Inducing α^″ phase by interstitial carbon atoms to achieve strength-ductility enhancement in as-printed Ti alloy

Intermediate α^″ phase was constructed in as-printed Ti alloys by introducing interstitial carbon atoms to mitigate the detrimental effects of α′ martensite on ductility. The interstitials served as a lattice modulation limiter to achieve an incomplete atomic shuffle during martensitic transformation process to form metastable α^″ phase, followed by stabilizing the α^″ to inhibit the growth of α′ martensite. The resulting microstructure, characterized by a dominant α/α′ matrix decorated with fine α^″ phase, enhanced twinning formation ability and induced dynamic Hall–Petch and grain refinement strengthening effects. This resulted in simultaneous improvements in both strength and ductility.