A Novel Low-Activation VCrFeTa(x)W(x) (x = 0.1, 0.2, 0.3, 0.4, and 1) High-Entropy Alloys with Excellent Heat-Softening Resistance

The microstructure, Vickers hardness, and compressive properties of novel low-activation VCrFeTa(x)W(x) (x = 0.1, 0.2, 0.3, 0.4, and 1) high-entropy alloys (HEAs) were studied. The alloys were fabricated by vacuum-arc melting and the characteristics of these alloys were explored. The microstructures of all the alloys exhibited a typical morphology of dendritic and eutectic structures. The VCrFeTa(0.1)W(0.1) and VCrFeTa(0.2)W(0.2) alloys are essentially single phase, consisting of a disordered body-centered-cubic (BCC) phase, whereas the VCrFeTa(0.2)W(0.2) alloy contains fine, nanoscale precipitates distributed in the BCC matrix. The lattice parameters and compositions of the identified phases were investigated. The alloys have Vickers hardness values ranging from 546 HV(0.2) to 1135 HV(0.2) with the x ranging from 0.1 to 1, respectively. The VCrFeTa(0.1)W(0.1) and VCrFeTa(0.2)W(0.2) alloys exhibit compressive yield strengths of 1341 MPa and 1742 MPa, with compressive plastic strains of 42.2% and 35.7%, respectively. VCrFeTa(0.1)W(0.1) and VCrFeTa(0.2)W(0.2) alloys have excellent hardness after annealing for 25 h at 600–1000 °C, and presented compressive yield strength exceeding 1000 MPa with excellent heat-softening resistance at 600–800 °C. By applying the HEA criteria, Ta and W additions into the VCrFeTaW are proposed as a family of candidate materials for fusion reactors and high-temperature structural applications.