Directional solidification of TiAl-base alloys

Mechanical properties of the lamellar microstructure of TiAl-base alloys are extremely anisotropic with respect to the lamellar orientation. However, if the lamellar microstructure can be aligned parallel to the growth direction, the resulting material should possess a good combination of strength and ductility. Unfortunately, simple casting operations often lead to a solidification texture with the lamellar boundaries all perpendicular to the heat flow direction. This difficulty can be overcome by directionally solidifying TiAl-base alloys. We have been performing directional solidification experiments with and without using a seeding technique. The current status of directional solidification of TiAl-base alloys is reviewed.