Refractory high-entropy alloys

Two refractory high-entropy alloys with near-equiatomic concentrations, W–Nb–Mo–Ta and W–Nb–Mo–Ta–V, were produced by vacuum arc melting. Despite containing many constituents both alloys have a single-phase body-centered cubic (BCC) structure. The lattice parameters a = 3.2134(3) Å for the quaternary alloy and a = 3.1832(2) Å for the quinternary alloy were determined with high-energy X-ray diffraction using a scattering vector length range from 0.7 to 20 Å−1. The alloy density and Vickers microhardness were ρ = 13.75 g/cm3 and Hv = 4455 MPa for the W–Nb–Mo–Ta alloy and ρ = 12.36 g/cm3 and Hv = 5250 MPa for the W–Nb–Mo–Ta–V alloy. The exceptional microhardness in these alloys is greater than any individual constituent, suggesting the operation of a solid-solution-like strengthening mechanism.