纳米铜双晶拉伸与剪切变形的分子动力学模拟

Molecular Dynamics Simulation of Uniaxial Tensile Deformation and Shear Deformation for Nano-Bicrystal Copper

用分子动力学方法模拟了纳尺度铜双晶 ( 1 1 1 )面原子层的拉伸与剪切变形。模拟结果显示纳米铜双晶的拉伸与剪切变形都是由弹性变形与塑性变形两个阶段构成。在弹性变形阶段原子排列结构不变 ,而塑性变形阶段此排列结构发生较大变化 ,包括金属键断裂 ,原子与空位迁移、重组 ,晶界变形、迁移等。这种微观变形机制直接决定了相应的应力应变关系 :在弹性变形阶段 ,虎克定律依然成立 ;在塑性变形阶段 ,应力应变曲线产生很大波动 ,其波动情况与微观变形密切相关。模拟还发现纳米铜晶体的塑性比宏观材料好得多 。

The uniaxial tensile deformation and shear deformation of nano bicrystal copper within (111) atomic layer are studied with molecular dynamics. Simulation shows that both tensile and shear deformation consists of a elastic and a plastic periods. When deformation is elastic the initial configuration of atomic system changes little, obvious change is observed in plastic period, such as break of metal bond,movement of atoms and pores,migration of grain boundary. The deformation mechanism directly determines the corresponding stress strain curve:the curve is linear in elastic period which coincides with the Huke Law; the curve fluctuates greatly in plastic period according to the microscopic deformation mechanism. It is also found that the two copper grains can be linked by just one atom at the end of plastic period, which manifests the excellent plasticity of nanocrystalline copper.