TiAlbased

TiAl-based alloys are titanium aluminides, a class of intermetallic compounds that combine titanium and aluminum with small amounts of alloying elements. The gamma TiAl phase is the most commercially important, with near 40–50 at% aluminum. Additions of niobium, chromium, silicon or other elements are used to enhance creep strength, oxidation resistance, and room-temperature ductility.

Microstructure and phase stability are central to TiAl-based alloys. Structures can be tuned to fully lamellar, duplex, or near-gamma morphologies. Fully lamellar microstructures offer high high-temperature strength and creep resistance, but exhibit limited ductility at room temperature. Duplex structures provide a balance between strength and ductility, while near-gamma aids formability. The ordered gamma phase (L21/L10–like ordering) contributes to high-temperature stability.

Properties and performance are highly favorable for weight-sensitive applications. TiAl-based alloys are significantly lighter than nickel-based superalloys, with densities around 4.0–4.5 g/cm3 and good specific strength. They maintain mechanical strength to elevated service temperatures (often in the 600–800 C range, depending on composition and coatings). However, room-temperature ductility and fracture toughness are limited, and oxidation resistance requires protective coatings; machining and repair can be more challenging than for conventional metals.

Processing and manufacturing methods include investment casting, directional solidification, and powder metallurgy techniques such as hot isostatic pressing. Conventional hot working and heat treatments tailor the microstructure for target properties. Coatings and surface treatments are commonly employed to improve high-temperature oxidation resistance and component life.

Applications and outlook focus on aerospace and other weight-critical sectors. TiAl-based alloys are used for turbine blades and vanes, exhaust components, and other high-temperature, low-weight parts. Ongoing research aims to further improve ductility, oxidation resistance, and cost through new alloy compositions and processing routes.