Designing the composition and optimizing the mechanical properties of non-equiatomic FeCoNiTi high-entropy alloys

Abstract

Research into new high-entropy alloys (HEAs) holds significant promise for advancing aerospace materials. Nevertheless, the complexity of their composition presents formidable challenges in designing HEAs with both high strength and plasticity. In this study, molecular dynamics (MD) simulation was used to explore the optimal composition combination of FeCoNiTi high-entropy alloys with non-equiatomic ratios. Shear modulus (G) characterizes strength, while stacking fault energy (SFE) characterizes plasticity and ductility. Through molecular dynamics (MD) simulations, elastic constants (C11, C12, and C44) and generalized stacking fault energies (GSFEs) for 18 alloy variants were computed. Additionally, the elastic modulus (G, E, and B) for all components was estimated using the Voigt–Reuss–Hill (VRH) averaging method. Following standard guidelines, the composition for the FeCoNiTi alloy was predicted as Ni: 30%–60 %, Co: 30%–50 %, Fe: 5%–10 %, and Ti: 5%–10 %. Subsequently, five optimized variants underwent tensile calculations to identify the most suitable composition. The results indicate that the Fe0.05Co0.4Ni0.5Ti0.05 HEA exhibits the best combination of strength and plasticity. Microscopically, its enhanced plasticity is attributed to the twinning-induced plasticity (TWIP) effect. While Fe0.1Co0.4Ni0.4Ti0.1 HEA does not outperform the other variants, it displays a martensitic transformation and deformation twins with increased strain, which are mechanisms not observed in other components. The study of non-equiatomic FeCoNiTi HEAs offers a theoretical foundation for future alloy development. This innovative alloy design method fosters the rapid development of high-performance HEAs, facilitating their rapid development and application.

Keywords

• HEAs
• Molecular dynamics
• Elastic modulus
• GSFE
• Strength-plasticity