Microstructure and ambient mechanical properties of Nb-Ti-Cr-Si based ultrahigh temperature alloy by consumable arc melting

The ingot of Nb-Ti-Cr-Si based ultrahigh temperature alloy was prepared by vacuum consumable arc melting, and the ambient mechanical properties of the alloy were measured. The results show that the chemical components are distributed uniformly at different positions of the master alloy except Cr whose concentration in the central of the ingot top is lower than that of other positions. The microstructure of the ingot is mainly composed of primary Nbss dendrites, Nbss/(Nb, X)₅Si₃ eutectic which exhibit typically lamellar or petal-like morphologies, and fine Nbss/Cr₂Nb eutectic colonies. However, some (Nb, X)₃Si are present at the top of the ingot alloy. The primary Nbss becomes coarser and directionally solidified character of Nbss/(Nb, X)₅Si₃ eutectic colonies disappear gradually from the edge to the central of the ingot. The volume of the fine Nbss/Cr₂Nb eutectic colonies is reduced. The ambient tensile strength reaches 378.7 MPa, and the ambient fracture toughness is about 13.4 MPa·m^1/2 for the Nb-Ti-Cr-Si alloy. In addition, ambient fracture mechanism is characterized by brittle quasicleavage mode in both fracture and tensile morphology.