Structure and Properties of Cold-Worked and Annealed Ti-Ni-Co Shape Memory Wires Designed for Medical Application

Abstract

The effect of plastic deformation by drawing and rolling in the martensite state and final annealing on the structure, grain size, martensitic transformations and shape memory properties of TiNiCo wires is described in the paper. The wires were cold worked by 30 and 40% and then annealed at the temperature range 300-600oC. The structure, phase composition and transformation behaviour of samples after processing and annealing were studied using transmission electron microscopy (TEM), X-ray diffraction (XRD) method and differential scanning calorimetry (DSC) technique. The marformed and annealed at 400 and 450oC wires exhibited a very good superelastic behaviour. The obtained wires were used for production of the shape memory staples with the recovery temperatures close to the human body temperature and as well as for small superelastic staples for fixation of mandible bone fractures.

Archives of Metallurgy and Materials

“…Mixing enthalpy (ΔH mix ) for HEAs should be in -15÷5 kJ/mol range [16][17]. Electronegativity differences parameter -Δχ is correlated with elemental segregation in alloys [11] and the formation of topologically close-packed (TCP) phases. For high entropy materials electronegativity should be in the range from -15 to 5 eV [18][19][20].…”

“…Ni and Ti were chosen as main elements for formation of Nitinol shape memory alloys [10]. The alloy additions such as Ta, Co and Cu also show a shape memory effect in various shape memory alloys [11][12][13]. High entropy alloys exhibiting shape memory effect are new group of high entropy materials and alloys of similar chemical composition have not been reported in the literature yet.…”

Low-Temperature XRD Study of Phase Transformations in NiTi and TiNiCo Shape Memory Alloys Used for the Preparation of the Prototypes of Medical Implants

“…These kinds of staples are applied in the fixation of the mandible and face bone fractures and implants in cranioplasty [2,3]. Phase transformations in the wires of the studied alloys after various thermo-mechanical and thermal treatments have been defined by the differential scanning calorimetry (DSC) method and three-point bending and free recovery ASTM F2082-06 tests [4,5]. The X-ray diffractometry with temperature chambers have been successfully applied in investigations of NiTi phase transformations [5][6][7].…”