Lamellar orientation control in directionally solidiifed TiAl intermetallics

摘要

TiAl-based aloys are potentialy used as high-temperature structural materials with a high speciifc strength in the range of ~ 900°C. However, the mechanical properties of TiAl-based aloys are extremely anisotropic with respect to the lamelar orientation of the microstructures. A balance combination of room-temperature ductility and strength can be achieved when the lamellar orientation are aligned parallel to the tensile stress direction. Lamelar orientation control of TiAl-based aloys by directional solidiifcation technique has been widely studied in recent years. Two different directional solidiifcation processes can be used to modify the lamelar orientation. One is a seeding technique and the other is adjusting the solidiifcation path. This paper reviews the principles of the two methods and their progress. The inlfuence of aloy composition and solidification parameters on lamellar orientation control is also discussed.