Phase-engineering-based design enables exceptional strength-ductility synergy in additively manufactured titanium alloys

In the additive manufacturing of alloys, the formation of coarse grains and metastable phases often affects the strength-ductility synergy of printed materials. To overcome this challenge, we propose a phase engineering approach. Using Ti64 alloy as a model, we eliminate metastable phases to improve toughness by employing β-phase isomorphous elements (using Mo), and refine the grains to enhance strength by using ceramic-based nucleating agents (using TiC). The resulting Ti64-Mo-TiC titanium matrix composite exhibits exceptional tensile properties, achieving a tensile strength of 1561 MPa and a 24.3 % improvement in elongation compared to Ti64. The increased strength is attributed to the load-bearing capacity of TiC particles and grain refinement-induced strengthening, while the enhanced elongation is ascribed to the Mo addition and the coherent interfaces between TiC and the matrix, which facilitate dislocation transfer. This study presents an innovative phase engineering strategy to advance the fabrication and application of materials with superior strength-ductility synergy.