Exploring Nb-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-xSn-yZr x Sn- y Zr (x=0.5, 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 Sn0.5Zr2 0.5 Zr 2 and Sn1.5Zr2 1.5 Zr 2 alloys consist of Nbss and alpha-Nb5Si3, 5 Si 3 , and the other four alloys are composed of Nbss, alpha-Nb5Si3 5 Si 3 and gamma- Nb 5 Si 3 . At the same time, the area fraction of gamma- 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 Sn0.5Zr4 0.5 Zr 4 alloy reaches the highest with the mean of 12.64 MPa & sdot;m1/2. & sdot; m 1/2 . After oxidation at 800 degrees C for 24 h, Sn0.5Zr4 0.5 Zr 4 alloy alloy did not undergo pest oxidation. Sn0.5Zr4 0.5 Zr 4 alloy forms a continuous and dense TiO2 2 oxide layer oxidized at 1200 degrees C, which makes it have the best high temperature oxidation resistance. Sn0.5Zr4 0.5 Zr 4 alloy has excellent fracture toughness, medium temperature and high temperature oxidation resistance.