Superelasticity and mechanical properties of TiNi thin wire after heat treatment

Alloys based on titanium nickelide are widely used in medicine as implants. Nichrome wire has gained particular popularity, it is used to manufacture mesh implants used in working ele-ments for orthodontic devices, artificial ligaments for tendon ruptures, etc. However, before man-ufacturing products from titanium nickelide wire, the latter is subjected to heat treatment to give the desired shape during the compression process. Many works are devoted to the study of an-nealing of wires more than 1 mm thick, so the purpose of this work will be to present the results of studying the structure and mechanical properties of titanium nickelide wires with a diameter of 100 μm, annealed at 300, 400, 500, 600 ℃. The deformation behavior of the wire was studied after tensile strength tests. The obtained tensile curves describe its mechanical properties and superelasticity. The fracture surface of the wire was examined on a scanning electron micro-scope with an energy-dispersive X-ray analyzer. Fractographic analysis of the main fracture characteristics was also performed. It was found that the tensile strength and martensitic shear stress decrease with increasing annealing temperature. The annealing conditions determined by the obtained results do not suppress the superelasticity of the wire, but impart strength and duc-tility necessary for medical purposes. Wire samples annealed at 300 and 400 °C demonstrate similar superelastic behavior in cyclic tests characterized by mechanical hysteresis and 1 % residual deformation. Annealing of 100 μm thick wire at 500 and 600 °C provoked greater resid-ual deformation after cyclic tests.