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

Abstract

• 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 Fe 2 X (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.