Ti-Nb Alloys Research Articles

Fabrication of Be-Ta Ti Alloys without Pre-Alloyed Powders via SLM

In this study, we sucsess the fabrication of dense compornent of Ti-20at.%X (X = Cr and Nb) alloys by Selected laser melting (SLM) pwocess, from a mixture of poweder element powders. The volume rasio of pore and non-molten particles is dependent of the enegy density. The difficulty of fabrication of Ti-X alloy comporment is dependent of melting temperature of X element. Thus, Ti-20at.%Cr alloys, which has the lowest melting temperature of X is easier to monufacture of dense comporment. The Ti-20at.%Cr alloys and Ti-20at.%Nb comprise β-Ti single-phase components without any non-molten particles and macroscopic defects. In addtion, the {001}〈100〉 crystallographic texture of these Ti-Cr and Ti-Nb alloys can be controlled effectively by optimizing the SLM parameters. This means that the SLM is key techmelogy of controlling of Young’s modulus and shape at the same time because Young's modulus of be-ta phase in Ti alloys is strongly related to the crystal orientation.

О влиянии термической обработки сплава Ti-45Nb в ультрамелкозернистом состоянии на его структурные характеристики и теплоемкость

The effect of heat treatment of the Ti-45Nb alloy in the UFG state on its structural parameters (lattice parameters, volumetric phase ratio, sizes of coherent scattering regions, residual normal stresses) and their relationship with heat capacity have been studied. It has been established that the different character of the temperature dependence of the heat capacity for the Ti-45Nb alloy in the UFG and CC states is associated with the structural-phase features of the alloy in the UFG state: the two-phase structure of a-grains and b-grains, dispersion-hardened by the ω-phase, and phase transitions in the temperature range 400-600 °С.

Role of Silicon in the Microstructural Development and Properties of Ti-15Nb-xSi Alloys for Biomedical Applications

Ti-Nb alloys are attractive for biomedical implants and the addition of Si can lead to an improved set of properties. This study investigates the effect on the microstructures and properties of solution-treated Ti-15Nb-xSi alloys followed by furnace cooling (FC), and water quenching (WQ). Based on the results, Si acts as a β-stabilizing element by increasing the β volume fraction from 13%–36% in FC samples to a range from 0%–0.55% Si. The elastic modulus decreased under both conditions and reached approximately 63 GPa in WQ samples with 0.35% Si due to an increased α” unit cell volume. On the other hand, hardness increased with increased Si content under FC and WQ conditions to a maximum of 313 HV in the WQ sample containing 0.55% Si.

Comparison of Mechanical and Structural Properties of Nickel-titanium Alloy with Titanium-molybdenum Alloy and Titanium-niobium Alloy as Potential Metals for Endodontic Files.

The objective of this study was to compare the mechanical and structural properties of the nickel-titanium (Ni-Ti) alloy already used in endodontics with titanium-molybdenum (Ti-Mo) and titanium-niobium (Ti-Nb) alloys to determine if these can be suggested in the manufacture of endodontic files. Orthodontic wires made of the different alloys were used. The previously mentioned alloys were characterized by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and torsion tests. Cyclic fatigue tests were performed on a simulated canal with a curvature of 86° to 375 rpm. The fractured surfaces of the wires were observed by means of scanning electron microscopy (SEM). A Kruskal-Wallis test and U Mann Whitney test were used to determine significant differences in cyclic fatigue between groups. In the mechanical tests, similar values of torsion were found for the three alloys. In XRD, the Ti-Nb showed less structural changes. In the cyclic fatigue test, Ti-Nb was found to be significantly more resistant with respect to Ni-Ti and Ti-Mo. Based on our in vitro study, Ti-Nb is suggested as a possible alloy for the manufacture of rotary files due to its impressive properties.

Exploration of the Sparck Plasma Sinter Technique for the Manufacture of Implants for Orthopedic Applications: Development of A High-Performance Nbti-Swcnts Nanocomposite Welded Tv6a Alloy and Densification of Preforms

Nanocomposite Ti 50 wt% Nb with and without reinforcement of carbon nanotubes were successfully fabricated by ball milling of Ti, Nb and SWCNTs (single walled carbon nanotubes) nanopowder mixture folloyed by field actived spark plasma sintering process (FASPS) for biomedical application, superconductivity and magnetism in the ITER Project. The use of brittle Ti powder, instead of ductile elemental powder, led to significant increment in the yield of mechanically alloyed powder. The powder consisted of homogeneously distributed nano-sized Ti/Nb particles together with micronsized pure Nb particles. Sintering of the powders under low temperature and pressure conditions (1273 K, 1473 K and P=50 Mpa) resulted in the fine-grained heterogeneous microstructure consisting of α and β phases. On the other hand, sintering at higher temperatures (1473 K) resulted in a relatively coarse-grained chemically homogeneous microstructure with almost complete phase. Coarse-grained homogeneous β NbTi alloy exhibited higher average hardness as compared to that of heterogeneous fine grained microstructures. An attempt has been made to illustrate the correlation between the microstructural characteristics and mechanical properties of the sintered Ti50Nb compacts. To studies and to develop the influence of SWCNTs on the behavior of the nanocomposite TiNb/SWCNTs and the welding joint interface between TA6V and nanocomposite by sparck plasma sintering. At last, the continuation of the work has been discussed and prepared, planning dynamic flexion tests to measure the NbTi, NbTi/CNTs, NbTi/SWCNTs,/TA6V fatigue limit and developing a computer processing chain in order to customize prostheses respecting patients’ morphology. The fluid ethanchied lubrification of the prosthesis articulation is currently also in study and preparation. Then, a change of scale made possible by the use of an industrial size SPS machine led to the realization of types of blade perform according to patent morphology. These results led to the filing of a patent.

