The most popular characteristics of nitinol are shape memory alloy and super elasticity in most of its application.
These two distinct properties have long defined the amazing features and versatility of Nitinol.
There are other properties that are quite unknown to most of us.
Stress hysteresis is considered as the rarest characteristic of Nitinol alloys.
Although stress is elevated in a linear way when pressure is applied for most engineering materials, Nitinol acts differently.
It exhibits a property called loading plateau.
This involves small elevation of stress despite large application of pressure.
In this process, stress is reduced fast enough until the unloading plateau is reached which is triggered by the unloading at the end point of its region.
In this area, the pressure is recovered with an insignificant amount of stress.
The constant opening force of stent moving against the vessel wall is permitted by nitinol's rare elastic hysteresis.
This shows the tendency of the opening force to stay low despite the significant deflections of the stent.
On the other hand, the forces created by the stent to withstand compression elevates rapidly with deflection until the unloading end is reached.
The stiffness of Nitinol stents which relies on temperature is another rare characteristic of this alloy.
As long as the stents are exposed on temperature above 30 degrees C, nitinol stents are observed to be much steeper than when it's exposed to temperature below 30 degrees.
In some experiments, it shows the increase in the chronic outward force when subject to temperature that ranges from 20 to 37 degrees C.
As one of the usual characteristics of Nitinol is its ability to revert back to its original shape, within its processing stage, the stent's temperature transition can be altered.
This allows second hand designer the flexibility of changing the amount of the stent's radial forces without altering the dimension which includes the design.
Carotid artery is a good example of the Nitinol's resistance feature which can be deformed by external pressure in superficial vessels.
This is far batter than balloon-expandable stents which have shown a potential risk of deformation in carotid arteries when external pressure is applied which then leads to clogged blood vessels once the maximum strength is reached.
Despite the ultimate strength that stainless steel stents can withstand, nitinol stents can withstand permanent deformation exerted by external pressure.
Full compressibility is shown by nitinol which has the ability to revert back to its original shape when the external pressure which deforms it is released.
It is found to be ferromagnetic with a reduced susceptibility to magnetic force as compared with stainless steel.
It has been observed that the stent can recover once the pressure is released.
Thus, it has been found to be biocompatible which means that it is fit for the human tissue to adapt.
That said; nitinol creates fewer artifacts as compared to stainless steel.
Nevertheless, take note that processing of the material can impact its quality significantly.
Biased stiffness is the term used to signify its path dependence or commonly known as stress hysteresis.
This means that nitinol shows a super elastic response to non linear force.
These properties have made nitinol a metal of choice in terms of medical applications.