Effects of twin orientation and spacing on the mechanical properties of Cu nanowires

Abstract

The role of twin orientation in mechanical behaviors of nanomaterials is drawing increasing attention. In this paper, atomistic simulations on the tensile deformation of twinned Cu nanowires (NWs) are implemented to investigate the twin orientation and spacing effects. The results of numerical simulations reveal that the tensile deformation mechanisms can be divided into three types with the twin orientation varying from 0° to 90°: dislocations slip intersecting with twin boundary (TB), stacking faults formed parallel to the TB and TB migration. Detail analysis about dislocation motion is carried out to illustrate the plastic deformation mechanisms. In addition, with the increasing of the TB spacing, there is a transition from yield with strain hardening to yield with nearly constant flow stress. The peak stress decreases with the increase of TB spacing, which can be attributed to surface roughness caused by crystal reorientation. Our findings also suggest a possible approach to tune the mechanical behaviors of low dimensional nanostructures.

Rebuilding the Strain Hardening at a Large Strain in Twinned Au Nanowires

“…The similar strain hardening behavior has been observed in the NT Cu nanowires with square cross section and slant CTBs [ 29 ], when the oriented angle is 19.47°, 35.26°, and 54.74°. In contrast, the unique strain hardening behavior occurs only as the oriented angle is 54.74° in the NT Au nanowires.…”

“…The slant CTBs are subjected to nonzero resolved shear stresses during axial tension/compression of nanowires. Thus, twin migration or detwinning is a governing deformation mechanism, and thus facilitates a large amount of plasticity [ 13 , 28 , 29 ]. Experiments and MD simulations all proved that the mechanical behavior and deformation mechanism were significantly related to the twin orientation respective to the load direction.…”

“…Three slip modes and different interactions of dislocations were observed in deformation at 0°, 45°, and 90° with respect to CTBs. The detailed dislocation process and mechanical behavior of NT Cu nanowires were examined by recent MD simulations [ 29 , 31 , 32 ]. The results demonstrated that the dominant deformation mechanism of NT Cu nanowires transits dynamically from slip transmission to twin boundary migration to slip-twin interactions as the twin boundary orientation changes from horizontal to slant, and then to a vertical direction.…”

Role of axial twin boundaries on deformation mechanisms in Cu nanopillars

“…In nanopillars with smaller twin boundary spacing, the high repulsive force makes the dislocation nucleation and glide difficult, thus giving rise to increase in yield strength. Figure 12b compares the yield stress values of twinned nanopillars in the present study with that reported in other studies in literature [9,12,14,15]. Similar to the present study, many studies in the literature have reported that the yield stress decreases with increasing twin boundary spacing.…”

“…It can be seen that the yield stress of all the twinned nanopillars falls above the horizontal line ( Figure 3), indicating that the strength of twinned nanopillars is higher the perfect twin free nanopillars. Further, the yield stress values under tensile and compressive loading decreases with increasing twin (Figure 3), which is similar to that observed in orthogonally twinned FCC nanopillars [1,7,12,14,16]. It can also be seen that, for perfect as well as twinned nanopillars, the yield stress values under tensile loading are higher than that in compressive loading i.e., all the nanopillars display tension-compression asymmetry in yield stress.…”