Microstructure and mechanical properties of AlCoxCrFeNi3-x eutectic high-entropy-alloy system

A series of AlCoxCrFeNi3-x Eutectic-High-Entropy-Alloys (EHEAs) were synthesized to investigate the effects of Co and Ni elements on the microstructure and mechanical properties. It was found that the Ni and Co elements in AlCoxCrFeNi3-x alloys could replace each other without changing the types of phases and the microstructure. All the alloys exhibited a uniform and typical eutectic microstructure with mixed structures of FeCrNi-type FCC and NiAl-type B2. The atomic percentage of (Ni + Co) of FCC phases and B2 phases in all AlCoxCrFeNi3-x alloys approximately equaled. Besides, the alloys exhibited a excellent and similar compressive properties that the fracture strength was super to 2000 MPa while the compression ratio exceeded 35%. Among the alloys, the Co-free AlCrFeNi3 alloy had the tensile yield strength of 626 MPa, the ultimate strength of 1200 MPa, and the fracture elongation of 10.1%, respectively. The tensile fracture pattern was a mixed fracture mechanism of ductile and brittle. Compare with the mechanical properties of different types of EHEAs, the FCC + B2 EHEAs have the maximum potential application in industrial areas. Therefore, it is valuable to study the cost-effective AlCoxCrFeNi3-x EHEAs.