Interdependent slip and twinning behaviors for improving cryogenic mechanical properties in Ti-6Al-3Nb-2Zr-1Mo alloy additively manufactured by electron beam wire-fed

α-Ti with hexagonal close-packed (HCP) structure offers exceptional strength-to-weight ratios and structural stability, becoming a promising material for extreme conditions. However, there are few reports on additively manufactured Ti alloys for cryogenic application, primarily due to the detrimental effects of porosity, inclusions, oxidation and residual stresses on mechanical performance. And the strength-ductility trade-off also challenges cryogenic applications of α-Ti alloys. This work successfully demonstrates the feasibility of electron beam wire-fed additive manufacturing (EBWF AM) for fabrication of high-performance cryogenic Ti alloys. The virtually dense Ti-6Al-3Nb-2Zr-1Mo (Ti6321) alloys exhibit yield strength of 1194 MPa and total elongation of 18.8 % at cryogenic conditions, with ∼30 % and ∼64 % improvements in ductility and strength compared to room temperature. The highly attractive cryogenic ductility is ascribed to the interdependent slip and twinning behavior in mediating cryodeformation. Specifically, the prismatic and basal 〈a〉 slips become primary deformation modes. However, the basketweave morphology benefits from more 〈c + a〉 dislocations, abundant geometrically necessary dislocations and dislocation delocalization, helping to improve cryogenic ductility and work hardening. Also, the inhibition of macro shear bands makes a contribution to the improved cryogenic ductility owing to the co-deformability of both phases and random α variants, facilitating deformation delocalization and mitigating localization effect. Instead, the sub-millimeter colonies in the fully lamellar microstructure induce more deformation twinning, while the enhanced slip lengths and planar slip propensity exacerbate strain localization and sample-scale macro shear banding, leading to premature failure. These findings highlight the superior cryogenic strength-ductility combination and important contribution of dislocation-dominated plastic cryodeformation in the basketweave microstructure. This work demonstrates the potential of EBWF for fabricating advanced structural materials for cryogenic applications and advances the understanding of Ti6321 cryodeformation behavior, offering insights for developing high-performance Ti alloys.