Abstract: Designing precipitation-strengthened FCC/B2 dual-phase high-entropy alloys promotes the development of structural materials with high mechanical performance and lower density. In the present work, Ti and Ta were utilized as alloying elements in a Ni_43.9Co₁₉Cr₁₀Fe₁₀Al₁₅Mo₂B_0.1 alloy to concurrently enhance the precipitation strengthening in both the FCC and B2 phases. In the FCC phase, the alloying elements increased the volume fraction of L1₂ precipitates and anti-phase boundary energy, thereby enhancing the precipitation-strengthening effect. In the B2 phase, the alloying elements promoted the formation of FCC-structured precipitates with refined inter-precipitate spacing and thus improved the Orowan strengthening contribution. With the harder B2 phase, the more significant hetero-deformation-induced hardening enhanced the alloy strain hardenability. Although ductility decreased, the continuous stacking fault glides and phase transformations in the FCC-structured precipitates contributed to the strength-ductility synergy by preventing intragranular cracking and mitigating crack propagation in the B2 phase. These findings provide valuable insights for the future design and development of precipitation-strengthened FCC/B2 dual-phase high-entropy alloys.

Key words: Dual-phase high-entropy alloy, Microalloying, Precipitation hardening, Deformation mechanisms, Strength-ductility synergy