Ultrastrong Medium-Entropy Single-Phase Alloys Designed via Severe Lattice Distortion

Sohn, S.S. and Kwiatkowski da Silva, A. and Ikeda, Y. and Körmann, F. and Lu, W. and Choi, W.S. and Gault, B. and Ponge, D. and Neugebauer, J. and Raabe, D.

Volume: 31 Pages:
DOI: 10.1002/adma.201807142
Published: 2019

Severe lattice distortion is a core effect in the design of multiprincipal element alloys with the aim to enhance yield strength, a key indicator in structural engineering. Yet, the yield strength values of medium- and high-entropy alloys investigated so far do not substantially exceed those of conventional alloys owing to the insufficient utilization of lattice distortion. Here it is shown that a simple VCoNi equiatomic medium-entropy alloy exhibits a near 1 GPa yield strength and good ductility, outperforming conventional solid-solution alloys. It is demonstrated that a wide fluctuation of the atomic bond distances in such alloys, i.e., severe lattice distortion, improves both yield stress and its sensitivity to grain size. In addition, the dislocation-mediated plasticity effectively enhances the strength–ductility relationship by generating nanosized dislocation substructures due to massive pinning. The results demonstrate that severe lattice distortion is a key property for identifying extra-strong materials for structural engineering applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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