颗粒增强复合材料压缩行为的位错动力学模拟

颗粒增强铜基复合材料因具有极高的强度和弹性模量, 优异的导电、导热性能和抗磨损能力, 被广泛应用于航天航空、汽车、电子工业等领域. 第二相强化是其主要的强化方式, 其通过合金中弥散的微粒阻碍位错运动, 可有效提高金属材料的力学性能, 提高其服役安全. 针对该问题本文采用三维离散位错动力学(three-dimensional discrete dislocation dynamics, 3D-DDD)方法, 对微尺度颗粒增强铜基复合材料进行了微柱压缩模拟, 分析了位错与第二相颗粒交互作用对材料力学响应的影响, 揭示第二相颗粒强化的微观机理. 本研究将第二相颗粒视为位错不可穿透的球形微粒, 采用位错绕过机制模拟颗粒与位错的交互作用过程. 通过调控滑移面相对于第二相颗粒中心的距离发现: 屈服应力和应变硬化率均随距离的增大而减小. 研究也发现Schmid因子越高的滑移系, 屈服应力越低, 后续应变硬化率越低. 多位错与颗粒交互作用的模拟发现, 同一滑移面中位错间的反应和不同滑移系中位错的交互作用可能是导致屈服应力和应变硬化率降低的关键. 

DISCRETE DISLOCATION DYNAMICS SIMULATIONS FOR COMPRESSION OF PARTICLE REINFORCED COMPOSITES

Particle reinforced copper matrix composites have high strength, elastic modulus, excellent electrical and 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. In this paper, the three-dimensional discrete dislocation dynamics (3D-DDD) method was used to simulate the compression of particles reinforced copper matrix composites micro-pillar. 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.