Применение сплава из никелида титана в офтальмохирургии

Alloys based on titanium nickelides have high mechanical properties, as well as a set of special properties: shape memory effect, superelasticity, high level of damping and corrosion resistance, biocompatibility. To obtain titanium nickelides, various technologies are used: smelting in arc and induction vacuum furnaces, electrolysis of molten media, sintering, selfpropagating high-temperature synthesis, which are distinguished by high energy consumption of processes and significant cost. To reduce the cost of obtaining alloys based on titanium nickelide, a technology of double-arc melting in argon using electrode wires made of titanium and nickel was proposed, which makes it possible to obtain not only blanks and parts of the required shape from these alloys, but also deposited layers on the surface of finished products. The conducted studies of processes of titanium nickelides formation by double-arc melting showed that the chemical composition of samples is determined by modes of electric arc melting of electrode wires and, first of all, by the ratio of the feed rates of nickel and titanium wires. The nickel content in obtained samples varied within 34.1–60.1%. The structure of the samples was determined by the ratio of feed rates of electrode wires and was represented by phases: α(Ti); NiTi2; NiTi. The structure based on NiTi2 and Ti is formed when the ratio of the nickel wire feed rate to thetitanium wire feed rate is equal to 0.38. With the feed rate ratio in the range of 0.44–0.86, the structure of samples is represented by phases NiTi2 + NiTi. A single-phase structure based on titanium nickelide (NiTi) during double-arc melting in an argon atmosphere is formed at the feed rate ratio of the order of 1–1.14 of nickel and titanium wires with the same diameter.

Alloys with the shape memory effect based on titanium nickelide are well known and used quite widely in medicine, aircraft and spacecraft engineering, and other fields of mschine building. These alloys are used in creating thermomechanical parts of structures, temperature-sensitive gauges, and thermoregulators. Titanium alloys with the shape memory effect that posses high damping properties are used when vibrations and noise have to be limited in order to provide effective operation of machine parts and engineering systems as a whole. Commercial titanium-base alloys have lower characteristics of shape regeneration than alloys based on titanium nickelide. However, commercial alloys are much less expensive and are used to produce a wide range of semifinished products. In these materials the characteristics of shape regeneration and damping are often determined by the mechanism of change of shape in deformation, which has not yet been studied appropriately. The present work is devoted to the mechanisms of inelasticity in titanium alloys in various stages of the action of the shape memory effect.

In the article there is presented a brief overview of combined systematic investigations of the alloys exhibiting thermoelastic martensitic transformations (TMTs). As is known, such alloys are distinguished by a whole number of specific one-and multi-fold-reversibility shape-memory (SM) effects occurring upon changing temperature, pressure, magnetic field, at the background of superplasticity and highly reversible deformation of transformation under a load or its relieving.There have been considered the alloys classification, the thermodynamical and kinetic aspects of TMTs, the origin and structural mechanisms of realization of multivarious pre-transition phenomena and TMTs proper, the influence of complex alloying, the peculiar features of a structure, the physico-mechanical properties and methods of production of the alloys most promising from the viewpoint of application. For this purpose there were employed structural methods of the X-ray diffraction (XRD) structure-phase analysis, neutron diffraction analysis, transmission and scanning electron microscopy techniques of high resolution, together with studying texture and atomic composition, as well as measuring a number of physical properties and SM-effect characteristics.The effect of the alloying and external actions of different origin on the magnetic and structural phase transformations and properties of the studied alloys with the magnetically, thermally, and mechanically controlled manifestations of the shape memory is discussed. A sequence of the TMTs with the formation of different martensitic phases, as well as the crystallographic structure and crystal-geometry specific features of the formation of these phases is described. The phase diagrams of the magnetic and martensitic transformations in a number of binary, ternary, and quaternary alloys synthesized via different schemes of alloying are presented.On the example of the binary and doped alloys TiNi it has been shown that an employment of thermo-mechanical treatments of the alloys via multiple or repeated torsion under pressure, rolling or drawing leads to their high-level strengthening and grain refinement (up to amorphization). In this case the use of low-temperature annealing provides for both the creation in the alloys of the homogeneous nanostructured state with a controllable grain size already in the interval of 50–200 nm and efficient regulation of physico-mechanical properties with retaining comparably high values of the parameters of SM, including deformation-, temperature-, and force-related.There has been revealed the effect of the grain size on the critical temperatures of TMTs and, as a consequence, on the TMT-stipulated SMEs. On this basement, in dependence of the grain size, the poly-packet, mono-packet twinned or single-crystal structures of martensite can be realized.There are discussed an experimentally revealed deformation-induced atomic disordering in Heusler alloys with self-forming a nanocrystalline fcc (A1) structure and amorphization in the alloys of titanium nickelide, as well as long-range order recovery in them taking place in the course of low-temperature annealing in conditions of retaining of the nanostructured state of austenite and at feasibility of cascade occurrence of TMTs and SMEs. It has been shown that the use of super-rapid quenching (SRQ) via employment of a melt spinning technique makes it possible to produce ductile submicrocrystalline ribbons of the Heusler Ni2MnGa-based alloys with magnetically controllable TMTs. For a number of alloys based on titanium nickelide the effect of SRQ on the internal structure, grain refinement, and amorphization has been considered. The reasons of the amorphization and ways of subsequent nanostructurization of the alloys under investigation are discussed.

