Microstructure and mechanical properties of NixFeCoCrAl high-entropy alloys

The microstructure and tensile properties of NixFeCoCrAl high-entropy alloys (HEAs) were investigated. The results indicated that the microstructure of NixFeCoCrAl HEAs can be tuned from a single body-centered cubic (bcc) structure, to a bcc/face-centered cubic (fcc) eutectic dual-phase structure, and finally to a single fcc structure by increasing the Ni element content. An ultimate tensile strength of 1534 MPa was achieved in the Ni1.71FeCoCrAl HEA (N30 alloy) with a bcc/fcc dual-phase structure. On the other hand, the fcc NixFeCoCrAl HEAs with relatively-higher Ni content tend to have good ductility. Typically, the fcc Ni4FeCoCrAl HEA (N50 alloy) has a good combination of tensile strength and ductility. The underlying reasons for the achievement of high strength and large ductility of the NixFeCoCrAl HEAs were analyzed and discussed based on the chemical compositions and related microstructures.