Liquid-phase separation occurred in CoCrCuxFeMoNi (x ≥ 0.5) alloys when the mixing entropies are positive in our previous work. So in this work, CoCr0.5CuxFeyMoNi alloys are designed to investigate the microstructure, component phases and properties. FCC and BCC were detected in CoCr0.5CuxFeyMoNi alloys, accompanied with a topologically close-packed μ phase. A parameter, VR, was defined, where VR is the ratio of the volume fraction of BCC plus μ phases and that of FCC phase. The maximum strength and the ductility were obtained at the minimum VR of the alloys, whereas the hardness increased with the increasing VR. It can be presumed that the strange balance between strength, ductility and hardness is an indirect result of the degree of brittle failure.
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