Discrete Dislocation Dynamics Simulation For Mechanical Behavior Of Particle Reinforced Composites

Particle reinforced metal matrix composites have high strength and ductility,excellent electrical,thermal conductivity and wear resistance,they are widely used in aerospace,rail transit,equipment manufacturing and other fields.In particle reinforced composites,the dislocation movement is prevented by small dispersed particles in the alloy,thus effectively improving the mechanical properties of metallic materials and enhancing their service safety.It is of great significance to study the mechanical behavior and structural properties of particle reinforced materials.Therefore,for particle reinforced copper matrix materials,the following studies were carried out in this paper:(1)In this paper,the three-dimensional discrete dislocation dynamics(3D-DDD)method was used to simulate the compression of particles reinforced copper matrix composites micropillar.The influence of the dislocation-precipitate interaction on the mechanical response of the material was analyzed to reveal the microscopic mechanism of the precipitation strengthening.In this study,the precipitate was regarded as a spherical particle with an impenetrable surface.The dislocation bypass mechanism was used to simulate the interaction between the precipitates and the dislocations.By changing the relative distance of dislocation slip plane against the center of spherical particle,it is found that when the distance is zero,the yield strength and the subsequent strain hardening rate are the highest.As the slip plane is far away from the center of spherical particle,the yield strength and the strain hardening rate decreases.The study also found that the higher the Schmid factor,the lower the yield strength and the lower strain hardening rate.In the simulation of multiple dislocations,it was found that the reaction of dislocations in same slip planes and the interaction of dislocations in different slip systems may be responsible for the reduction of the yield strength and the strain hardening rate.(2)The effects of particle state(particle volume fraction,particle distribution,particle shape)on microstructure and mechanical response of particle array distributed materials were further studied.It is found that the higher the particle volume fraction,the higher the yield strength and strain hardening rate.The yield strength of the homogeneous particle distribution model is higher,and it is easier to produce the interface dislocation net and stable dislocation entanglement structure in the material compared with the spherical particle tetragonal.Based on the BKS model and Orowan mechanism,the effects of the interaction between the dislocations and the precipitate on the mechanical response of the materials were analyzed,and the microscopic mechanism of the strengthening of the precipitate was revealed.(3)The interaction process between the dislocations and the precipitates was studied by compression-unload-tension simulation of particle reinforced copper matrix composite.The origin of Bauschinger effect were studied.The influence of particle reinforced structure on the back stress and effective stress was analyzed.It is found that the structure of dislocation storage,such as dislocation loop and dislocation entanglement,is the cause of Bauschinger effect,and the influence of particle reinforced structure on back stress and effective stress is analyzed.