Nitinol that is superelastic can be stretched up to 30% of the way without permanently changing shape. Nitinol Superelastic Spring extraordinary yield and intense yield strength are two highly unique characteristics that can be linked to the fact that it is not a typical alloy. It is an intermetallic, which is an alloy with a highly organized interatomic structure and a very accurate nickel-to-titanium ratio. Fishing wire is another name for this substance.
The composition is quite similar to our shape memory alloys, but this material doesn't have a memory effect and won't change shape when heated. Use the aforementioned source to find a wire that takes on a new shape when heated.
If you plan to utilize superelastic nitinol in a very cold environment, we advise testing a sample first to see how it responds because it technically exhibits a very small memory effect with a transition phase at about -10oC.
Characteristics
The wire is a dark grey, glossy titanium tone with a surface oxide tinge. The inner core is nickel white when it has just been sliced. Since nitinol is extremely resistant to abrasion and has self-healing qualities, cutting and kinking the wire is difficult. It is non-toxic and does not require special handling or protection from oxidation or moisture.
At temperatures above room temperature, superelastic nitinol is stiff and springy, like spring steel or piano wire. It shares mechanical traits with shape memory NiTi with a reduced transition phase, like our 15oC SMA, but lacks the memory effect.
Qualities that Make for Good Medical Applications
- Nitinol is primarily used in stents, although there are several other uses as well, some of which will be briefly discussed here.
- Nitinol is very adaptable in applications that employ high temperatures to activate a device (called thermal deployment), such as the Simon Nitinol® vena cava filter, because of the shape memory effect.
- In devices like stone retrieval baskets, superelastic nitinol also elastically attains a free shape after being removed from a restricting device like a cannula (called elastic deployment).
- Catheters are guided into the body's hard-to-reach spaces using nitinol guidewires.
- They are advantageous because, unlike stainless steel, they may kink without breaking. Since the wire is elastic, it can move through the body in any direction without suffering any harm. Nitinol will provide torque and rotate smoothly.
- Nitinol tubes are utilized as biopsy needles, stent delivery systems, catheter shafts, and workability for medicines, stents, and guidewires. Nitinol's superelastic hysteresis, sometimes known as the "flag" of a stress-strain diagram, is advantageous for stent performance.
