Yasenchuk Yu. F.; Artyukhova N. V.; Chekalkin T. L; Anikeev S. G.; Kim Ji-Soon; Kang Ji-Hoon; Gunther V. E
Abstract
Modern medical technologies have developed many new devices that can be implanted into humans to repair, assist or take the place of diseased or defective bones, arteries and even organs. The materials, especially porous ones, used for these devices have evolved steadily over the past twenty years with ...
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Modern medical technologies have developed many new devices that can be implanted into humans to repair, assist or take the place of diseased or defective bones, arteries and even organs. The materials, especially porous ones, used for these devices have evolved steadily over the past twenty years with TiNi-based alloys replacing stainless steels and titanium. The aim of the paper is to presents results for examination of porous TiNiMoCo-based alloy intended further to be used in clinical practice. Porous TiNi-based alloys showing shape memory effect were obtained by the methods of reaction and diffusion sintering with cobalt additives. From the results of the analysis of temperature dependences determined by the measurement of electrical resistivity and shape memory effect test, the effect of cobalt addition on the martensitic transformations in sintered body is described. The addition of cobalt during reaction and, especially, diffusion sintering, results in a decrease in the internal stresses in the TiNi phase. The addition of Co more than 1 at. % led to precipitation hardening of the alloy. Cobalt at concentrations studied in the work led to suppression of martensitic phase transformation.
Victor E. Gunther; Timofey L. Chekalkin; Ji-Soon Kim; Valentina N. Hodorenko
Abstract
The brief overview of published articles on Nitinol studies reflects, in fact, a little misunderstanding of a thermodynamic importance since there is no whole concept or paradigm considering the martensite transition and related effects in terms of thermodynamic arguments. TiNi-based alloys are basically ...
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The brief overview of published articles on Nitinol studies reflects, in fact, a little misunderstanding of a thermodynamic importance since there is no whole concept or paradigm considering the martensite transition and related effects in terms of thermodynamic arguments. TiNi-based alloys are basically functional materials. They’re more important for what they do than for what they are. In order to make it easier to understand complicated behavior of TiNi-based alloys under general and special conditions, a new approach is introduced. This work was aimed at studying the hysteretic behavior of TiNi-based alloys. Mechanism of hysteretic phenomenon in TiNi-based alloys showing shape memory effect, superelasticity and ferroelasticity has been considered. Hysteretic behavior in repeatable shape memory effect was thermodynamically analyzed with the aid of Helmholtz potential formalism. Correlation of deformation, temperature and latent heat of phase transition under the constant load was established. Maximum hysteresis width achieves when the product ??? during phase transition tends to ?H, and when the product ??? tends to zero the value of ?T approximates the difference (As – Mf) or (Af – Ms).