What grades of titanium are used in aerospace
In the aerospace sector, titanium alloys have become irreplaceable key materials due to their unique physical and chemical properties, such as low density, high strength, corrosion resistance, and high-temperature resistance. From fighter jet fuselages to satellite brackets, from rocket engine turbine blades to manned spacecraft cabins, titanium alloys are used throughout every aspect of aerospace equipment.
Commercially Pure Titanium
Commercially Pure Titanium (CP series) is one of the earliest titanium alloys used in aerospace. It is primarily composed of hexagonal close-packed (HCP) α phase, with a small amount of β phase. Based on tensile strength, commercially pure titanium is divided into four grades: G1, G2, G3, and G4. Higher grades indicate higher oxygen concentrations, which promote intermittent solid solution strengthening, and thus higher strength. Commercially pure titanium has excellent corrosion resistance and weldability, but relatively low strength. Therefore, it is primarily used in the manufacture of non-load-bearing components, such as air heating pipes for wing leading edge de-icing systems, cabin environmental control system piping, hydraulic piping, and various clamping and support devices.
Alpha Titanium Alloys
Alpha titanium alloys enhance their strength and heat resistance by adding alpha-stabilizing elements (such as aluminum) and neutral alloying elements (such as tin). Ti-5Al-2.5Sn ELI (Elite Life Inertial) is one of the most common alpha titanium alloys used in aerospace applications. By reducing the interstitial element content of conventional Ti-5Al-2.5Sn, it significantly improves its strength and toughness at extremely low temperatures. This alloy maintains good toughness and low thermal conductivity even at temperatures as low as 20K (-250°C), making it widely used in cryogenic vessels, cryogenic piping, and components such as liquid rocket engine turbofuel pump impellers.
Near-Alpha Titanium Alloys
Alpha titanium alloys are not as strong as alpha+beta or beta alloys at room temperature, but they exhibit superior high-temperature creep resistance. These alloys primarily contain aluminum, tin, and zirconium, along with small amounts of low-diffusivity beta-stabilizing elements (such as molybdenum or niobium), enabling them to maintain sufficient strength at high temperatures.
α+β Titanium Alloys
α+β titanium alloys are by far the most widely used type of titanium alloy. They contain a higher content of beta, allowing for even higher strength through heat treatment. Among them, Ti-6Al-4V (TC4/GR5) is the most representative α+β titanium alloy, accounting for over 60% of titanium used in aerospace. This alloy boasts excellent overall properties, including high strength, good weldability, and formability, making it widely used in key components such as fuselage frames, engine fan blades, and landing gear. In addition, alloys such as Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.2Si (6-2-2-2-2S) are also widely used in aerospace due to their excellent properties.
β-Titanium Alloys
β-Titanium alloys have excellent cold forming capabilities and can be heat treated to achieve extremely high strength. These alloys are primarily used in aerospace structural components with high strength requirements, such as aircraft landing gear components. For example, Ti-10V-2Fe-3Al (TB6), a high-strength, high-toughness near-β titanium alloy, boasts high specific strength, excellent fracture toughness, and a large through-hardening area, making it suitable for manufacturing structural components with high strength and fracture toughness requirements. In addition, alloys such as Ti-15V-3Cr-3Al-3Sn (T15-3-3-3) are also used in the aerospace field due to their excellent rolling and cold formability.
Titanium-aluminum alloys
Titanium-aluminum alloys are alloys containing various intermetallic compounds and exhibit superior high-temperature resistance compared to near-alpha titanium alloys. TiAl alloys are particularly heat-resistant, capable of operating at temperatures up to 725°C. These alloys are used in high-temperature components such as the low-pressure turbine rotor blades of the B-747 aircraft engine, significantly improving engine performance and efficiency.
From commercially pure titanium to titanium-aluminum alloys, a wide variety of titanium alloy grades are used in the aerospace field, each with its own unique properties and applications. With the continuous advancement of aerospace technology, the performance requirements for titanium alloys are also increasing. In the future, with advances in materials science and manufacturing technology, the variety and performance of titanium alloys will continue to expand and improve, providing even more solid material support for the development of aerospace equipment.
