Strategically tuning oxygen in multiple phases for high-performance titanium alloys

Oxygen is traditionally detrimental to ductility in titanium alloys. Recent advances have reframed oxygen as a design tool for forming beneficial microstructures and enhancing performance. Yet, its role has been mostly limited to the α phase in dual-phase α-β titanium alloys. Introducing sufficient oxygen into β when both phases coexist may unlock beneficial motifs and improve performance. We present that strategic oxygen partitioning across coexisting α and β phases enables substantial oxygen in β and triggers a β → O' phase transformation via atomic rearrangements. This O' phase acts as a precursor for stress-induced martensitic transformation (O'→α") during deformation, activating synergistic transformation-induced and twinning-induced plasticity. The resulting α-β-O' titanium alloy (Ti-6Al-4V-0.39O) achieves an ultimate tensile strength of 1200 ± 30 MPa, ductility of 23.5 ± 1.5%, and a strength-and-strain product of 28.2 GPa·%. Our work establishes a general principle for strategically tuning oxygen in titanium alloy design and demonstrates potential for recycling oxygen-contaminated titanium waste. This study utilizes oxygen-rich Ti powders for additive manufacturing and establishes a method for strategically tuning oxygen in multiple phases in high-performance titanium alloy design which strengthens Ti-alloys with oxygen, rather than embrittling them.