纳米单晶与多晶铜薄膜力学行为的数值模拟研究

通过对不同温度下单晶薄膜的拉伸性能的分子动力学模拟，从微观角度揭示了温度效应对材料性能的影响. 结果表明温度效应对材料的变形机理影响很大.0K温度下由于缺乏热激活软化的影响, 粒子运动所受到的阻碍较大, 薄膜的强度较高, 塑性变形主要来自于粒子的短程滑移.温度升高，粒子的热运动加剧，屈服强度降低, 塑性变形将主要来自于大范围的位错长程扩展.多晶薄膜的模拟结果表明, 虽然其晶粒形状较为特殊, 但是它仍然遵循反Hall-Petch关系.在模拟过程中，侧向应力最大值比拉伸方向应力的最大值滞后出现.位错只会从晶界产生并向晶粒内部传播，晶粒间界滑移是多晶薄膜塑性变形的主要来源. 关键词： 纳米薄膜 变形机理 温度效应 分子动力学

Numerical simulation and analysis on the mechanical behaviors of the single-crystalline and poly-crystalline nano-Cu film

Molecular dynamics simulation and analysis are performed on the mechanical properties of mono_and poly_crystalline nano-Cu film. Computational results indicate that the temperature effects are very significant on the tensile strength and the deformation mechanism of the mono-crystalline Cu-film. The strength of the sample is much higher at absolute zero temperature than at normal temperature. The plastic deformation at zero temperature is induced by the short-distantce sliding of the particles while it is caused by the long-distance propagation of dislocations at normal temperature. The strength of polycrystalline Cu-film increases with the decrease of grain size. In the process of strain accretion, grain boundary sliding dominates the plastic deformation. Dislocations originating from grain boundaries propagate toward grains. The area of the grain boundary enlarges and the grain size shrinks with the development of plastic deformation. However, the shapes of the basic grains have no remarkable change even at very large strain.