Nitinol is a metal alloy sometimes called a shape memory alloy (SMA).
Nitinol has two closely related and unique properties: shape memory and superelasticity. Shape memory is the ability of a material to deform at one temperature and then return to its original shape when heated above its “transition temperature.” Superelasticity occurs in a narrow temperature range just above the transition temperature; under these conditions, the pre-deformed shape returns without heating.
Shape memory alloys (SMAs) are considered to be one of the most promising smart materials. They can provide novel solutions in various fields for various applications such as actuators, biomedical applications, clamping systems, etc. Among the commercially available shape memory alloys, nickel titanium SMA stands out for its excellent performance and reliability. In addition to its strain recovery capabilities, Nitinol is also attractive for medical applications because of its biocompatibility, corrosion resistance, and fatigue properties.
Shape Memory Alloy Type
Type | Description |
Two-way Shape Memory | Alloy that restores high-temperature shape when heated, and restores low-temperature shape when cooled |
One-way Shape Memory | Alloy deforms at sub-transformation temperatures and restores pre-deformation shape when heated, demonstrating unidirectional memory behavior. |
Glossary
Shape Memory Effect
“Shape Memory” describes the restoration of the original shape of a plastically deformed sample upon heating.
Superelastic Effect
An elastic (reversible) responses to an applied temperature, caused by a phase transformation between the austenitic and martensitic phases of a crystal.
Ms– Initial temperature for an austenite to martensite transition
Mf– Final temperature for an austenite to martensite transition
As– Initial temperature for a martensite to austenite transition
Af– Final temperature for a martensite to austenite transition
