Effect of Cu addition on microstructure evolution and strength-ductility synergy of LDED Ti–Fe–Cu ternary alloys

β-stabilized titanium alloys often suffer from the trade-off between high mechanical performance and better ductility, which limits the broader industrial application. Therefore, low-alloyed Ti-2Fe-xCu alloys (x=0, 1, 2 and 3 wt.%) were fabricated by laser directed energy deposition (LDED) using blended powders as a feedstock. The effect of Cu addition on microstructural evolution and tensile properties of LDED Ti-2Fe-xCu were investigated. The as-deposited alloys exhibit mostly equiaxed prior-β grain morphology, while the room-temperature microstructure is mainly composed of a-Ti with a small amount of retained β phase and Ti 2 Cu. Compared with Ti–2Fe, Cu addition resulted in refined α laths from 1.7 μm to 0.7 μm, while Ti 2 Cu precipitates were mainly distributed in interlamellar regions. The ultimate tensile strength (UTS) increased from 740 MPa (LDED Ti-2Fe) to 800 MPa (LDED Ti-2Fe-3Cu), whereas the elongation peaked at 20% for LDED Ti-2Fe-1Cu (UTS of 760 MPa) and then declined with further Cu addition. LDED Ti-2Fe-1Cu alloy exhibited the optimal mechanical properties that the strength enhancement was primarily attributed to α-lath refinement and solid-solution strengthening, and the improved ductility was associated with the refined basket-weave α phase, and the presence of semi-coherent α/Ti 2 Cu interfaces. These results provide guidance for designing LDED Ti-Fe-Cu alloys with balanced mechanical properties for structural and biomedical applications.