A new CrFeNi₂Al eutectic high entropy alloy system with excellent mechanical properties

A low-cost Co-free CrFeNi_(3-x)Al_x (x = 1, 0.9, 0.8, 0.7, 0.6) eutectic high entropy alloy (EHEA) system was designed, successfully prepared and characterized. With the increase of Al content, the alloy dramatically transforms from a hypoeutectic to a hypereutectic microstructure together with an increase in strength and a decrease in ductility. The CrFeNi_2.2Al_0.8 alloy was found to be an eutectic high entropy alloy and was composed of face centered cubic (FCC) phase and ordered body centered cubic (B2) phase. The hypereutectic CrFeNi₂Al alloy shows excellent mechanical properties with an ultimate strength of 1357 MPa and a total elongation of 6.4% at the cast condition. The excellent mechanical properties of this EHEA system can be attributed to the nanolamellar microstructure and suggests a great potential application in the engineering field. We also propose a simple strategy to design Co-free EHEAs and predict more than ten potential Co-free EHEAs to guide experimental searches.