Transformation from slip to plastic flow deformation mechanism during tensile deformation of zirconium nanocontacts

Kohei Yamada,Tokushi Kizuka

doi:10.1038/srep42901

Abstract

Various types of nanometer-sized structures have been applied to advanced functional and structural devices. Inherent structures, thermal stability, and properties of such nanostructures are emphasized when their size is decreased to several nanometers, especially, to several atoms. In this study, we observed the atomistic tensile deformation process of zirconium nanocontacts, which are typical nanostructures used in connection of nanometer-sized wires, transistors, and diodes, memory devices, and sensors, by in situ transmission electron microscopy. It was found that the contact was deformed via a plastic flow mechanism, which differs from the slip on lattice planes frequently observed in metals, and that the crystallinity became disordered. The various irregular relaxed structures formed during the deformation process affected the conductance.

Highlights

Various types of nanometer-sized structures have been applied to advanced functional and structural devices
As the width of deformation region is reduced to several atoms, the deformation mechanism is transformed from dislocation-mediated slip to non-slip manners, i.e., homogeneous slip[8,9,10,11,12]
The primary slip system of metals with hexagonal-closed packed structure is limited to only three equivalent systems on basal planes[13]

Summary

Introduction

Various types of nanometer-sized structures have been applied to advanced functional and structural devices. After the transformation of deformation mechanics, the critical shear stress of nanometer-size metals increases by several tens of times or more in comparison with that of dislocation-mediated slip, e.g., ~1 GPa for silver[11] (Ag) and ~5 GPa for rhodium[12] (Rh) Such a transformation is observed in metallic nanocontacts (NCs) with face-centered cubic (fcc) structures[10,11,12]. Atomic-size contacts of zinc (Zn) with an hcp structure show unstable melting-like behavior, related to different break conductance features from NCs of other metals[14] Theoretical treatments, such as molecular dynamics (MD) simulations, show that the atomic configuration of the deformation region becomes disordered during the deformation in NCs with width less than several atoms; the deformation proceeds while the crystal structure crumbles and all atoms in the deformation region move simultaneously in a way like atomic motion in liquid[9,15,16,17,18,19,20,21,22,23,24,25,26]. We focus on zirconium (Zr) NCs with this goal in mind

Methods

Results

Discussion

Conclusion