GammaTiAl

Gamma-TiAl, or gamma titanium aluminide, is an intermetallic compound composed of titanium and aluminum that crystallizes in the gamma phase, a long-range ordered structure related to the L1_0 tetragonal family. The alloy is near equiatomic TiAl, commonly formulated with small amounts of alloying elements such as niobium, chromium, or silicon to improve mechanical performance and oxidation resistance.

Typically, gamma-TiAl alloys exhibit a two-phase microstructure consisting of gamma grains with lamellar or duplex morphologies that combine gamma with alpha2-Ti3Al. Such structures enhance high-temperature strength and creep resistance compared with simple gamma-only material. Alloying additions and thermomechanical processing are used to control phase balance, grain size, and lamella thickness.

Key properties include a low density around 3.8–4.0 g/cm3 and a high melting temperature near 1250–1260°C, yielding good strength at elevated temperatures and improved specific stiffness. The alloys show excellent oxidation resistance when properly coated or doped, but they remain comparatively brittle at room temperature and can exhibit limited fracture toughness and formability, especially in uncooled conditions.

Manufacturing techniques include investment casting, directionally solidified casting, and powder metallurgy, followed by heat treatments to develop desired gamma/alpha2 microstructures. Processing windows are narrow, and machining is difficult due to high hardness and low ductility, increasing component cost. Research continues to improve hot-workability, manufacturability, and environmental durability.

Gamma-TiAl alloys are used in aerospace and automotive applications where weight savings and high-temperature performance are advantageous. Notable uses include valve seats in high-performance engines and certain turbine or compressor components, as well as structural parts in engines and airframes, where density is lower than conventional nickel-based alloys.