Directional solidification experiments were performed on the intermetallic Ti-46Al-0.5W-0.5Si (at%) alloy using a Bridgman-type furnace. The effect of growth rate on the solidification behavior and microstructure parameters was determined. After directional solidification, the microstructure is composed of alpha(2)/gamma lamellar structures and fine Ti(5)Si(3) precipitates. During the solidification process, W segregates into dendritic cores of a phase, and Si segregates into interdendritic regions. The enrichment of Si leads to the formation of Ti(5)Si(3) phases. The primary dendritic arm spacings and interlamellar spacings decrease with the increasing growth rate. Because of the change of preferred growth direction (PGD), the lamellar orientation is not perpendicular to the growth direction, even if the alpha phase is the primary phase. The variation of lamellar orientation can be attributed to two factors. One is the history-dependence on the lamellar orientation of unmelted as-cast crystals near the initial interface of directional solidification. The other is the variation of PGD of the alpha phase. With the increasing growth rate, the variation of PGD of alpha phase is as follows: < 0001 > -> < 10 (1) over bar1 > -> <(2) over bar(2) over bar 43 > -> < 10 (1) over bar1 >. (C) 2011 Elsevier B.V. All rights reserved.