Enhancing the yield strength of Ni–Co–Cr–Fe–Al as-cast hypoeutectic high-entropy alloys by introducing γ′ precipitation

It is still a challenge to further increase the yield strength of eutectic high-entropy alloys, a promising multiple principal alloy system. By modifying the Ni: Co ratio to introduce the γ′ phase, we developed a series of Ni_60-xCo_xCr₁₀Fe₁₀Al₁₈Mo₂ (x = 30, 20, 10, 0) casting hypoeutectic high-entropy alloys with improved yield strength and ductility. The increase of Ni concentration via decreasing Co concentration promotes the amount of FCC phase with nano γ′ particles in it. The as-cast Ni₆₀Cr₁₀Fe₁₀Al₁₈Mo₂ HEA with FCC/γ'+B2 phase composition exhibits a superior σ_0.2–831 MPa due to the formation of the γ′ phase. The results provide a feasible route for developing high-performance Ni–Co–Cr–Fe–Al casting HEAs with multiscale microstructure.