Effects of Fe Content on Microstructures and Properties of AlCoCrFe x Ni High-Entropy Alloys

The influences of added Fe element on the microstructures and properties of AlCoCrFe (x) Ni high-entropy alloys (x denoted the atomic fraction of Fe element at 0.2, 0.4, 0.6, 0.8, 1.2, 1.4, 1.6, 1.8, and 2.0) were investigated. When x = 0.2, the alloy exhibited dendrites morphology, but as the Fe content increased, the AlCoCrFe (x) Ni HEAs transformed to equiaxed grains morphology. Inside the equiaxed grains and dendritic grains, spinoidal decomposition microstructure could be clearly observed. The microstructures changed from Cr3Ni2 + B2 + BCC structures to B2 + BCC mixed structures as x exceeded 0.6, the hardness declined from HV637.2 to HV460.2, and the compressive fracture strength showed a slight decrease, whereas the plastic property showed a distinct improvement with the addition of Fe element. The maximum compression strength was 2335MPa when x = 0.2, and the maximum compression ratio was 36% when x = 2.0. The alloys transformed from paramagnetic to ferromagnetic as the content of Fe element increased, and all of the alloys exhibited soft magnetic behaviors.