Titanium Applications: A Game Changer in Aerospace, Automotive, and Medical Fields

Titanium's exceptional properties such as its high strength, low density, and resistance to corrosion have made it a valuable material since its discovery. Its use began to gain significant momentum during World War II, with large-scale production taking off in the USA and Europe in the 1950s. Soon after, Japan and the Soviet Union expanded their production capabilities. Today, the most widely used titanium alloy is Ti-6Al-4V, accounting for more than 50% of the market. While over 100 titanium alloys have been developed, only 20 to 30 have achieved commercial relevance. Among them, titanium aluminides, particularly TiAl-based alloys, are seeing increased use in both the aerospace and automotive industries due to their unique high-temperature properties.

Titanium in Aerospace Applications

Titanium is widely used in the aerospace industry due to its high strength-to-weight ratio, corrosion resistance, and ability to withstand extreme temperatures. In the USA, 70-80% of all titanium is used in aerospace, particularly in engine and airframe systems. Titanium alloys are preferred over aluminum and steel because they provide significant weight savings, space optimization, and higher temperature resistance.

• CP-Ti (Commercially Pure Titanium): Used for floor support structures in high-corrosion areas like kitchens and lavatories, as well as pipes and clips in environmental control systems.
• Ti-3Al-2.5V: Replaces stainless steel in high-pressure hydraulic lines, offering 40% weight savings, and is also used in cryogenic applications.
• Ti-6Al-4V: Extensively used for fan blades in military engines and for structural components like fuselages, landing gears, and wings.
• Ti-10-2-3: Used in Boeing 777 landing gear and rotor systems of helicopters, resulting in significant weight savings and reducing stress corrosion cracking risks.

Titanium in the Automotive Industry

Titanium began revolutionizing the automotive industry with Formula 1 racing cars in the 1980s, where weight savings were paramount. Today, the metal is commonly used in components like exhaust valves, connecting rods, and retainers. The lightweight yet strong nature of titanium helps reduce the overall vehicle weight, improving fuel efficiency and performance.

Key Applications of Titanium in the Automotive Industry:

1. Engine Components:
   • Intake Valves: Often made from Ti-6Al-4V alloy, titanium intake valves are used in many cars and motorcycles due to their high strength and ability to withstand high temperatures.
   • Exhaust Valves: For exhaust valves, which are exposed to high temperatures, alloys such as Ti-6Al-2Sn-4Zr-2Mo-0.1Si (6242S) and TIMETAL® 1100 (Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si) are used for their superior heat resistance.
   • Turbocharger Rotors: TiAl (Titanium-Aluminum) alloys are used in turbocharger rotors for their high strength and temperature resistance.
   • Connecting Rods: Made from Ti-6Al-4V, these components benefit from titanium's high strength-to-weight ratio.
2. Suspension and Frame:
   • Suspension Springs: Ti-6Al-4V and Ti-6.8Mo-4.5Fe-1.5Al alloys are used for suspension springs due to their high strength and lightweight properties.
   • Frame Structures: Titanium alloys are used in frame structures for their durability and weight-saving characteristics.
3. Body and Armor:
   • Body Panels: CP-Ti (Grade 4) and Ti-6Al-4V are used in certain high-performance and specialized vehicles for body panels due to their excellent strength and corrosion resistance.
   • Armor: Ti-6Al-4V is used in automotive armor applications for its high strength and protective qualities.

Challenges and Developments:

• Surface Treatments: One challenge with titanium alloys, particularly in engine applications, is their wear resistance. Various surface treatments, such as TiN coatings, Mo thermal spray coatings, and Cr plating, have been used to improve durability. However, these treatments can be expensive and may not provide long-term wear resistance. Recent developments include oxidizing treatments that enhance hardness by forming a thick hardened layer on the titanium surface.
• New Alloys: Research is ongoing to develop new titanium alloys for automotive applications, such as Supr-TIX, Super-TIX51AF, Super-TIX800, and TIMETAL® LCB. These new alloys aim to provide better performance, lower costs, and improved properties for various automotive parts.

Titanium’s Role in Biomedical Applications

Titanium alloys have become critical materials in the development of medical devices, starting from the 1970s due to their advantageous properties. These materials, particularly commercially pure titanium (CP-Ti) and Ti-6Al-4V, offer exceptional biocompatibility, a high strength-to-weight ratio, reduced elastic modulus, and superior corrosion resistance when compared to other metals like stainless steel or cobalt-chromium alloys.

Properties of Titanium Alloys in Medical Devices:

• Biocompatibility: CP-Ti is considered one of the best biocompatible metals because of its ability to form a stable, inert oxide layer, making it highly suitable for implants.
• Mechanical Strength: Titanium alloys like Ti-6Al-4V possess a tensile strength between 900 to 1200 MPa, which makes them strong enough for various medical applications, including implants.
• Corrosion Resistance: Their resistance to corrosion in the human body is vital, as implants are subjected to a harsh internal environment.
• Elastic Modulus: The elastic modulus of titanium alloys, however, is higher than bone, which can lead to challenges in orthopedic applications, such as inadequate load transfer from the implant to adjacent bone. This often necessitates surface treatments or coatings for better wear resistance.

Applications of Titanium Alloys:

1. Orthopedic Implants: Ti-6Al-4V is commonly used in hip and knee prostheses and trauma fixation devices like screws, nails, and plates. However, its relatively high elastic modulus compared to cortical bone (110 GPa vs. 18 GPa) poses some limitations for these applications.
2. Dental Implants: Titanium alloys, including CP-Ti and Ti-Mo-Zr systems, are widely used for dental implants due to their biocompatibility.
3. Cardiac Devices: Titanium is also employed in cardiac applications, such as heart valves, pacemakers, and artificial heart components.
4. Emerging Alloys: Ti-6Al-4V is being replaced in some applications by newer titanium alloys free of vanadium and aluminum, such as Ti-6Al-7Nb and Ti-5Al-2.5Fe, due to concerns about the toxicity of V and Al. Newer alloys with elements like niobium (Nb), tantalum (Ta), and zirconium (Zr) aim to provide better biocompatibility and fatigue strength.

Challenges:

• Wear Resistance: Titanium alloys like Ti-6Al-4V suffer from poor wear resistance, making them unsuitable for bearing surfaces in joints without additional treatments.
• Toxicity of Alloying Elements: The presence of vanadium and aluminum in some titanium alloys has raised concerns about their toxicity. Hence, there is a growing interest in developing vanadium- and aluminum-free alloys.
• Elastic Modulus Matching: The high elastic modulus of some titanium alloys compared to bone remains a challenge, leading to the development of newer alloys that more closely match the mechanical properties of bone to avoid implant failure.

Conclusion

At Quest Alloys and Metals, we are committed to not only celebrating titanium’s remarkable properties but also recovering and refining this valuable material from aerospace components. By reclaiming titanium from decommissioned aircraft, we ensure that this high-value metal is recycled for use in aerospace, automotive, medical, and other industries. This sustainable approach not only reduces waste but also supports innovation in these vital sectors.

In a world that increasingly values both performance and environmental responsibility, titanium and our role in refining it ensures that industries continue to thrive with materials that meet the highest standards. Whether it's improving the efficiency of a jet engine or saving a life with a titanium implant, Quest Alloys is proud to be part of the process that fuels the future.

Veiga, C., Davim, J. P., & Loureiro, A. J. R. (2012). Properties and applications of titanium alloys: a brief review. Rev. Adv. Mater. Sci, 32(2), 133-148.