JOINING OF THE INTERMETALLIC COMPOUND TIAL USING SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS REACTION

The intermetallic compound TiAl was bonded by using self-propagating h igh-temperature synthesis (SHS) reaction of a mixture of elemental Al and Ti powders used as a filler metal. The structure of SHS reacted fi ller metal was inhomogeneous and consisted of Ti, alpha(2) (Ti3Al) and TiAl3. On the bonding interface between base metal and filler metal, TiAl3 was formed as a reaction layer. By the subsequent heat treatment of the SHS joint at 1573 K, the structure of the filler metal changed to a fine lamellar structure consisting of alpha(2) and gamma (TiAl) phases. The TiAl3 reaction layer, however, did not transform to a lame llar structure but only to a single-phase gamma. Joint strength at roo m temperature and at 873 K exhibited about 220 MPa which was about the same as that of the base metal.