DIRECTIONAL SOLIDIFICATION OF Ti-43Al-3Si ALLOYS IN AN OPTICAL FLOATING ZONE FURNACE

Directional solidification (DS) process of Ti-43Al-3Si alloys in an optical floating zone furnace has been studied. The Phi 9 mm polycrystalline rods with appropriate microstructure were cut from Phi 70 mm cast ingot and used as seeds. At a growth rate of 5 mm/h, the DS ingot with lamellar structure parallel to longitudinal axis was obtained. The results of OM show that in the L+alpha+beta three-phase region, the central alpha phase was successfully seeding by the polycrystalline rods and gradually develops into a dominant microstructure under a bent solid-liquid interface. The selection of polycrystalline seed, principle of three-phase region and bent solid-liquid interface directional solidification were discussed in detail.