—The influence of annealing at 600°C on the mechanical and thermomechanical characteristics of a Ti 50 Pd 30 Ni 20  alloy with high-temperature shape memory effect (SME) is studied. The best strength (σ u  = 1030 ± 140 MPa) and plastic ( ε 0 max "> ε ε 0 max  = 11.5 ± 6.0%, δ res  = 6 ± 4%) characteristics have been obtained after annealing at 600°C. The maximum thermally recoverable strain (ε SME  = 4.3%) and the maximum degree of shape recovery (η SME  = 67%) are achieved after annealing at 600°C after preliminary induced tensile deformation at temperatures  t d  =235–230°C and a strain rate  ε ˙ "> ε ε ˙  ≈ 2.8 × 10 –3  s –1 ; in this case, the reverse martensitic transformation temperatures characterizing the main shape recovery are  A sSME  = 220°C and  A fSME  = 249°C. Taking into account the studies carried out before, we found that the martensitic transformation temperatures increase almost linearly and, conversely, the SME and the degrees of shape recovery decrease as the titanium nickelide is alloyed with palladium in the content range from 30 to 50 at %. Linear regression equations are derived. The results obtained are used for designing safety devices of, e.g., crosscutting and pushing types.

In the era of modern personalized medicine, the problem of implant biocompatibility is acute. This problem is caused by a high risk of rejection, the appearance of various inflammations or other complications. This problem can be solved by modifying the surface of porous inorganic substances that are used in the quality of implants with macrocyclic compounds - cucurbit[n]urils. These compounds may contain medicinal or bioactive substances, which in turn can increase biocompatibility and slowly release the drug into the body, thereby helping to solve problems of rejection or complications. Porous titanium nickelide was used as a substrate - which is currently widely used in the field of bone tissue replacement and regeneration. This alloy has a number of unique properties that are absent from other materials, for example, the shape memory effect, superelasticity, bioinertness and bioactivity. In this work, we obtained materials by various methods (physical and chemical) based on porous titanium nickelide and cucurbit[ 6]uryl and investigated using SEM and TGA. Two physical methods were used to apply cucurbit[6]uril – immersion in solution and using ultrasound. In addition, the macrocyclic compound was produced in two different states - in the form of dispersion and in completely dissolved form. The results of the SEM show that the method of immersion in a dispersion solution covers the surface of titanium nickelide more А.Э. Ухов, В.А. Лариков, Г.А. Байгонакова и др. 154 tightly when, as in dissolved form, cucurbit[6]uril penetrates better into the pores. Cucurbite[6]uril is formed on the surface of titanium nickelide in the form of needle formations that are evenly distributed over the surface in the case of the immersion method in solution. Samples obtained using ultrasound have a lower distribution density, but in turn the formation of large conglomerates of molecules is prevented. The results of the study highlight the potential of using CB[6] to produce composite materials, especially when applied to porous substrates such as titanium nickelide.

Mechanical response of mesoporous amorphous NiTi alloy to external deformations

Titanium nickelide (nitinol) is one of prospective materials for production of special endo-prostheses and other parts and characterized with effect of shape memory. A specific feature of vascular endo-prostheses is the necessity to provide the required rigidity within the temperature interval from 15 to 42 оС. It has been established that titanium nickelide is able to provide the required rigidity but it depends on preliminary heat treatment parameters. So, it is important to determine rela-tions between rigidity of titanium nickelide wire and its preliminary heat treatment parameters for the given temperature in-terval. The aim of the work is to create devices that allow to estimate radial and flexural rigidity of elements made of flexible nitinol wire for manufacturing various medical products, including endo-prostheses of vessels – stents and stent grafts, filter traps. Laboratory digital scales and a specially developed dynamometer based on a cylindrical slotted spring and inductive displacement transducer have been used for measuring a load. The paper proposes possible variants of device designs used to monitor radial rigidity of blood vessel endo-prostheses, as well as to control flexural rigidity of endo-prosthesis elements and wire for their manufacture. The developed devices allow us to evaluate mechanical characteristics of samples under the desired temperature conditions. An introduction of the developed devices has permitted to carry out an operative control on radial and flexural stiffness of intravascular endo-prostheses elements both under conditions of research investigations and during technological process of their manufacture. Currently, the devices are used to specify heat treatment regimes for nitin-ol wire from various manufacturers while manufacturing vascular endo-prostheses.

