Memory super alloy

They also contain low amounts of other metals such as Al, V Nb, Ta, Mn, Zr and/ or Sn. The only pure metals used for medical devices are Ti and Ta. The only binary alloys applied for biomaterials are Ti-base alloys, for example, Ti30Nb, Ti30Ta Ti(n)Mn, and memory super alloys NiTi (Bradley 1994 Breme 1994 Breme and Wadewitz 1989). 

Currently all commercial vena cava filters are fabricated from either nitinol (nickel and titanium alloy), phynox (nickel, cobalt, chromium, iron, and molybdenum alloy), or stainless steel wire in various catheter sheath sizes ranging from 7 to 14 French (2.3-4.7 mm diameter). These metals have been chosen because they are biostable and have low thrombogenicity. This means that blood is less likely to form clots on the surface, and cells are not encouraged to grow around the device. Moreover, nitinol is a thermal shape-memory and super-elastic alloy that is self-expanding after deployment. For this particular application the nitinol will be tuned to expand on exposure to body temperature." ... 

Above the transition temperature an extraordinary elasticity can be observed in the shape memory alloys. Figure 6.53 shows a uniaxial stress-strain diagram of a pseudo-elastic (or super-elastic) SMA. 

Metals share excellent mechanical and conductivity (electrical and thermal) properties ideal for high stress apphcations such as heart valves. Titanium—nickel alloys have become the most common material for metaUic cardiovascular applications (stents and valves) due to unique properties shape memory effect, super-elasticity, high degree of biocompatibility moreover, they are almost completely inert and nonmagnetic. 

Falvo A, Futgiuele FM, Maletta C (2005) Laser welding of a Nili alloy Mechanical and shape memory behavior. Materials Science and Engineering A. 412 235-240 Wu MH (2001) Fabrication of Nitinol materials and components. Proceedings of the international conference on shape memory and super-elastic technologies, Kunming, China, 285-292... 

---