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Nitinol is actually an acronym: NiTiNOL, which stands for Nickel Titanium Naval Ordinance Laboratory a name that harkens back to its discovery in 1962. Since that time, the world has been developing uses for this incredible material. It's most commercially recognized application is in orthodontic braces but the medical device industry has been finding more and more uses for this material.
Setting Nitinol apart from other metals are it's super elastic and shape memory properties. The material can withstand as much as an 8% strain and still recover to its original shape, which is about 16X greater than stainless steel, which typically can only withstand .5%, strain before plastic deformation occurs.
The medical industry refers to two types of Nitinol: Superelastic and Shape Memory. Technically both are shape memory and the differentiation people refer to is
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the temperature at which a complex cubic lattice structure of nickel and titanium convert from Austenite to Martensite, a process called Martensitic transformation. In layman's terms, Superelastic nitinol is superelastic at or around 0°C such that the material remains superelastic at room temperature.
Shape Memory Nitinol is typically Nitinol, which transforms at body temperature and is most commonly used in minimally invasive catheter procedures such as arterial stents. The martensitic transformation may be reversed by cooling the metal below its martensitic phase, which is separate from its Austenitic phase curve, in other words, cooler than the temperature at which it became superelastic. While in its cooler austenitic phase, the metal behaves more like solder and is easily deformed. However, once
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