界面缺陷密度对铜纳米线力学性能影响的模拟研究

Effect of Density of Interfacial Defect on Mechanical Properties of Copper Nanowires

本文通过分子动力学模拟方法,研究了孪晶和堆垛层错的界面缺陷对铜纳米线力学性能的影响。研究结果表明:当孪晶界面存在缺陷时,界面缺陷会显著降低铜纳米线的屈服强度。界面缺陷密度的改变对铜纳米线的屈服强度影响很小,但却可以影响位错成核的位置:界面缺陷较少时,位错成核于缺陷界面相邻的完整孪晶面,界面缺陷数量增加后,若缺陷与自由表面之间形成内禀层错,则位错首先成核于内禀层错与自由表面交界处;然而,当堆垛层错界面存在界面缺陷时,铜纳米线的屈服强度由于应力过早集中而明显降低,位错成核于含有缺陷的堆垛层错界面与自由表面的交界处。界面缺陷密度较大时,缺陷界面会形成外禀层错。包含有堆垛层错的铜纳米线的屈服强度随着界面缺陷密度的增大而减小。

The effect of interfacial defect on mechanical properties of copper nanowires (NWs) containing twin boundaries (TBs) and stacking faults (SFs) is investigated using the molecular dynamics simulation. The results indicate that when the TB is coupled with interfacial defects, the strength of NWs is reduced. The density of interfacial defects influences the nucleation location regardless of the yield strength. The dislocation will emit at the adjacent perfect twin boundary or the intrinsic SF induced by the defect depending on the density of interfacial defects. However, when the interfacial defects are in the SF, the dislocation induced by the interfacial defect will slip along the SF or in the SF and eventually pile up at the junction of SF and free surface. As the emergence of stress concentration, the yield strength is also reduced. The yield strength of NWs containing SF will obviously decrease as the increase of number density of interfacial defects.