单晶铜纳米线弯曲、扭转的变形机制的分子动力学研究

本文利用分子动力学方法研究了〈001〉/{100}和〈110〉/{111}两种单晶铜纳米线在弯曲、扭转载荷作用下的变形机制和力学行为.在〈001〉/{100}铜纳米线的弯曲过程中,当弯曲角度很大时,我们观察到了一些五重变形孪晶.分析表明,配位数为12的其它原子类型与hcp原子类型间的相互转化是导致出现这种五重变形孪晶的重要因素.这个结果与文献（Appl Phys Lett,2006,89：041919）所报道的纳米晶铜在拉伸状态下所观察到的五重变形孪晶的形成过程截然不同;然而该孪生变形机制并未在相应的？110？/{111}单晶铜纳米线的弯曲加载过程中被发现.此外,通过对〈001〉/{100}和？110？/{111}单晶铜纳米线进行扭转模拟,我们发现,这两种纳米线的扭转塑性变形分别是以从表面边角和侧表面发射全位错为主的变形机制.

Atomistic simulations on the mechanical behavior of singlecrystalline Cu nanowires under bending and torsion loads

Molecular dynamics simulations are used to investigate the mechanical behaviors of 〈001 〉/{ 100 } and 〈 110〉/{ 111 } single-crystalline Cu nanowires under bending and torsion. In the numerical simulations of 〈001〉/{100} Cu nanowires subjected to bending, some fivefold deformation twins are observed at large bending angles. It is found that a reciprocal phase transformation from atoms of other 12-coordinate lattice to hcp lattice plays an important role in forming the fivefold deformation twins. Therefore, the formation process is distinct from that reported by Cao and Wei Appl. Phys. Lett. 89, 041919 （2006）] in nanocrystalline Cu systems. However, for the 〈110〉/{ 111 } counterparts under bending, fivefold deformation twin can not be observed during the whole deformation process. In addition, we reveal that the emission of full dislocations from the two ends of the wire is the major deformation mechanism for 〈001〉/{ 100} Cu nanowires to torsion, while for 〈110〉/{ 111 } Cu samples, the nucleation of full dislocations from the side surfaces is responsible for the torsion plastic deformation. s