REACTION-SINTERED HOT-PRESSED TIAL

Titanium aluminide intermetallic alloys and composites were formed from elemental titanium and aluminium powders by self propagating, high-temperature synthesis in an induction-heated hot-press. The crystal phases, density, transverse rupture stress, and hardness of the reaction-sintered compacts, were observed to be controlled by hot-pressing conditions. The principal phase formed was TiAl together with a significant second-phase concentration of Ti3Al. The transverse rupture strength (TRS) of the intermetallic composites was observed to vary directly with compact density. Under selected high-temperature synthesis hot-pressing conditions, TRS values were comparable to those obtained for fully dense TiAl. Titanium aluminide composites were formed by adding boron, carbon, silicon and Al2O3, and SiC powders and whiskers to the Ti-Al powders before reaction sintering. Changing the alloying additions did not have as strong an effect on properties of the composite compacts as did varying hot-pressing conditions.