Simulation of tensile deformation of twin silver nanowires based on molecular dynamics

Abstract

This study investigated the deformation behavior of <111> twin Ag nanowires with differing parallel twin boundary (TB) densities under tensile loading via molecular dynamics (MD) simulations. The effect of TB density on the ultimate stress of nanowires is discussed, and the plastic deformation mechanisms of nanowires are illustrated. The results show that, in contrast to a single crystalline nanowire with the same size, the introduction of the TB can strengthen or soften nanowires through individual deformation modes, which indicates that there exists a critical twin boundary space (TBS) (where the value of the critical 1/TBS is 0.2 nm–1). Below 0.2 nm–1, softening occurs, whereby TBs become the source of dislocations. Above 0.2 nm–1, TBs impede dislocation movement, which results in a strengthening effect. The strengthening mechanisms are divided into two types. When 1/TBS ranges from 0.2 to 0.5 nm–1, the TB-dislocation interaction is the controlling factor. Fracture opening appears within the nanowires, and voids form, with dislocation multiplication, and then spread to the surrounding regions. When 1/TBS is greater than 0.5 nm–1, TBs migrate to accommodate dislocation activity. Dislocations increase and transfer across the TBs. Shear banding is activated during the process, which contributes to the necking of nanowires. The strengthening and weakening effects caused by differences in TB density decrease with increasing temperature.