中文摘要：

单晶铱具有良好的物理、化学性能，应用范围广，但目前对于纳米级别的单晶铱研究较少，本文采用分子动力学方法模拟不同应变率下纳米级别单晶铱单轴拉伸性能。研究结果表明，应变率的变化对应力应变曲线的弹性变形阶段和塑性变形阶段都有影响，且对塑性变形阶段影响较大。不同应变率对应的纳米级单晶铱的变形机制不同，当应变率小于0.0003 ps^-1时，应变率的变化不会对材料的力学性能产生影响，断裂为脆性断裂；当应变率增大到0.0004 ps^-1时，变形机制由脆性断裂逐渐向低塑性断裂过渡；当应变率达到0.001 ps^-1时，变形过程中晶体沿（110）晶面发生滑移，断口附近有颈缩产生。

英文摘要：

Due to the good physical and chemical properties, single crystal Iridium has a wide range of applications. However, the existing study about the deformation behavior of nano-sized single crystal Iridium is little. In the present paper, the nano-sized single crystal Iridium under uniaxial tension and different strain rate is simulated by using the molecular dynamics. The calculated results indicate that the variation of strain rate has influence not only on the elastic stage but also on the plastic stage, and has more influence on the plastic stage. Different strain rate leads to different deformation mechanism. When the strain rate is below 0.000 3 ps-1, the variation of strain rate has no significant effect on the mechanical properties of the crystal and it exhibits brittle fracture. While the strain rate is greater than 0.000 4 ps-1, the deformation mechanism changes from brittle fracture to low plastic fracture. When the strain rate exceeds 0.001 ps-1, nano-sized single crystal Iridium slips along （110） plane, and there is some necking near the fracture.