POWDER METALLURGY OF GAMMA TITANIUM ALUMINIDES

摘要

Various high-temperature aerospace structures require low-density materials, which can survive severe environments. Gamma titanium aluminide (TiAl) alloys because of their low density (～3.9g/cm~3), good elevated temperature strength, stiffness, creep resistance, and acceptable burn and oxidation resistance have an excellent potential to supplant high density (～8.9 g/cm~3) Ni-based superalloys in high temperature aerospace applications at temperatures between 500℃ to 1000℃. Nonetheless, due to the poor intermediate and room temperature ductility of TiAl alloys, conventional manufacturing operations such as rolling, forging, or drawing are more complicated with titanium aluminides, resulting in the very high cost of TiAl components. This article will discuss the cost effective powder metallurgy approaches to manufacture flat shape (plates/sheets/foils) components of monolithic TiAl (ADMATAL-22™) and composites concepts (TiAl/Ti high-temp alloy/TiAl, TiAl/Ti_3Al/TiAl, (ADMATAL-23™) fabricated from prealloyed and blended elemental titanium powders. These components can be used in next generation launch vehicle airframe (experiencing extensive aerodynamic heating) and engine applications. Microstructures and properties of TiAl and composites will be presented and discussed.