A new strategy for enhancing the work hardening ability and strength of FCC high entropy alloys: Simultaneously regulating the stacking fault energy and precipitated phases

High-entropy alloys (HEAs) with face-centered cubic crystal structure (FCC) usually have good ductility but relatively low strength. In this work, we propose a new strategy to address the insufficient strength of FCC structured HEAs. The strategy is carried out in two ways: (1) By reducing the stacking fault energy of alloy system to improve its work hardening ability; (2) By adjusting the content of alloying element to control the quantity of L12, σ and κ phases, thereby strengthening its matrix. Based on the above ideas, the non-equimolar Fe2CoNiVx HEAs were designed by adjusting the element content of the classic FeCoNiV HEA. The results show that Fe2CoNiV1.3 alloy has excellent work-hardening ability and strength, of which work hardening index is improved by 36 %, the yield and fracture strength are increased by 12.6 % and 40.8 % compared to FeCoNiV HEA, respectively. Additionally, the Fe2CoNiV1.3 alloy also has the best comprehensive mechanical properties. Its yield strength, ultimate tensile strength and elongation are 315.5 MPa, 724.2 MPa and 33.9 %, which is superior to the vast majority as-cast FCC structured HEAs. This study not only reduces the cost, improves the alloy's strength and toughness, but also provides ideas for the composition design of new advanced HEAs.