Towards ultrastrong and ductile medium-entropy alloy through dual-phase ultrafine-grained architecture

Advanced materials with superior comprehensive mechanical properties are strongly desired, but it has long been a challenge to achieve high ductility in high-strength materials. Here, we proposed a new V0.5Cr0.5CoNi medium-entropy alloy (MEA) with a face-centered cubic/hexagonal close-packed (FCC/HCP) dual-phase ultrafine-grained (UFG) architecture containing stacking faults (SFs) and local chemical order (LCO) in HCP solid solution, to obtain an ultrahigh yield strength of 1476 MPa and uniform elongation of 13.2% at ambient temperature. The ultrahigh yield strength originates mainly from fine grain strengthening of the UFG FCC matrix and HCP second-phase strengthening assisted by the SFs and LCO inside, whereas the large ductility correlates to the superior ability of the UFG FCC matrix to storage dislocations and the function of deformation-induced SFs in the vicinity of the FCC/HCP boundary to eliminate the stress concentration. This work provides new guidance by engineering novel composition and stable UFG structure for upgrading the mechanical properties of metallic materials. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

In this study, a new medium-entropy alloy with a face-centered cubic/hexagonal close-packed (FCC/HCP) dual-phase ultrafine-grained (UFG) architecture was proposed to achieve high ductility in high-strength materials. The alloy exhibited an ultrahigh yield strength and uniform elongation at ambient temperature, attributed to the fine grain strengthening of the UFG FCC matrix and the function of deformation-induced stacking faults (SFs) in eliminating stress concentration. This work provides new guidance for upgrading the mechanical properties of metallic materials through engineering novel composition and stable UFG structure.