Dual-phase lamellar structure achieving high strength and large ductility in a novel Co-free eutectic high-entropy alloy

The design of high-performance eutectic high-entropy alloy (EHEA) is still a huge challenging in material fields. Here, we designed a dual-phase Ni₄₉Fe₂₀Al₁₇Cr₈V₆ eutectic high-entropy alloy that can be prepared by directly cast methods. The as-cast Ni₄₉Fe₂₀Al₁₇Cr₈V₆ EHEA comprises of alternating soft FCC/L1₂ and hard B2 nanolamellae, which is enriched in Fe, V, Cr elements and Ni, Al elements, respectively. Furthermore, a classical K-S orientation relationship can be established between FCC and B2 phases. Superior mechanical properties, i.e., a high yield strength of ∼790 MPa, an ultimate tensile strength of ∼1230 MPa and a large uniform elongation of ∼16.5 %, can be achieved in the as-cast Ni₄₉Fe₂₀Al₁₇Cr₈V₆ EHEA. Such excellent combination of high strength and ductility in the as-cast Ni₄₉Fe₂₀Al₁₇Cr₈V₆ EHEA mainly originates from the strong interaction of high-density dislocations in both FCC/L1₂ and B2 nanolamellae. Specifically, high-density dislocations can be effectively hindered by the phase interface between soft FCC and hard B2 lamellae, contributing a high strength. Moreover, dense L1₂ nanoprecipitates can also impede the slipping of profuse dislocations in the FCC nanolamellae, significantly enhancing the mechanical properties of the Ni₄₉Fe₂₀Al₁₇Cr₈V₆ EHEA. The result in this work provides a strong theoretical guidance for the alloy design of high-performance metals.