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

CrFeNiV0.5W (x) and CrFeNi2V0.5W (x) (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 CrFeNiV0.5W (x) alloys were composed of sigma, FCC, and BCC phases. Although the microstructures of the CrFeNi2V0.5W (x) alloys were still constituted by FCC, BCC, and sigma phases, the volume fraction of the FCC phase increased significantly. Dendrite morphology was also observed in the CrFeNi2V0.5W (x) alloys. With the addition of W element, the hardness of the CrFeNiV0.5W (x) alloys declined from 869 to 633 HV, while the hardness of the CrFeNi2V0.5W (x) alloys increased from 226 to 305 HV. Moreover, the CrFeNi2V0.5W (x) alloys exhibited better compressive ductility than the CrFeNiV0.5W (x) 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 CrFeNiV0.5W (x) alloys increased with the addition of the BCC-structured W elements).