Microstructure and mechanical properties of CuCrFeNi medium entropy alloys synthesized via mechanical alloying and spark plasma sintering

In this study, two novel Co-free medium entropy alloys (MEAs) with compositions of Cu20Cr10Fe35Ni35 (Cu20) and Cu10Cr20Fe35Ni35 (Cu10) were successfully prepared by a combination of mechanical alloying (MA) and spark plasma sintering (SPS). The Cu20 alloy exhibited a heterogeneous microstructure consisting of coarse and ultrafine grains (UFG) with a face-centered cubic (FCC) structure. In contrast, the Cu10 alloy showed a homogeneous UFG microstructure with an FCC matrix and a small amount of BCC phase. Moreover, both alloys contained a small amount of Cr7C3 particles, introduced by milling media during MA. In comparison with the Cu20 alloy, the Cu10 alloy exhibited better tensile properties, e.g., yield strength of 712 MPa, ultimate tensile strength of 843 MPa, and elongation of 20.1 %, demonstrating an excellent balance between strength and ductility compared to some well-established FCC-structured multi-component MEAs and high entropy alloys (HEAs). The enhanced tensile properties of the Cu10 alloy are attributed to the synergistic effects of grain refinement and Orowan strengthening by the fine Cr7C3 particles. The findings of this work provide valuable insights for designing cost-effective HEAs and MEAs with high strength and desirable ductility for various structural applications. •Co-free non-equiatomic CuCrFeNi MEAs were prepared by mechanical alloying & spark plasma sintering.•MEAs exhibited fine-grained microstructure with a submicron order.•MEAs showed homogeneous or heterogeneous microstructure, depending on Cu content.•MEAs exhibited a superior strength-ductility balance compared to some FCC H/MEAs.•The MEA with low Cu amount resulted in improved yield strength & tensile strength.