Plasticity through De-Twinning in Twinned BCC Nanowires

G. Sainath,A. Nagesha,Sunil Goyal

doi:10.3390/cryst10050366

G. Sainath, A. Nagesha + Show 1 more

Open Access

https://doi.org/10.3390/cryst10050366

Copy DOI

Abstract

The deformation behaviour of twinned FCC nanowires has been extensively investigated in recent years. However, the same is not true for their BCC counterparts. Very few studies exist concerning the deformation behaviour of twinned BCC nanowires. In view of this, molecular dynamics (MD) simulations have been performed to understand the deformation mechanisms in twinned BCC Fe nanowires. The twin boundaries (TBs) were oriented parallel to the loading direction [110] and the number of TBs is varied from one to three. MD simulation results indicate that deformation under the compressive loading of twinned BCC Fe nanowires is dominated by a unique de-twinning mechanism involving the migration of a special twin–twin junction. This de-twinning mechanism results in the complete annihilation of pre-existing TBs along with reorientation of the nanowire. Further, it has been observed that the annihilation of pre-existing TBs has occurred through two different mechanisms, one without any resolved shear stress and other with finite and small resolved shear stress. The present study enhances our understanding of de-twinning in BCC nanowires.

Highlights

In recent years, twinned nanowires have attracted considerable attention for research due to their superior physical properties as compared to their perfect counterparts
The results show an intersecting de-twinning mechanism involving the migration of twin–twin junction, which results in a complete annihilation of pre-existing twin boundaries (TBs) and leads to the reorientation of the nanowire
Molecular dynamics simulations performed on the compressive loading of axially twinned [110]

Summary

Introduction

In recent years, twinned nanowires have attracted considerable attention for research due to their superior physical properties as compared to their perfect counterparts. Unlike the nanowires with slanted TBs, the de-twinning in nanopillar containing axial TBs is surprising due to zero resolved shear stress on the pre-existing twin boundary. Using experiments and atomistic simulations, Cheng et al [12] have reported a de-twinning mechanism in nanopillars with axial twin boundary placed closed to the surface. This de-twinning resulted in a complete annihilation of the existing twin boundary, giving rise to defect-free nanopillar. There are only a couple of investigations in the literature on BCC nanowires containing twin boundaries [14,15] These studies on BCC nanowires with transverse TBs have shown a strong tension-compression asymmetry in deformation mechanisms. The results show an intersecting de-twinning mechanism involving the migration of twin–twin junction, which results in a complete annihilation of pre-existing TBs and leads to the reorientation of the nanowire

MD Simulation Details

Results And Discussion

Conclusions