Strength-ductility synergism in NbTiVZr refractory high-entropy alloy driven by lattice distortion-induced electronic structure regulation

Refractory high-entropy alloys (RHEAs) exhibit significant potential for aerospace applications owing to their exceptional stability at elevated temperatures. However, the challenge of achieving density-strength-ductility synergy presents a major obstacle to engineering implementation. In this study, a strength-ductility balance is achieved through severe lattice distortion in the NbTiVZr system, which involves a larger-sized atom (Zr) and a smaller-sized atom (V). The calculated results confirm that NbTiVZr exhibits pronounced lattice distortion, which is the dominant strengthening mechanism. The localized stress fields induced by the distortion, coupled with enhanced D-orbital hybridization, significantly increase atomic bonding strength. Electronic structure analysis demonstrates that distortion promotes charge density rearrangement and transfer, further strengthening interatomic bonds. Lattice distortion also facilitates the nucleation and migration of kink bands, thereby effectively delaying crack initiation and maintaining ductility. Driven by lattice distortion, the NbTiVZr exhibits a yield strength of 1132 MPa, an elongation of 11 %, and a density of 6.47 g/cm³, achieving an exceptional balance among these three properties. This work provides a theoretical foundation for understanding how lattice distortion governs mechanical properties, offering insights for the design of low-density, high-performance RHEAs.