Coupled bottom-up/top-down processing towards ultrafine-grained W-La2O3 alloy with hierarchical substructure and strength-ductility synergy

Tungsten (W) is regarded as a key candidate material for extreme service environments. However, its relatively high ductile-to-brittle transition temperature (DBTT) and rapid grain growth at elevated temperatures have long restricted its engineering applications. In present work, an integrated route combining bottom‑up and top‑down approaches was employed. Ultrafine W-1 wt.% La 2 O 3 powders were synthesized via a novel carbothermic pre-reduction followed by hydrogen deep deoxidation process. Subsequent hydrogen pre-sintering and spark plasma sintering (SPS) enabled rapid densification and controlled deformation at a relatively low temperature, producing a fine-grained W alloy (0.77 μm) with distinct substructural features. Nanoscale La 2 O 3 particles were uniformly distributed throughout the matrix. During high-pressure SPS, the formation of a weak γ-fiber texture ({111}//ND) promoted cooperative activity among multiple {111} 〈110〉 primary slip systems. La 2 O 3 particles located at grain boundaries effectively suppressed boundary migration through Zener pinning, while intragranular nanoparticles coordinated dislocation motion via combined Orowan bypassing and shearing mechanisms. The multiscale structural synergy enabled a favorable strength-ductility balance between 200 and 600 °C. The alloy exhibits noticeable plastic deformation at 200 °C, with distinct yielding (972.3 MPa) and uniform strain‑hardening behavior. This study elucidates the coupling among grain refinement strengthening, Orowan strengthening and dislocation forest hardening, thus providing a new design strategy for achieving high-temperature microstructural stability and mechanical reliability in W alloys.