Tailored tensile properties of CoCrNi medium entropy alloy by tuning the elemental distribution

JQ Zhu and LG Sun and ZW Bie and XB Tian and XQ He, JOURNAL OF ALLOYS AND COMPOUNDS, 897, 163171 (2022).

DOI: 10.1016/j.jallcom.2021.163171

High/medium entropy alloys (HEAs/MEAs), emerged as a new exciting class of materials, have inspired the exploration of the vast compositional space. Their unique multi-component feature makes the in homogeneity of the local chemical environment appear inevitably. Compared with traditional alloys, one of the decisive advantages of HEAs/MEAs is the tunability of their inhomogeneous elemental distribution, which holds promise for obtaining unexpected mechanical properties. Accordingly, issues regarding the effect of chemical inhomogeneity are gradually paid more and more attention. Here, a series of comprehensive atomistic simulations on chemically inhomogeneous face-centered cubic (fcc) CoCrNi MEAs are carried out to study the effect of compositional gradient on tensile behaviors of MEA and the corresponding atomic-scale mechanisms. The simulation results on cubic single crystalline CoCrNi MEAs revealed that the local absolute concentration of each element is the primary factor affecting the tensile properties of MEAs. Dislocation nucleation is found to occur at the Cr-rich region due to the localized shear deformation induced by chemical inhomogeneity, and thus result in a decrease of tensile strength. Subsequently, based on a series of simulations on equiatomic CoCrNi nanopillars with different compositional periodicity, we found that ingenious design of compositional periodicity can improve the tensile strength and plastic deformation ability owing to the plastic strain delocalization stemming from the compositional periodicity. Thus, optimization design of chemical inhomogeneity in HEAs/MEAs can turn the disadvantages of local performance degradation into benefits through enhancing the plastic strain delocalization, which is one of the effective means to promote the strength-plasticity synergy. (c) 2021 Elsevier B.V. All rights reserved.

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