A Novel BCC/B2 Structural Nb38Ti35Al15V6Cr4(TaHfMoW)2 Refractory High-Entropy Alloy with Excellent Specific Yield Strength-Plasticity Synergy

Abstract

Refractory high-entropy alloys (RHEAs) stand as promising candidates for the development of a new generation of high-temperature materials due to their exceptional mechanical properties. However, the inherent low ductility and high density of RHEAs have hindered their widespread adoption in industrial applications. In this study, an Nb₃₈Ti₃₅Al₁₅V₆Cr₄(TaHfMoW)₂ RHEA with a BCC/B2 dual-phase structure is successfully developed. The RHEA exhibits excellent specific yield strength of 162.4 MPa·g⁻¹·cm³ and 84.3 MPa·g⁻¹·cm³ at room temperature (RT) and 800 °C, respectively. It was found that the pinning effect of the B2 phase induces a gradual transition in dislocation slip mode from planar slip to cross slip, homogenizing the plastic flow and resulting in excellent compression plasticity (ε > 50%). Additionally, the B2 phase endows the alloy with excellent yield strength at high temperatures by precipitation strengthening. Moreover, the dominated a/2 < 111 > type dislocation contributes to the alloy's superior plasticity at high temperatures.