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The paper analyzes the possibility of creating a titanium porous fiber material for implants, which is made of fibers of various transverse sizes and has gradient pore architecture. The architecture of the porous space, structure, and mechanical characteristics of such material have been studied. It is shown that the strength of the porous fiber material can be improved by increasing the temperature of diffusion bonding and by performing hydrogen heat treatment. The specifics of the mechanical behavior and fracture of the material samples were studied by performing a fixed-end bending test. [ABSTRACT FROM AUTHOR]

The effect of volume fraction and size of Ti4Ni2Ox particles on pitting, crevice, and fretting corrosion processes is studied by testing implanted elements of titanium nickelide based alloys as part of spinal pedicle screw devices in a 0.9% NaCl solution, tested elements being produced from ingots melted by various technologies (vacuum induction melting; combined skull melting with subsequent vacuum-arc remelting). It is shown that the vacuum induction melting method, which provides higher purity of the resulting material, in particular with respect to oxygen, and reduces the Ti4Ni2Ox volume fraction, is preferable for increasing titanium nickelide based alloy corrosion resistance in a biological environment. It is established that a reduction in volume fraction (and size, dmax) of Ti4Ni2Ox particles from 5.1 ± 1.2 vol.% (dmax = 10 μm) to 3.5 ± 0.7 vol.% (dmax = 7 μm) results in the pitting potential increasing from 552 ± 70 to 854 ± 123 mV and the fretting corrosion current decreasing from 11 ± 2.7 to 6.7 ± 2.8 μA. At the same time, the content of Ni ions in a test corrosion medium after crevice and fretting corrosion studies decreases from 84 ± 6 to 64 ± 5 and from 74 ± 6 to 57 ± 4 μg/liter, while the area of corrosion sites decreases by 1.3 and 1.8 times respectively. It is shown that a further reduction in Ti4Ni2Ox particle volume fraction down to 1.2 ± 0.2 vol.% (dmax = 5 μm) does not have a significant effect on corrosion resistance indices. [ABSTRACT FROM AUTHOR]

The characteristics of the shape memory effect of a silicone rubber–titanium nickelide composite material under bending deformation have been studied. It is shown that the critical deformation (), upon reaching which 0.2% of unrecoverable deformation is accumulated in the composite, can reach 36–38% (at = 9% in a reinforcing filler made of titanium nickelide). A method for calculating the mechanical behavior of a composite under bending deformation is proposed. [ABSTRACT FROM AUTHOR]

The operability of shape memory spring actuators made of titanium nickelide under constant and variable counteraction to shape recovery is investigated. Methods for calculating the maximum specific energy of the actuators using the properties of the material are proposed. These properties are shown to be the critical strains and stresses (in martensitic and austenitic states) corresponding to the beginning of slip processes and depending on the ratio of the test temperature to the shape recovery temperatures. [ABSTRACT FROM AUTHOR]

Abstract—The shape memory effect characteristics of a VT22I titanium alloy are studied during deformation by torsion. The critical strain () at which 0.3% unrecovered strain is accumulated is used as the main characteristic of the effect. This quantity for the VT22I alloy is shown to be lower by a factor of 3–4 than that for alloys based on titanium nickelide, which is due to an intense increase in the martensite/austenite interface motion resistance and to low slip stresses in a disordered solid solution. [ABSTRACT FROM AUTHOR]

It is shown that the pressure treatment of titanium nickelide alloys should be carried out in two stages. At the first stage, ingots are deformed in order to transform the brittle cast structure, while at the second stage, the necessary shape is imparted to a semi-finished product along with the required structure and material properties. The deformability of TiNi alloy ingots largely depends on the content of impurities and the uniformity of a chemical composition, which is determined by the purity of a charge material and the smelting method. The deformability can be increased on the basis of using a titanium sponge in terms of a charge and smelting ingots either by an induction method in a cold crucible unit or by the combination of skull melting with subsequent vacuum-arc remelting. At the second pressure treatment stage during the acquisition of deformed semi-finished products with the required structure and shape memory effect properties, it is necessary to consider temperature-time conditions for the development of polygonization and recrystallization processes, as well as the precipitation of Ni-rich Ti3Ni4 intermetallics. [ABSTRACT FROM AUTHOR]

