D0_(22) precipitates strengthened W-Ta-Fe-Ni refractory high-entropy alloy

Refractory high-entropy alloys have recently emerged as promising candidates for high-temperature structural applications.However,their performance is compromised by the trade-off required between strength and ductility.Here,a novel W30Ta5(FeNi)65 refractory high-entropy alloy with an outstanding combination of strength and plasticity at both room and elevated temperatures is designed,based on the multi-phase transitions design strategy.The alloy comprises a body-centered cubic dendrite phase,a topologically close-packed μ rhombohedral phase,and a high-density coherent nano-precipitate γ"phase with the D0_(22)structure(Ni3Ta type)embedded in a continuous face-centered cubic matrix.Owing to pre-cipitation strengthening of D0_(22),the yield stress of the alloy is determined as high as 1450 MPa,which is a significant improvement(~100%)in comparison with the D0_(22)-free alloy,without a loss of ductil-ity.This alloy exhibits an excellent high-temperature strength,with the yield strengths of 1300 MPa at 600 ℃ and 320 MPa at 1000 ℃.Detailed microstructural characterization using transmission electron mi-croscopy,high-angle annular dark-field imaging,and three-dimensional atom probe tomography analyses indicated that this superior strength-plasticity combination stems from the synergy of a multiple-phase structure.These results provide a new insight into the design of RHEAs and other advanced alloys.