Making high-W-content Ta-W alloys ductile via minor alloying of Hf

Ta-based refractory alloys offer excellent high-temperature strength, but high W content significantly reduces room-temperature tensile ductility. Here for Ta-14W alloy with fracture strain of ∼5%, we demonstrate that a minor Hf addition significantly improves its ductility to over 30%. Firstly, Hf induces an asymmetric core structure of screw dislocation and reduces generalized stacking fault energy (GSFE), thereby promoting dislocation mobility and dislocation multiplication during plastic deformation. Secondly, Hf can strengthen grain boundaries (GBs) by preferentially segregating near GBs. Thirdly, Hf binds with O atoms to form HfO2 particles at GBs, lowering the risk of oxygen embrittlement. All these mechanisms offer insightful guide for the development of advanced Ta-W-based refractory alloys.