The deformation- and thermal-cycle resistance of titanium nickelide-based alloys is considered. We proposed to estimate these characteristics using both fracture and the degradation of the functional characteristics of the material (shape recovery temperature, unrecoverable strain, etc.). The functional characteristics are found to be determined by the critical stresses and strains of the material, which depend on its structure and the test temperature. [ABSTRACT FROM AUTHOR]

It is shown that the structure of alloys based on titanium nickelide, obtained by industrial technology, invariably contains titanium-rich phases of type Ti2Ni/Ti4Ni2(O, N), even if the nickel concentration in the B2-phase exceeds the equiatomic composition. The volume fraction of these phases depends on the smelting method, the purity of the charge, and the technology used for subsequent ingot processing. Regression equations linking shape recovery temperatures with the concentration of nickel in the B2-phase in the quenched state are presented. On the basis of these equations, a method for calculating the volume fraction of Ti3Ni4 type particles released during aging is proposed. [ABSTRACT FROM AUTHOR]

Theoretical calculations and experimental studies were carried out making it possible to predict the maximum value of reversible deformation of a composite material based on a polymer matrix reinforced with titanium nickelide fibers. [ABSTRACT FROM AUTHOR]

The effect of the test temperature on the mechanical behavior of a titanium nickelide–based alloy is considered. The behavior of a titanium nickelide–based alloy is shown to be substantially dependent on the level of stresses and strains of the material. The critical stresses are determined by the solid-solution, grain-boundary, strain, and precipitation hardening mechanisms. The maximum critical strain can be achieved by a combination of several hardening mechanisms. [ABSTRACT FROM AUTHOR]

The composite material consisting of a carbon fiber reinforced plastic matrix and reinforcing titanium nickelide elements is studied and subjected to static and cyclic three-point bending tests. At the same rigidity, the elastic deformation and the fatigue life of the material are found to increase with the volume fraction of titanium nickelide. The developed material can be used to produce prosthetic–orthopedic medical articles. [ABSTRACT FROM AUTHOR]

The effect of the structure, the temperature, and the deformation scheme on the deformation behavior of titanium nickelide-based alloys is studied. One of the most important characteristics of the material is shown to be the temperature dependence of the critical strain corresponding to the onset of intense development of slip mechanisms. [ABSTRACT FROM AUTHOR]

The short-term creep processes in a Ti–55.7 wt % Ni alloy are investigated. Wire samples of this alloy after preliminary annealing at 450–700°C are deformed by torsion under constant loading in an air atmosphere in the temperatures range 450–550°C. The effect of structural parameters (grain size, presence of fine Ti3Ni4 particles) on the creep mechanism and rate is shown. Grain-boundary diffusion is found to be one of the main creep mechanisms. [ABSTRACT FROM AUTHOR]

Abstract—A composite material consisting of a silicone rubber matrix and nickel–titanium wire reinforcement added at different volume fractions is prepared, and its debond strength and thermomechanical behavior are studied. The debond strength of the composite can be increased by reducing the surface roughness of the embedded nickel–titanium wire to Ra = 0.16 μm. The loading rate has a considerable effect on the residual strain in this material. The composite materials with the reinforcement content of 10 to 31% subjected to a 10% pre-strain can fully recover their shape on heating, suggesting the presence of memory shape effect in these materials. [ABSTRACT FROM AUTHOR]

Abstract: The influence of a constant counteraction on the shape recovery and the specific shape recovery energy in a titanium nickelide-based alloy is considered. This energy is shown to be maximal after preliminary deformation of the material to a critical value and the external counteraction of shape recovery that corresponds to critical stresses. The specific shape recovery energy is maximal in a titanium nickelide-based alloy with the structure recrystallized at an annealing temperature of 570°C. [ABSTRACT FROM AUTHOR]

The effect of aging modes on the structure and thermomechanical behavior of alloys based on titanium nickelide and bearing the same content of nickel (55.7 wt.%) and different volume fractions of the Ti2Ni phase is studied. It is shown that the morphology of the Ti3Ni4 particles precipitated in the quenched alloy as a result of aging at 450 and 550°C and the characteristic temperatures of the martensitic transformation vary as a function of the initial content of the Ti2Ni phase. [ABSTRACT FROM AUTHOR]