Lamellar orientation and growth direction of α phase in directionally solidified Ti-46Al-0.5W-0.5Si alloy

Directional solidification experiments were performed on intermetallic Ti-46Al-0.5W-0.5Si (at. %) alloy using a Bridgman-type furnace. Lamellar orientation and growth direction of α phase under different growth rates were studied. The hexagonal α phase is the primary phase of the alloy. The lamellar orientations are inclined at the angles of 80°-90° to the growth direction at growth rates below 10 μm/s. With increasing growth rate, the lamellar orientations are changed and not perpendicular to growth direction. When growth rates are below 10 μm/s, the preferred growth direction (PGD) of α dendrites is <0001> direction. The PGD of α phase changes into <112¯0> direction when growth rate increasing to 20 μm/s. Besides, The PGD of α phase is changed into<2¯2¯43> direction at growth rates of 30 μm/s and 50 μm/s. The lamellar orientation can be aligned to the growth direction when the PGD of α phase is<112¯0> direction.