Sub-Micron Scale Crystal Plastic Deformation Study By Discrete Dislocation Dynamics

In recent years,micro-electromechanical systems（MEMS）have been widely used in the fields of microelectronics,communication,medicine,and advanced manufacturing.In this case,the dimensions and grain sizes of the components are under the same magnitude.The mechanical properties of the material exhibit strong dimensional effects and spatiotemporal discontinuities.Dislocation is the basic carrier for plastic deformation of crystal materials,so it is necessary to analyze the mechanism of dislocation evolution during plastic deformation of materials at submicron scale.In order to study the mechanical properties and the evolution of dislocations in submicron materials under these conditions,the following research was applied to the application of discrete dislocation dynamics.Based on the analysis of the interaction between dislocation and grain boundary,this paper proposes a dislocation-grain boundary interaction model,and then implants the model into the discrete dislocation dynamics software ParaDis,which is the three-dimensional discrete dislocation dynamic of submicron polycrystalline materials.The simulation provides an effective computational tool and is of positive significance for further understanding of the intrinsic mechanism of plastic deformation of polycrystalline materials.During the research,it was found that the initial dislocation density in the crystal and the strain rate experienced during the deformation have a great influence on the mechanical properties of the material.The strength of the material decreases first and then increases with the increase of the initial dislocation density under the constant strain rate.The critical initial dislocation density is 10¹²m^-2.When the dislocation density is low,the strength of the material increases with the increase of the strain rate.When the initial dislocation density is high,the strength of the material does not change substantially with the increase of the strain rate,and the plastic deformation of the material is mainly It is a single slip mechanism.By introducing the interaction model between dislocations and grain boundaries into the three-dimensional discrete dislocation dynamics,it is found that there is a critical orientation,θ_mis,and when it is larger than this angle,the dislocations are more likely to slip along the grain boundary.Below this angle,the dislocations tend to penetrate the grain boundaries.When the angle is higher than the critical value,the intensity is slowly increased as the orientation increases,and the strength of the material rapidly increases as the difference in orientation between the crystals grains increases from zero.And the critical angle is approximately equal to 15°.