Dual inverse-gradient nanostructured BCC tungsten for synergistic strength-ductility enhancement via dislocation dynamics

Body-centered cubic (BCC) metals are frequently limited by intrinsic strength-ductility trade-off, constraining their utility in structural applications. While gradient nanostructures offer a potential solution, conventional designs suffer from thermal and mechanical instability due to surface-nanograins coarsening under operational stresses. In this study, we demonstrate an inverse-gradient nanostructural design in BCC tungsten wires, featuring dual radial gradients in grain size and nanoprecipitate dimensions. The wires exhibit exceptional mechanical performance with 6.92 GPa tensile strength and 4.2 % fracture elongation, enhanced by 20 % and 75 % compared to equiaxed nanograined (NG) wires. Furthermore, it is demonstrated that increasing the gradient scale further strengthens these synergistic effects. Atomic-scale characterization and molecular dynamics (MD) simulations reveal the enhancement mechanism of dislocation dynamics, where distinct cross-sectional dislocation distributions effectively transfer strain localization from surface to bulk. This strain-gradient-mediated dislocation dynamics establishes a microstructure-property relationship that transcends conventional strength-ductility compromise, providing a universal design strategy for engineering high-performance BCC metals with tailored stability for extreme-environment applications.