Synchronous enhancement of hot deformation capacity and properties of Nb-24Ti-16Si-2Al alloy by composite alloying of Fe and V

To improve the thermal deformation ability of Nb-Si alloy whilst increasing the comprehension properties, the synergistic effects of Fe and V on microstructural evolution and properties of Nb-24Ti-16Si-2Al alloys are investigated. Results show that with the co-addition of Fe and V, the formation of (Nb, X)₃Si is suppressed and a new silicide Nb₄FeSi is obtained. The constituent phases of the alloys transform from Nbss + β-(Nb, X)₅Si₃ + (Nb, X)₃Si to Nbss + β-(Nb, X)₅Si₃ + Nb₄FeSi. Element Fe is primarily enriched in Nb₄FeSi phase, while V is mainly dissolved in Nbss and Nb₄FeSi phases. The room temperature fracture toughness is significantly enhanced by the co-addition of Fe and V, in which the K_Q value of 2Fe-5V alloy reaches 12.87 MPa m^1/2, improved by 96.2% compared with the initial alloy. Hot deformation behavior is sensitive to composition and temperature, and an excellent hot deformation ability is exhibited as close to the melting point of Nb₄FeSi (1348 °C). After hot deformation, the composition homogenization is achieved and the Nbss/β-(Nb, X)₅Si₃ eutectics have evolved into a continuous Nbss matrix with dispersed β-(Nb, X)₅Si₃ particles. The Fe enrichment region will become the source of the splitting of (Nb, X)₅Si₃ during hot deformation, resulting in the fragmentation and refinement of the coarse silicides.