剪切应力作用下位错运动的晶体相场模拟

Phase-field-crystal Simulation of Dislocation Gliding under Shear Strain

关键词:  位错滑移  剪切应变  模拟  晶体相场模型

Key words:  dislocation glide  shear strain  simulation  phase field crystal model

摘要:

[目的]研究剪切应变作用下晶体的位错攀滑移运动特征,揭示原子晶格势垒、剪切应变对位错运动特征的作用机理。[方法]根据位错滑移运动,构建包含外力场与晶格原子密度耦合作用项的体系自由能密度函数,建立剪切应变作用体系的晶体相场模型,模拟位错攀移和滑移运动,计算临界应变。[结果]位错攀移克服的势垒大于滑移的阻力势垒;位错启动运动,存在临界的势垒;施加较大的剪切应变率作用,体系能量变化为单调光滑曲线,位错以恒定速度作连续运动,具有刚性运动特征;剪切应变率较小时,体系能量变化出现周期波动特征,位错运动是处于低速不连续运动状态。[结论]位错攀移和滑移运动特征与实验结果相符合。

Abstract:

[Objective] The feature and machanism of dislocation gliding and climbing movement were studied under shear strain.[Methods] The free energy density functional is constructed including the exerting shear force and atomic density term, and also the phase field crystal model is established for the system of shear stain.The process of glide and climb is simulated and critical shear strain is calculated.[Results] Dislocation climbing to overcome the barrier is greater than the slip resistance barrier.There is a critical barrier for activating dislocation movement.The results show that the energy curves changing with time are monotonous smooth under greater shear strain rate, and of rigorous character corresponding to dislocation movement, and move with a constant speed;while under less shear strain rate, the energy change curves of system present a periodic wave feature.There is a critical potential for dislocation starting movement.[Conclusion] The results in these simulations are in a good agreement with the experimental ones.