Size-dependent deformation behavior of dual-phase, nanostructured CrCoNi medium-entropy alloy

Document Type

Journal Article

Publication Title

Science China Materials

ISSN

20958226

Publisher

Springer

School

School of Engineering

RAS ID

39651

Funders

Australian Research Council Fundamental Research Funds for the Central Universities Robinson Fellowship Scheme of the University of Sydney

Grant Number

ARC Number : DE170100053

Grant Link

http://purl.org/au-research/grants/arc/DE170100053

Comments

Chen, Y., An, X., Zhou, Z., Munroe, P., Zhang, S., Liao, X., & Xie, Z. (2021). Size-dependent deformation behavior of dual-phase, nanostructured CrCoNi medium-entropy alloy. Science China Materials, 64, 209-222. https://doi.org/10.1007/s40843-020-1377-2

Abstract

© 2020, Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature. The mechanical size effect of nanostructured, dual-phase CrCoNi medium-entropy alloy (MEA) was investigated by combining in-situ micro-compression testing with post-mortem electron microscopy analysis. The alloy possesses a superior yield strength up to ∼4 GPa, primarily due to its hierarchical microstructure including column nanograins, preferred orientation, a high density of planar defects and the presence of the hexagonal close packed (HCP) phase. While the yield strength of the alloy has shown size-independency, the deformation behaviour was strongly dependent on the sample size. Specifically, with decreasing the pillar diameters, the dominant deformation mode changed from highly localized and catastrophic shear banding to apparently homogeneous deformation with appreciable plasticity. This transition is believed to be governed by the size-dependent critical stress required for a shear band traversing the pillar and mediated by the competition between shear-induced softening and subsequent hardening mechanisms. In addition, an unexpected phase transformation from HCP to face-centered cubic (FCC) was observed in the highly localized deformation zones, leading to strain softening that contributed to accommodating plasticity. These findings provide insights into the criticality of sample dimensions in influencing mechanical behaviors of nanostructured metallic materials used for nanoelectromechanical systems.

DOI

10.1007/s40843-020-1377-2

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Link to publisher version (DOI)

10.1007/s40843-020-1377-2