During the late 1940s and early 1950s, as World War II was winding down, scientists began to explore the unique properties of titanium, leading to the development of large-scale titanium sponge production. The United States took the lead, establishing high-capacity plants at TIMET in 1951 and RMI in 1958. In Europe, the UK launched similar initiatives with Deeside Titanium in 1951, while France began producing titanium sponge by 1963. Meanwhile, Japan's Osaka and Toho Titanium achieved significant progress in research and productivity by 1954. The Soviet Union followed suit in 1954, rapidly scaling up its production and eventually surpassing the U.S. as the world's largest producer by 1979.
Titanium alloys, prized for their superior strength-to-weight ratio, high corrosion resistance, and thermal stability, have since become essential in aerospace engineering. These materials replaced traditional metals like steel and aluminum in weight-sensitive and high-temperature applications such as jet engines, landing gear, and structural airframes.
α alloys are primarily used in environments requiring excellent corrosion resistance, high fracture toughness, and the ability to perform in moderately high temperatures. Commercially pure titanium alloys in their annealed form are commonly used in aerospace for non-critical tasks such as in galleries and laboratories. Ti-3Al-2.5V (Ti-3–2.5) is employed in high-pressure hydraulic lines as a lightweight alternative to steel tubes, reducing weight by up to 40%. This alloy is also used for manufacturing honeycomb cores, which require higher strength than commercially pure titanium.
In cryogenic industries, Ti-5Al-2.5Sn (Ti-5–2.5) stands out for its high fracture toughness and ductility, making it a key material in space shuttle applications. Ti-8Al-1Mo-1V (Ti-8–1–1) is widely used in military jet engines, especially for fan blades, due to its high strength and durability. IMI 829, a specialized α alloy, performs effectively up to 540°C in the β-solution aged condition and is used in compressor discs, spacers, and blades of the RB211-535E4 engine in Boeing aircraft. For even higher temperature requirements, IMI 834 is preferred, operating at temperatures up to 600°C, especially in the Rolls-Royce Trent 800 engine's compressor discs. Timetal-1100, an advanced version of Ti-6–2–4–2S, is suitable for temperatures up to 600°C and is commonly used in Allison gas turbine engines for its strength and high-temperature resilience.
The α+β alloys combine the advantages of α-phase stability with the high strength of β-phase constituents, making them versatile for structural and rotating components in aerospace. Ti-6Al-4V (Ti-6–4) is the most widely used titanium alloy in aerospace, employed in both rotary and static components, as well as in structural elements like nacelles, fuselage, wings, landing gear, and gas turbine floor support structures. Ti-6Al-6V-2Sn (Ti-6–6–2) offers superior strength and corrosion resistance compared to Ti-6–4 and was extensively used in the Boeing 747's landing gear system, as well as in components like drag braces and torsion chains.
Ti-6Al-2Sn-2Zr-2Mo-2Cr+Si (Ti-6–22–22), developed in the early 1970s, is highly valued for its strength and damage durability, making it ideal for the F-22 fighter jet. Ti-6Al-2Sn-4Zr-6Mo (Ti-6–2–4–6), while performing well at moderate temperatures (up to 315°C), is used in military engines such as the F-119 and F-100, though its lower damage resistance limits its commercial adoption. Ti-5Al-2Sn-2Zr-4Mo-4Cr is another α+β alloy designed for fan and compressor discs, withstanding temperatures up to 400°C and excelling in fracture toughness and crack propagation resistance, making it ideal for damage-tolerant designs in commercial aircraft engines.
β alloys are highly sought after in aerospace applications where high strength, excellent fracture toughness, and weight reduction are critical. Ti-13V-11Cr-3Al (Ti-13–11–3) was widely used in the SR-71 Blackbird for structural components like wing and body covers, frames, longerons, bulkheads, ribs, rivets, and landing gear. Ti-15V-3Cr-3Sn-3Al (Ti-15–3) is often found in strip form, used for applications such as flat product springs, including clock springs.
In modern aircraft, Ti-10V-2Fe-3Al (Ti-10–2–3) is used in the main landing gear of the Boeing 777, reducing weight by 270 kg and eliminating stress corrosion concerns. This alloy is also employed in rotor systems by companies such as Westland, Bell, Sikorsky, and Eurocopter. Timetal 21S (Ti-15Mo-3Nb-3Al-0.2Si) operates at temperatures between 480–565°C and is used in engine components for the Boeing 777, such as nozzles, plugs, and aft cowls. This material contributes to significant weight savings of up to 75 kg per aircraft, while maintaining high-performance standards.
The application of titanium alloys in aerospace is driven by their unique properties, tailored to meet specific operational demands. α alloys excel in high-temperature and cryogenic environments, offering toughness and corrosion resistance. α+β alloys provide a balance of strength, ductility, and versatility, making them indispensable for structural and dynamic components. β alloys, with their superior strength and fracture toughness, enable significant weight savings and are crucial for critical, high-performance systems. Together, these alloys represent the backbone of modern aerospace engineering, enabling advancements in efficiency, safety, and sustainability.
Najafizadeh, M., Yazdi, S., Bozorg, M., Ghasempour-Mouziraji, M., Hosseinzadeh, M., Zarrabian, M., & Cavaliere, P. (2024). Classification and applications of titanium and its alloys: A review. Journal of Alloys and Compounds Communications, 100019.