Abstract:The cross piercing (RP) TC4-0.55 Fe titanium alloy seamless tube was taken as the research object. The microstructure was controlled by solid solution and aging treatments. The tensile properties at room temperature and impact properties at –20 ℃ were tested. The effects of microstructure evolution on mechanical properties were analyzed by scanning electron microscope, X-ray diffractometer, and transmission electron microscope. The results show that the size of αC and the average grain thickness of αL increase significantly, and the orientation and uniformity of the microstructure are also significantly enhanced. The tensile strength, yield strength, and elongation of RP samples are 904±1.23 MPa, 793±2.62 MPa and (14.2±0.72)%, respectively. The impact energy and impact toughness at –20 ℃ are 66.2±1.62 J and 82.7±1.03 J/cm2, respectively. After solution and aging in the two-phase region, the tensile strength, yield strength, and elongation of STA910 sample increase to 984±8.92 MPa, 904±9.93 MPa and (16.2±0.93)%, respectively. The impact energy and impact toughness at –20 ℃ decrease slightly, but still maintain at 52.8±1.77 J and 64.9±1.78 J/cm2, respectively. The α/β interface is increased by the precipitation of αS and ω phases in the STA910 sample, which increases the dislocation slip and motion resistance and improves the segregation of alloying elements. The dual effects of grain boundary strengthening and solid solution strengthening are achieved, thus improving the strength and plasticity of the alloy. On the other hand, all TC4-0.55Fe alloys show excellent impact toughness. The fracture modes of the alloys are mainly ductile fracture and transgranular fracture. The coarsening of α phase grain size, the decrease in β phase stability, and the precipitation of αS and ω phases in βt lead to the decrease in impact properties of the alloys.