Development of the γ′ phase strengthened high-temperature high-entropy alloys with excellent mechanical properties

[Display omitted] •A series of nano-size γʹ-strengthened HEAs have been fabricated successfully.•The effects of doping elements on HEAs were systematically explored.•The strengthening mechanisms of the HEAs have been systematically studied. In this work, a series of novel γ' phase strengthened Ti6Al6-based HEAs with six kinds of alloying elements (including Nb, Hf, Ta, W, Mo, and V) were carefully examined combined with TEM, SEM, XRD, and DSC technologies. The impurities Fe2X (X = Nb, Hf, and Ta) Laves were detected in the Nb-, Hf- and Ta-doping alloys while the other three present a perfect (γ + γ') dual-phase microstructures. And the W-, Mo- and V-doping HEAs possess a much better strength-plasticity combination than the Ti6Al6 alloy at room- and high-temperature. The 1.5 W HEA has a tensile strength of ∼ 1300 MPa and good plasticity (>30 %) at room temperature. In the meantime, it also performs much good at 800 °C (∼11 % elongation and the tensile strength of ∼ 750 MPa). The addition of W, Mo, and V elements causes the main peak of the HEAs to shift to the left to varying degrees, among which the biggest shift is 1.5 V HEA, followed by 1.5Mo HEA, the smaller is the 1.5 W HEA. At the same time, the γ' precipitates phase of the alloy has a highly coherent relationship with the FCC matrix phase, which ensures that the strength of the alloy is increased without sacrificing its plasticity.