Enhancing dynamic plasticity and adiabatic shear resistance in single-phase Ti-Zr-V-Nb-Al refractory high-entropy alloys via additive manufacturing

As-cast Ti-Zr-V-Nb-Al single-phase refractory high-entropy alloys (RHEAs) are susceptible to the premature onset of adiabatic shear localization under dynamic loading owing to their limited strain-hardening capability, which severely restricts their engineering application under impact loading conditions. To address this issue, this study employed directed energy deposition (DED) technology to fabricate a Ti-Zr-V-Nb-Al RHEA, achieving a heterogeneous grain structure consisting of alternating fine and coarse equiaxed grains, together with abundant local chemical ordering (LCO). This microstructure effectively delayed the onset of adiabatic shearing and significantly improved dynamic ductility and strain rate sensitivity. The critical strain rate for adiabatic shear band (ASB) formation increased from ∼3500 s⁻¹ in the as-cast alloy to ∼4000 s⁻¹ in the DED-fabricated alloy. In addition, at a strain rate of ∼4200 s⁻¹, the DED-fabricated alloy exhibited a dynamic yield strength of 2016 ± 28 MPa and a fracture strain of 34.6 ± 2.5%, representing increases of approximately 14.3% and 36.2%, respectively, compared with the as-cast alloy. The enhanced dynamic performance is attributed to the synergistic strengthening effects arising from the heterogeneous grain structure and LCO, which enhance the strain hardening capability and deformation homogeneity of the alloy. This study provides new insights for enhancing the dynamic strength-ductility synergy and resistance to adiabatic shear in RHEAs.