Directional solidification of Ti-46Al-8Nb alloy in BaZrO3 coated Al2O3 composite mould

The Bridgman-type furnace was used for the directional solidification of Ti-46A1-8Nb (at.%) intermetallic alloy in Al2O3 mould with BaZrO3 protective coating. The dissolution of BaZrO3 refractory material, the effects of the spiral selector, phase composition and microstructures were investigated. The results showed that a single crystal was prepared successfully at the outlet of the spiral part due to the effects of spiral selector. However, a large columnar grain with three small grains (near single crystal) was formed during the solidification process. The angle between the lamellar direction and the growth direction was about 45' in the directional growth area. The final microstructure of Ti-46A1-8Nb alloy consisted of TiAl (gamma) and Ti3Al (alpha(2)) and no BaZrO3 phase was found. The dissolved of shell elements Ba, Y, Zr and O in the DS sample were 24 ppm, 293 ppm, 4130 ppm, 3690 ppm, respectively.