Analogous mechanical behaviors in (100) and (110) directions of Cu nanowires under tension and compression at a high strain rate

摘要

This study analyzes the plastic deformation on the atomic scale of Cu nanowires ( NWs) with [100] and [110] orientations during uniaxial tension and compression, using a molecular dynamic simulation. The maximum local stress ( MLS) method is employed to evaluate mechanical behavior during deformation. Following yielding, the flow stress strongly depends on the variation in the degree of orientation caused by twinning. Both the tension of the [100] NW and the compression of the [110] NW cause twin deformation and consequent geometrical softening. In contrast, the compression of the [100] NW and the tension of the [110] NW form twin bands and cause geometrical hardening. These behaviors result in the stress-strain curves that reveal the pseudo-skew-symmetry characteristic. With respect to the difference between the critical resolved shear stress (tau(c)) associated with the distinct orientations, tc depends strongly on the surface critical resolved stress (tau(sc)). Under tension, tsc depends on the degree of lattice distortion. A larger lattice distortion ( pre- tensile stress) corresponds to higher tsc. However, under compression, a geometrical factor can be used to describe the difference in tsc between the different orientations. A larger geometrical factor corresponds to a larger tsc.