The Simulation Research Of Tensile Mechanical Properties And Deformation Mechanism Of Ni-Co Alloys

Due to its excellent properties,Ni-Co alloy has shown great potential in the fields of mems and aerospace.There have been a lot of researches on the macroscopic system of Ni-Co alloy.The macroscopic system is essentially composed of a large number of microstructure,so the behavior and mechanism of the microscopic system under deformation are still worth studying.In this paper,the molecular d ynamics method is used to study the micromechanical behavior and deformation mechanism of Ni-Co alloy at the nanoscale to provide theoretical basis and guidance for the practical application of the alloy nanostructure.(1)The yield strength and young's modulus of Ni-Co single crystal alloy nano pillars showed a linear growth trend when the content of Co in the alloy increased from 0 to 20% during tensile loading.In the deformation process of alloy nano pillars with Co content of 10%,the number of stair-rod dislocations formed by dislocations increases,and a set of 5 stacking fault tetrahedrons is formed.This structure can absorb and fix the dislocations,effectively improve the stress in the plastic deformation stage,that is,strain hardening phenomenon,and thus strengthen the nano pillars.[100],[110],[111] crystals have different number of movable slip systems leading to different deformation patterns,among which [110] crystals have a single dislocation generated in the upward direction and the for mation of twins has no effect on the strength of the nano pillars.In the 50 K temperature deformation,the full reaction between the dislocations promoted the generation of prismatic dislocation ring.The strength of the nano pillars was enhanced due to the fixation effect of the modified structure on the dislocation.The increase of strain rate during loading can promote the rapid reaction proliferation of dislocations and lead to the increase of dislocation density.The influence of intracrystalline cavity o n the performance of nano pillars includes that the existence of a small internal cavity can promote dislocation nucleation and increase dislocation density.The plastic deformation process is close to fracture failure due to the existence of large void.(2)Compared with single crystal nano pillars,the introduction of twin boundary has a great influence on the deformation mode of nano pillars.When the twin boundary is less than two layers,the existence of the twin boundary weakens the strength of the nano pillars.When the twin boundary contained in the nano pillars exceeds two layers,the twin boundary hinders the dislocation obviously.The migration of the twin boundary and the reaction between the dislocation and the twin boundary lead to the increase of the dislocation contained in the nano pillars.The existence of the multi-layer twin boundary strengthens the strength of the nano pillars.When the temperature increases,the reaction between dislocation and twin boundary will eliminate part of twin boundary.With the increase of strain rate,the main deformation mode of nano pillars changed from dislocation to twin boundary to twin boundary migration.When the nano pillars containing a layer of twin boundary is deformed,the increase of the void volume ratio at the grain boundary leads to the obvious reduction of the yield strength and young's modulus of the nano pillars.When the void volume ratio at the grain boundary is greater than 2.3%,the stress fluctuation in the plastic deformation stage of the nano pillars is similar to the fracture process.Where the hollow twin boundary meets the surface of the nano pillars is the most severely deformed part of the nano pillars.