Design of metastable complex-concentrated alloys through composition tailoring

To develop alloys with high strength and reasonable ductility, CoCrFeNi-based metastable complex -concentrated alloys were designed using composition-property contour maps. The map was constructed by exploring the phase stability and mechanical behaviors of a series of CoCrFeNi alloy thin films synthe-sized via solid-state alloying of multilayer thin films. The concentrations of Co and Ni were key to activate metastable deformation behaviors by reducing the stacking fault energy of alloys and improve solid -solution strengthening, as expected from the atomic-level complexity related to the electronegativity dif-ference. By optimizing the Co and Ni concentrations based on the composition-phase/mechanical prop-erty contour maps, we activated the combined deformation behavior of mechanical twinning and phase transformation. This resulted in a Co33Cr25Fe25Ni17 metastable complex-concentrated alloy with excel-lent tensile properties-yield strength of 234 MPa, ultimate tensile strength of 720 MPa, and elongation to failure of 80%. The proposed approach provides a useful guideline for the design of complex -concentrated alloys with customized properties through property predictive control.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).