Synergistic effects of Fe and C on microstructure and properties of Nb-Ti-Si based alloys

Nb-silicide in situ composites have been considered as alternatives applied for nickel-based superalloys in aerospace field. The synergistic effects of Fe and C on microstructural evolution, properties and hot deformation behavior of Nb-24Ti-16Si-2Al-3 V-xFe-yC alloys are investigated. Results show that the microstructure of 4Fe-1 C alloy consists of Nbss/β-(Nb, X)₅Si₃ eutectics and γ-(Nb, X)₅Si₃ blocks, while the TiC particles precipitate with the increase of C content. For 6Fe-yC alloys, a new silicide phase Nb₄FeSi is formed around the (Nb, X)₅Si₃ phase. Element Fe is mainly distributed in Nb₄FeSi and part of Fe-rich (Nb, X)₅Si₃, while C is mainly dissolved in TiC particles, followed by Nbss. The orientation relationship of Nbss and TiC in accordance with {110}_Nbss//{111}_TiC. The room temperature fracture toughness and compressive strength exhibit a trend of enhancing first and then reducing with the co-addition of Fe and C. The K_Q value of the 4Fe-3 C alloy reaches the highest with a mean of 14.49 MPa·m^1/2. Element C can effectively promote the high temperature compressive strength, and Fe can improve the hot deformability. The initial eutectic coupled structure has evolved into a continuous Nbss matrix with dispersed silicides during hot deformation. Furthermore, the splitting mechanism of silicides during hot deformation is determined.