Mechanism study on microstructure and mechanical properties of TiBw/TC4 composite materials regulated by Bi element

This study fabricated (TiBw–Bi)/TC4 composites featuring a three-dimensional network reinforcement architecture via low-energy ball milling followed by vacuum hot-press sintering (950–1000 °C). By tailoring the nanoscale TiB₂ content and introducing micron-scale bismuth (0.125, 0.25 and 0.5 wt%), the effects of Bi addition and sintering temperature on reinforcement evolution, interfacial behavior, matrix grain characteristics, and room-temperature tensile performance were systematically investigated. The composite containing 0.125 wt% Bi and sintered at 1000 °C exhibited the best tensile performance, with an ultimate tensile strength of 1103 MPa and an elongation of 6.2%. Microstructural and phase analyses suggest that liquid Bi at elevated temperature promotes the in-situ formation of TiBw and the precipitation of Ti₂Bi. In addition, Bi addition was associated with finer α-Ti grains and a more continuous reinforcement network. Overall, the results show that a small Bi addition is effective in tailoring the microstructure and tensile properties of TiBw/TC4 composites.