Effects of Tungsten on Microstructure and Mechanical Properties of CrFeNiV0.5Wx and CrFeNi2V0.5Wx High-Entropy Alloys

CrFeNiV0.5Wx and CrFeNi2V0.5Wx (x = 0.25, 0.5, 0.75, and 1.0) high-entropy alloys were prepared by vacuum arc melting. The effects of W element on the microstructures and mechanical properties of these alloys were investigated. The experimental results indicated that the CrFeNiV0.5Wx alloys were composed of σ, FCC, and BCC phases. Although the microstructures of the CrFeNi2V0.5Wx alloys were still constituted by FCC, BCC, and σ phases, the volume fraction of the FCC phase increased significantly. Dendrite morphology was also observed in the CrFeNi2V0.5Wx alloys. With the addition of W element, the hardness of the CrFeNiV0.5Wx alloys declined from 869 to 633 HV, while the hardness of the CrFeNi2V0.5Wx alloys increased from 226 to 305 HV. Moreover, the CrFeNi2V0.5Wx alloys exhibited better compressive ductility than the CrFeNiV0.5Wx alloys. This study was the first known incidence in which the FCC phase increased in the HEAs with a decrease of the valence electron concentration (VEC) value (i.e., the FCC phase of the CrFeNiV0.5Wx alloys increased with the addition of the BCC-structured W elements).