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The superplastic tensile behaviors and mechanisms of Ti6Al4V alloys and TiBw/Ti6Al4V composites with tailored architecture were comparatively studied in order to reveal the superplasticity mechanisms. The superplastic tensile tests were carried out at the temperatures of 900 °C, 925 °C, 950 °C and 975 °C with the strain rate of 0.000316/s, 0.001/s and 0.00316/s, respectively. The composites exhibited higher superplasticity, higher strain rate sensitivity index m and lower activation energy Q than the alloys. This might be attributed to the small lamellar aspect ratio and TiBw reinforcement addition. Microstructural observation showed that the aspect ratio of α phase in the Ti6Al4V alloys decreased with increasing strains, and transferred to equiaxed grains only in the tip area. Therefore, necking could not be constrained and transferred to other positions with unfavorable microstructure, led to the needle-like fracture …