale grain size,higher hardness,strength and ductility.Its properties are far better than ordinary materials.In order to improve the properties of the metal by changing the microstructure of the material,we need to understand the impacts of microscopic defects on the properties of metal materials.Therefore,it is of great significance to understand the mechanical properties of nano-metal materials and to design materials that meet people's needs.In this paper,starting from the microscopic scale,the simulation method of molecular dynamics is used to simulate the severe plastic deformation process of the single crystal Cu,and the microstructure evolution mechanism of the dislocation in the plastic deformation process is studied.Visual analysis software is used to visualize the micro structural simulation process of the material in different stages.This paper studied that the evolution of dislocation structure in the deformation mechanism of nanoscale cubic metal,such as dislocation proliferation,dislocation plug,grain boundary movement and so on,to explore its influence on the macro performance.Finally,it is compared with the simulation results of single crystal Ni.The results show that during the plastic deformation process,the dislocation is mainly caused by the proliferation of Frank-Read source.The single crystal Cu and Ni in the drawing stage,the sliding surface and the sliding direction tend to the direction of the tensile axis,in the compression stage,the sliding surface is gradually perpendicular to the direction of the pressure axis.At the same time,a comparison of copper and nickel dislocation densities shows that the more grain boundaries present in the material,the greater the dislocation density.With the analysis of the relation between the stress and the density,it is concluded that the dislocations are bound to move,proliferate and disappear within the material when the material appears plastic deformation,and the movement of these dislocations eventually achieves the purpose of grain refinement.