Abstract:Because of their exceptional corrosion resistance and superior low-temperature mechanical properties, titanium alloys are ideal structural materials for critical equipment operating under extreme conditions, such as Arctic resource exploitation and polar shipping routes. To further enhance low-temperature toughness and clarify the fracture–failure mechanisms of titanium alloys, a TC4-0.55Fe alloy was produced by micro-alloying with Fe, and its impact performance and fracture behavior were systematically investigated over the temperature range 20?°C toS?196?°C. The alloy exhibits a room-temperature Charpy impact toughness of 66.75?J?cm?2, which remains unchanged down to ?20?°C. When the temperature is lowered to ?70?°C, the toughness decreases to 46.75?J?cm?2, and at ?196?°C it still retains 25.1?J?cm?2—representing a 23.8?% improvement over conventional TC4. Scanning electron fractography confirms that ?196?°C is still above the alloy’s ductile–brittle transition temperature. EBSD characterization reveals abundant deformation twinning in the vicinity of the crack at all test temperatures, with twin density increasing markedly as temperature decreases. The outstanding impact toughness of the TC4-0.55Fe alloy is attributed to the synergistic effects of grain refinement, the dispersion of fine acicular α_s precipitates within the β matrix, and the pronounced rise in twin density at low temperature; together they promote crack-path deflection and significantly enhance resistance to fracture.