Rationale for titanium usage in the aerospace industry

[AirborneMetals]

Titanium, having atomic number 22, is classified as a transition metal. In its natural state it already possesses some characteristics making it an interesting material for certain aerospace applications.

These are:

Strength
It possesses roughly the same strength as steel; however it is much lighter. In other words: it has a very favorable strength-to-weight ratio, which is an important parameter in aerospace.

Favorable fatigue properties
Equally important is its high resistance to fatigue. Many aerospace structures are fatigue-critical due to cyclic loading, requiring fatigue-resistant materials.

Corrosion resistance
Outstanding corrosion resistance properties lead to applications in harsh environments; for example it is used in propellor shafts. Also, this is part of the justification for use of titanium within landing gear of newer wide body aircraft.

Resistance to extreme temperatures
The material is resistant to both very high and cryogenic temperatures, temperature fluctuations, and extreme environments in general. Furthermore, it has a low coefficient of thermal expansion, which makes it compatible with other materials like carbon fiber composites.

Machinability
The material can be machined, but this poses challenges (when compared to aluminium it is much harder to machine). For example, the poor heat dissipation causes concentration of heat on the cutting edge and the tool face.

Creep resistance
Creep resistance (the ability to withstand deformation under sustained load and / or elevated temperatures) is another favorable characteristic.

Toughness
The material is very tough, meaning to say it can absorb large amounts of energy per unit volume before rupturing. It can also retard crack growth relative to other aerospace materials, such as aluminium.

Above-mentioned properties are greatly alloy-dependent and can be further enhanced and fine-tuned by processes like heat treatments.