Nickel titanium

Nickel Titanium (NiTi) is a shape memory alloy also commonly referred to by its trade name, Nitinol. Above its transformation temperature, Nitinol is superelastic, able to withstand a large amount of deformation when a load is applied and return to its original shape when the load is removed. Below its transformation temperature, it displays the shape memory effect. When it is deformed it will remain in that shape until heated above its transformation temperature, at which time it will return to its original shape. Buehler discovered this along with Wang.

Nitinol is typically composed of approximately 55% Nickel by weight. Making small changes in the composition, can change the transition temperature of the alloy significantly. For this reason, Nitinol may or may not be superelastic at room temperature. These unique properties and tailorability of Nitinol to be used in a wide range of temperatures makes it suitable for many applications, particularly in medicine.

Applications

In dentistry, the material is used in orthodontics (for brackets and wires) and in endodontics, where Nitinol files are used to clean and shape the root canals during the root canal procedure.

Another significant application of Nitinol in medicine is in stents. A collapsed stent can be inserted into a vein and heated (returning to its original expanded shape) helping to improve blood flow.

Nitinol is also popular in extremely resilient glasses frames.

Potential future applications include:
• Artificial muscles
• Earthquake resistant and self-repairing buildings

See Also

Shape memory alloy
Ferroelasticity
Superelasticity