Probing the atomic-scale deformation mechanism of single-crystal nanowires coated with a multi-component alloyed shell

Abstract

Metallic nanowires have attained considerable attention as applied for the building blocks in nano-electromechanical systems. Surface coating is needed for nanowires to prevent their degradation from the external environment. Multi-component alloys (MCAs) exhibit a combination of exceptional fracture tolerance and desirable corrosion resistance, which are promising coating materials for nanowires. However, few attempts have been made to investigate the deformation mechanisms of nanowires coated with an MCA shell. To address this gap, we employ atomic simulations on investigating the tensile deformation of single-crystal nickel nanowires coated with MCA shells, and study the microstructural features governing the necking behavior of these specimens. The results indicate that the dislocation nucleation method controlling the incipient plasticity of the nanowire turns from a typical homogeneous surface nucleation mode to another interface nucleation one after coating, lowering the maximum stress during the tensile loading. Ductile necking with dispersed plastic events prevails in the uncoated nanowire, while severely localized shear dominates the necking mode of the single- and poly-crystalline MCA nanowire due to their lower dislocation contents as well as the sluggish dislocation mobility caused by lattice distortion and high-entropy effect. The necking mode of nanowires is not altered by the MCA coating due to the predominant volume fraction of the nickel core in the present configurations. Noteworthily, the deformation stability is highly enhanced by polycrystalline MCA coating, thus the stress no longer drops to zero before the final fracture. This work gives new insights into developing reliable nanowires with enhanced deformability via using MCA coating.