Sub-10-nm stacking bands enable ultrastrong additively manufactured titanium

Lightweight alloys with superior strength-ductility synergies are crucial for advanced structural applications, and nanostructured titanium (Ti) alloys are promising candidates. However, it remains challenging to manufacture bulk components with complex geometries as well as preserving the nanostructure and associated excellent mechanical properties. Here we report an ultrastrong Ti alloy fabricated by laser powder bed fusion, with composition and processing parameters optimized using the high-throughput experiments and machine learning method. This route yields a microstructure consisting of sub-10-nm stacking bands driven by martensitic transformation within a previously inaccessible composition-processing regime. This nanostructured microstructure endows the Ti alloy with a yield strength of ~1.5 GPa, an ultimate tensile strength exceeding 1.7 GPa, uniform elongation of ~7.5% and specific strength of ~380 MPa cm³ g^‒1. The developed Ti alloy combines high strength, ductility and scalable manufacturing, offering a promising combination of properties for structural applications.