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 Φ9 mm polycrystalline rods with appropriate microstructure were cut from Φ70 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+α+β three-phase region, the central α phase was successfully seeding by the polycrystalline rods and gradually develops into a dominant microstructure under a bent solid-liquid interface. The selec- tion of polycrystalline seed, principle of three-phase region and bent solid-liquid interface directional solidification were discussed in detail. KEY WORDS Ti-43Al-3Si alloy, directional solidification, bent solid-liquid interface growth, op- tical floating zone furnace