Precise design strategy of FeNiCrMo eutectic high-entropy alloys

A group of low-cost Fe40Ni(50-x)Cr10Mox high-entropy alloys (HEAs) without the Co element were proposed. The microstructure and properties were investigated. With the increase of Mo content, the microstructure changes from FCC single-phase to two-phase divorced eutectic, divorced eutectic + hypoeutectic, hypoeutectic, eutectic and hypereutectic, in which the two-phase is composed of FCC phase + σ phase. The yield strength of alloy increases with the increase of Mo content. Its strengthening mechanism transforms from solution strengthening to second phase strengthening and grain boundary strengthening. Mo-20 and Mo-22.5 have comprehensive mechanical properties, and their yield strength, fracture strength and plastic strain are 1103.1 MPa and 1127.9 MPa, 1924.5 MPa and 1881.7 MPa, 30.4% and 28.7% respectively. In addition, the revised equivalent Cr content (ECC) is proposed in the FeNiCrMo HEAs, ECC = at.%[Cr]+8/3 × at.%[Mo]. The eutectic composition can be precisely designed through the revised ECC and atomic content ratio (RI/F) of the intermetallic forming elements to the FCC forming elements in FeNiCrMo HEAs system. When 20 at.%≤Fe and Ni ≤ 40 at.%, and RI/F = ECC/[x × at.%Fe + y × at.%Ni] = 1.05 ± 0.3, FexNiyCrmMon is the eutectic high-entropy alloy.