Shape Memory Alloys for Biomedical Applications

Fatigue and fracture of wires and cables for biomedical applications

“…159 An overview of SE and SM systems are provided herein with additional details given elsewhere. 28,102,155,[160][161][162][163][164][165] Nitinol's unique properties are due to the solid-solidphase transformation between austenite and martensite and defined by four different transformation temperatures: A s , A f , M s and M f , which are the austenite start, austenite finish, martensite start and martensite finish, respectively. 160 The SE condition presents a high-temperature B2 (Strukturbericht) or 221 (International Tables for Crystallography, space group Pm-3m) austenitic crystal structure with Ni-rich precipitates and is a thermodynamically metastable structure.…”

“…102,155,162,164 The austenitic structure will transform to a stress-induced martensite (SIM) when stressed at a temperature greater than the A f and will subsequently return to the austenitic (parent phase) upon unloading. 163 The A f value is defined as the transformation of the last volume of martensite into austenite of a stress-free sample upon heating. 102 This value can be experimentally determined via differential scanning calorimetry (DSC) in addition to the M s , M f and A s .…”

<i>In-Situ</i> Synchrotron High Energy X-Ray Diffraction Study of Micro-Mechanical Behaviour of R Phase Reorientation in Nanocrystalline NiTi Alloy

“…NiTi shape memory alloys (SMAs), owing to their unique shape memory effect, superelasticity [1], good biocompatibility [2] and high corrosion resistance [3], have been used in many applications in aerospace and automobile industries, in consumer goods and in medical technology, as fasteners, actuators, stents, and medical guidewires, to name a few [4][5][6][7][8]. The unique shape memory properties are due to the martensitic transformations in these alloys.…”

Transformation Volume Effects on Shape Memory Alloys

“…The Ti-Ni alloy system will be chosen as the illustrative example. The properties of Ti-Ni alloys deserve a consideration because of the broad use of these alloys in the medicine [6] and engineering [4,5,7].…”

“…Because of their physical equivalence, the domains of martensitic phase (martensite variants) are separated by the coherent, and therefore mobile, interfaces. The shear character of MT strains and appearance/presence of mobile interfaces give rise to a complicate thermoelastic behavior of the shape memory alloys and their engineering and medical applications [3][4][5][6][7]. The most of these applications are based on the shape memory effect and accessibility of large strain values under the moderate mechanical loading.…”