The effect of reversible shape memory (RSM) is usually associated with internal-stress fields due to dislocations [1]. If these fields are oriented in a certain way, then they induce a martensite transformation with the selection of a certain martensite orientation from all crystallographically possible orientations. The selection of the preferable orientation results in macroscopic deformation of the specimen, the so-called reversible shape memory deformation henceforth called the RSM deformation. In alloys based on titanium nickelide with nickel content exceeding the equiatomic value, aging processes [2] and precipitation of the Ti3Ni4 phase occur, which produce an essential effect on the subsequent martensite transformations [3]. The present study was undertaken with the aim to clarify the role of Ti3Ni4-particles in the formation of the reversible memory effect in titanium nickelide. We established that the austenitic-type reversible-memory effect and its preservation during thermal processing of specimens are provided by precipitation of the aging-phase particles (Ti3Ni4) with preservation of the texture in the particle arrangement.

The optimum modes of thermomechanical treatment (TMT) are determined for alloy Ti – 50.7 at.% Ni (titanium nickelide, Nitinol) used in medicine for specific functional purposes. The developed modes of TMT have been used for creating a device based on the shape memory effect (SME) and the reversible shape memory effect (RSME), i.e., a self-actuating and easily removable “Crossbill” clip for urgent control of bleeding.

A technology is developed for joining of pipes using elements such as nipples or fittings made from materials with a shape memory effect. The technology ensures tightness of joints in highly loaded detachable pipeline structures, in hydraulic and pneumatic systems of agricultural machinery. Keywords pipeline, hydraulic system, pipe joint, reliability, titanium nickelide, phase transformations, fitting, shape memory effect kravchenko-in71@yandex.ru, dinara.khasyanova@mail.ru, dm_petrovsky@mail.ru, cherkasova65@mail.ru, bogolyubova@rgau-msha.ru, pav-chumakov@yandex.ru

The relevance of research on metamaterials is driven by the need to create materials with fundamentally new properties not found in nature. The ability to exhibit anomalous mechanical characteristics opens up opportunities for breakthrough applications in various industries. The development of metamaterials based on intelligent alloys, particularly titanium nickelide with a shape memory effect, enables the creation of structures that combine unique geometry with functionality, which is especially in demand for next-generation implants, energyabsorbing systems, and adaptive mechanical components. Purpose: To investigate the mechanical properties of structures made of titanium nickelidebased alloy with a shape memory effect, exhibiting both positive and negative Poisson's ratio values, as elements of metamaterial structures. Methodology: The experiment involved compression tests of two types of wire structures made of Ti-51 at. % Ni alloy. Research findings : It was found that, depending on the structure, the samples exhibited both positive and negative Poisson's ratios. The deformation curves showed almost complete shape recovery of both structures after load removal, which was confirmed experimentally.

A special class of large-sized space systems is formed by transformable structures that have different configurations in transport and operating states. Transformable large-sized space structures are delivered into orbits in a folded transport state and after that they are deployed into operating position. Now problems of the mathematical modeling of deployment dynamics of such systems attract a great interest of scientists. When the structure is transformed, impact dynamic loads arise in the system elements. To ensure a smooth «controlled» opening of the transformable structures and to exclude the dynamic impact loads in their constructed elements, it is proposed to use force actuators made of material with a shape memory effect. Now, to create mechanisms with elements made of the materials with the shape memory effect, the role of experimental methods is very important. Preliminary experimental studies of the force actuator made of such material as titanium nickelide were carried out. Deformation and force characteristics of the actuator obtained in these studies prove the possibility to use it for reliable deployment of the promising transformable space structures. Based on the fulfilled theoretical and experimental studies, the mathematical model describing the force actuator functionality is proposed.

This paper reports the results of an experimental study of unsteady processes during combustion in a half-closed volume of model condensed-material samples reinforced by elements with the shape memory effect (titanium nickelide). It is shown that the thermal and mechanical action of the elements on the combustion process makes it possible to broaden considerably the range of control of the condensed-system burning rate as compared with the well-known technique (use of wires or plates with a high heat conductivity).

An experimental method was obtained for treating semi-finished products from titanium nickelide alloys TN-1 by twisting a cylindrical sample in the austenitic state at a temperature of T = 493 K to a predetermined angular strain, after which the sample was rigidly clamped, fixing the angular deformation of the sample, and cooled to a temperature of T = 293 K. At a given temperature, the rigid jamming of the sample is eliminated, while the isothermal return of the part of the deformation obtained by twisting in the austenitic state occurs. Then the sample is heated to a temperature of T = 493 K, and there is a shape memory effect (SME), manifested in the form of restoration of angular deformation. A systematic experimental study was carried out of the dependence of the influence of the complex regime of thermal-mechanical action containing the stages of generation and relaxation of stresses on the shape memory effect. It has been experimentally established that SME during heating after cooling in the direct MT range under pinched conditions can be observed with zero deformation effect in the final heating interval.

A systematic study has been made of the shape-memory effects which arise in titanium nickelide after prestraining under isothermal conditions. It has been found that under thermal cycling in the free state a broad spectrum of phenomena is observed — repeatedly reversible shape memory, reversible deformation, deformation of an oriented transformation, etc., each of which can be realized independently of the others in the temperature range of the B2 ⇄ R and R ⇄ B19' transformations. When summing up the observed laws of the mechanical behavior of the material we used concepts of heterogeneous development of deformation in crystals, structurally hereditary properties of alloys with a shape-memory effect, as well as the principle of independent initiation of various channels of deformation.