Exploring Nb[sbnd]Si based alloys with excellent fracture toughness and oxidation resistance.

The main objective of this paper is to give a comprehensive discussion of the fracture toughness and oxidation resistance of Nb-16Si-20Ti-3Al-5Cr- x Sn- y Zr (x =0.5, 1.5; y =2, 4, 6) alloys, based on experimental evidence, phase formation and diffusion theory. Results demonstrate that the microstructure of Sn 0.5 Zr 2 and Sn 1.5 Zr 2 alloys consist of Nbss and α-Nb 5 Si 3 , and the other four alloys are composed of Nbss, α-Nb 5 Si 3 and γ-Nb 5 Si 3. At the same time, the area fraction of γ-Nb 5 Si 3 increases with the increase of Zr content. The coarsening of silicides increases with the addition of Sn. The K Q value of the Sn 0.5 Zr 4 alloy reaches the highest with the mean of 12.64 MPa·m1/2. After oxidation at 800 °C for 24 h, Sn 0.5 Zr 4 alloy alloy did not undergo pest oxidation. Sn 0.5 Zr 4 alloy forms a continuous and dense TiO 2 oxide layer oxidized at 1200 °C, which makes it have the best high temperature oxidation resistance. Sn 0.5 Zr 4 alloy has excellent fracture toughness, medium temperature and high temperature oxidation resistance. • The regulation of co-doping Sn and Zr affects the type and morphology of silicides. • The Sn 0.5 Zr 4 alloy shows the best fracture toughness and its K Q value is 12.64 MPa·m1/2. • A continuous and dense TiO 2 oxide layer in Sn 0.5 Zr 4 alloy improves oxidation resistance. [ABSTRACT FROM AUTHOR]