Equiatomic nickel-titanium alloy

For instance, equiatomic nickel-titanium alloy (nitinol) is a very attractive material for biomedical applications. However, the high nickel content of the alloy and its potential influence on biocompatibility is an issue for nitinol-composed devices. Corrosion resistance of nitinol components from implantable medical devices should be assessed according to regulatory processes and standard recommendations. It is now well known that nitinol requires controlled processes to achieve optimal good life and ensure a passive surface, predominantly composed of titanium oxide, that protects the base material from general corrosion. Passivity may be enhanced by modifying the thickness, topography, and chemical composition of the surface by selective treatments [46]. 

Shape memory alloys were the first SMMs studied. Chang and Read (1951) developed the first shape memory alloy, composed from gold and cadmium. However, only after 1963, when an equiatomic nickel-titanium alloy called Nitinol was developed (Buehler et al., 1963), were shape memory... 

The most noteworthy and extensively researched shape-memory materials are shape-memory alloys (SMAs). Olander first discovered and reported in 1932 a novel metallic transformation of gold-cadmium (AuCd) alloy, whose pseudoelasticity triggered imusual macroscopic deformation [12]. The discovery of the SME in equiatomic nickel-titanium (NiTi) alloy, which is well known as nitinol, represented a paradigm shift in the SMA field. 

The titanium-nickel alloys show unusual properties, that is, after it is deformed the material can snap back to its previous shape following heating of the material. This phenomenon is called shape memory effect (SME). The SME of TiNi alloy was first observed by Buehler and Wiley at the U.S. Naval Ordnance Laboratory [Buehler et al, 1963]. The equiatomic TiNi or NiTi alloy (Nitinol) exhibits an exceptional SME near room temperature if it is plasticaUy deformed below the transformation temperature, it reverts back to its original shape as the temperature is raised. The SME can be generally related to a diffusionless martensitic phase transformation which is also thermoelastic in nature, the thermoelasticity being attributed to the ordering in the parent and martensitic phases [Wayman and Shimizu, 1972]. Another unusual... 

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