Effect of Ni on Microstructures and Mechanical Properties for Multielemental Nb–Si-Based Alloys

Eight-element Nb–Si alloys (Nb–Si–Ti–Cr–Al–Hf–Zr–Ni) with different Ni contents were prepared by arc melting to obtain Nb–Si alloys with high mechanical properties. Phase selection, microstructure evolution, room-temperature fracture toughness, and compressive properties were investigated systematically. Results showed that the eutectic Nb–Si alloy becomes a hypereutectic Nb–Si alloy with the increase in Ni content. All alloys contain Nbss, γ-(Nb, X)₅Si₃ and Cr₂(Nb, X) phases, and 2Ni and 3Ni alloys also contain the primary α-(Nb, X)₅Si₃ phase. With the increase in Ni content, the content and size of the primary α-(Nb, X)₅Si₃ phase increased. K_Q first increased and then decreased, with the highest K_Q of 12.6 MPa m^1/2 occurring in the 2Ni alloy. The room-temperature maximum compressive strength was improved with 1 at. pct Ni addition but decreased with higher Ni addition. The strengthening mechanism is solid solution strengthening and a high content of the γ-(Nb, X)₅Si₃ phase by Ni element addition.