Directional solidification of TiAl base alloys using a polycrystalline seed

Lamellar microstructure control and characterization of directionally solidified (DS) Ti-43Al-3Si alloys have been studied. The DS alloys were obtained using a polycrystalline seed at a growth rate of 5 mm h(-1) under the plane front solidification condition. The DS ingots not only have fully lamellar microstructure parallel to the longitudinal axis but also possess rotated columnar grains with respect to the longitudinal axis. Any defects in crucible or equiaxed grains of the seed can cause unaligned lamellar microstructure. Pole figure measurements for lamellar microstructure showed that ND (101) texture was dominant in the aligned part, and ND (212) and ND (111) texture were found in the unaligned part of the DS ingot. (C) 2002 Elsevier Science B.V. All rights reserved.