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

Abstract

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 Ni60-xCoxCr10Fe10Al18Mo2 (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 σ0.2–831 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.