Rapid Design, Microstructures, and Properties of Low-Cost Co-Free Al-Cr-Fe-Ni Eutectic Medium Entropy Alloys

In this study, we establish a mathematical rule for accelerating the prediction of low-cost Co-free AlCr(a)Fe(b)Ni(c) FCC/B2-structured eutectic medium entropy alloys (EMEAs). The mathematical formulas are c ≥ 1.0, 4.38a + 4.28b + 3.97c ≈ 20.55, and c − a ˃ 1.0. With this rule, we successfully predict the AlCr(1.18)FeNi(2.8) and AlCrFe(1.46)Ni(2.5) eutectic alloys and verify their eutectic morphology by experiments. Both the AlCr(1.18)FeNi(2.8) and AlCrFe(1.46)Ni(2.5) EHEAs exhibit excellent compressive mechanical properties, with yield stress higher than 500 MPa, compressive fracture strength higher than 2450 MPa, and fracture strain > 40%, which can be attributed to their unique lamellar microstructure. Moreover, both alloys exhibit good corrosion resistance in 3.5 wt.% NaCl solution. Among them, the AlCr(1.18)FeNi(2.8) EHEA exhibits better corrosion resistance due to the higher content of the FCC phase.