Lamellar orientation control of directionally solidified Ti–46Al–0·5W–0·5Si alloy by self-seeding technology

Abstract

Lamellar structures of Ti–46Al–0·5W–0·5Si (at-%) alloy solidifying through the primary α phase were successfully aligned parallel to the growth direction using a self-seeding technology in a Bridgman type directional solidification furnace. At the growth rate of 20 μm s⁻¹ and temperature gradient of 12·1 K mm⁻¹, the α phase grows along the direction. Therefore, the parallel lamellar structures, whose lamellar orientation is direction, can grow continuously until the end of solidification under these solidification parameters. The original lamellar structures of the unmelted region parallel to the growth direction and suitable solidification parameters are necessary for TiAl alloys solidifying through the primary α phase to control the lamellar orientation. The self-seeding technology gets rid of the cutting and fixing of seeds and simplifies the processing of controlling the lamellar orientation of TiAl alloys. It can promote the engineering applications of the lamellar orientation control of TiAl alloys.

Keywords:

• Intermetallics
• TiAl based alloys
• Directional solidification
• Microstructure
• Lamellar orientation control

The authors are grateful to the financial support of Project 973 (grant no. 2011CB610406), Project 863 (grant no. 2012AA040208) and National Natural Science Foundation of China (grants nos. 51071062 and 50801019).