Additive manufacturing of ductile refractory high-entropy alloys via phase engineering

Abstract

Refractory high-entropy alloys (RHEAs) are developed for superior elevated-temperature strength and softening resistance. Additive manufacturing of RHEAs is attracting extensive attention because of their commendable potential in many applications. Yet, most additively manufactured RHEAs are brittle and their tensile properties at room temperature have rarely been reported. Here, tensile ductile RHEAs are fabricated by laser melting deposition for the first time. In the model TiZrHfNbx (x = 0.6, 0.8, 1.0, in molar ratios) RHEAs, the as-printed alloys have an equiaxed-grained microstructure without any special process control or additional treatment. Increasing Nb contents stabilizes the body-centered cubic phase and suppresses the ω phase formation. Such phase engineering strategy transforms the mechanical performance from brittle to ductile fracture. As a result, the as-printed TiZrHfNb variant exhibits a room temperature tensile yield strength of ∼1034 MPa and ductility of ∼18.5%. The solid-solution strengthening contributes to the high tensile yield strength, the local chemical fluctuations promote dislocation interactions and give rise to the large ductility. This work offers a new avenue for additive manufacturing of ductile RHEAs, which is conducive to their industrial application.