Особливості формування поруватої структури стопів Zr–Ti–Nb під час їх синтезу із сумішей гідрованих порошків

Особливості формування поруватої структури стопів Zr–Ti–Nb під час їх синтезу із сумішей гідрованих порошків

Tribological and thermal properties of plasma nitrided Ti45Nb alloy

In this study, the effects of plasma nitriding surface treatment on the structural, tribological and thermal properties of Ti45Nb Beta alloy were investigated experimentally. Plasma nitriding process of Ti45Nb alloy was performed in 25% Ar-75% N2 gas mixture, for treatment times of 1–4 hours at the temperatures of 700–750 °C. The tribological tests of the plasma nitrided alloy were performed in dry sliding conditions. Thermal property measurements were applied to the plasma nitrided samples to determine their thermal conductivity and specific heat capacity. The TiNbN2 phase was observed in the compound layer formed after the nitriding process, and the compound layer and diffusion layer thicknesses increased depending on the nitriding temperature and duration. The highest microhardness was obtained for the sample nitrided at 750 °C for 4 hours and the hardness approximately twice increased compared to the untreated alloy. Due to its high surface hardness and nitride layer with sufficient thickness, the lowest wear rate was obtained for the nitrided sample under these conditions. As a result, the most effective parameter on the wear properties of Ti45Nb alloy after nitriding was determined as the process temperature. After the plasma nitriding process, thermal conductivity, thermal diffusion and specific heat capacity values decreased due to the formation of a nitride layer on the surface with a relatively lower thermal conductivity compared to the untreated alloy.

Nonlinear dynamics and stages of damage of Ti6Al4V and Ti45Nb titanium alloys in very high cycle fatigue

The paper presents an experimental methodology aimed at evaluating a very-high cycle resource for aviation titanium alloys Vt-6 (Ti6Al4V) and Ti45Nb for medical applications with different microstructures (large-crystal and submicrocrystalline ones). The submicrocrystalline (SMC) state was obtained by an intensive plastic deformation realized in two ways: the three-dimensional forging for Ti45Nb and radial-shear rolling for Ti6Al4V. The experimental program tests high-cycle and very-high-cycle loading (number of cycles 107-109) realized using the in situ determination method of the accumulation of the irreversible fatigue damage by analyzing nonlinear forms of feedback in a closed system ultrasonic fatigue setup. This makes it possible to establish the connection of the microscopic fatigue mechanisms with the model views and consider the stages of the damage development based on the nonlinear kinetics of the defect accumulation under cyclic loading in high- and gigacycle fatigue modes. We established various relations between changes in the amplitude of the second harmonic of vibrations of the free end of the samples with different internal structures, which are associated with the mechanisms of stress relaxation and damage accumulation. The grain size reduction in Ti45Nb alloy by the three-dimensional forging improved the fatigue properties by 1.3-1.5 times, whereas for VT-6 alloy, the radial-shear rolling method could not increase the fatigue properties in the very high cycle fatigue range, which may be caused by the presence of large residual internal stresses. Based on the scale parameters obtained earlier from the fracture surface morphology and the relations established in this work, the kinetic equations for the origin and growth of fatigue cracks in the gigacycle loading range will be constructed. This equation, based on the empirical power parameters related to the structure of the material, will allow us to determine the number of cycles for the origin of an internal crack and its growth to the surface.

The strong influence of Ti, Zr, Hf solutes and their oxidation on microstructure and performance of Nb3Sn superconductors

Over the last few years a new type of Nb3Sn superconducting composite based on the internal oxidation approach has emerged and has demonstrated performance significantly superior to conventional Nb3Sn. It requires a supply of O and the use of a Nb alloy – Nb-X, where X is a solute element that can be selectively oxidized to form oxide particles within the Nb3Sn. Such oxide particles not only refine Nb3Sn grain size, but also have the proper size to act as artificial pinning centers (APC) directly restraining fluxon motion, and thus dramatically improve superconducting properties. In this article we show that the size and volume fraction of the oxide particles determine both the levels of grain refinement and the shift in the peak field of the flux pinning force (Fp-B) curve. We explore the factors influencing the microstructure and properties, which we find include: selection of the solute element X, solute content, O content, and heat treatment. For the selection of X, we searched the periodic table for all promising candidates but focused down on the group-IVB elements (Ti, Zr, Hf) here as the drawability of Nb3Sn wires made from Nb-Ti, Nb-Zr, and Nb-Hf alloys has been demonstrated in the past few decades. We found that while internally oxidizing Nb-1.5 at.%Ti led to negligible grain refinement and Fp-B peak shift, Nb-Zr alloys led to much more dramatic results, and internally oxidizing Nb-Hf alloys led to the strongest grain refinement and Fp-B peak shift. For Hf alloying in particular, we compared our internal oxidation method with another method for grain refinement, which uses Hf alloying itself without oxidation, and found that internal oxidation led to much stronger grain refinement and Fp-B peak shift. We also found that higher solute content and lower reaction temperature led to stronger grain refinement and Fp-B peak shift. We conclude with a discussion of the possible mechanisms for the influence of these factors.

Highly Selective, Defect-Induced Photocatalytic CO2 Reduction to Acetaldehyde by the Nb-Doped TiO2 Nanotube Array under Simulated Solar Illumination

The adsorption and activation of CO2 molecules on the surface of photocatalysts are critical steps to realize efficient solar energy-induced CO2 conversion to valuable chemicals. In this work, a defect engineering approach of a high-valence cation Nb-doping into TiO2 was developed, which effectively enhanced the adsorption and activation of CO2 molecules on the Nb-doped TiO2 surface. A highly ordered Nb-doped TiO2 nanotube array was prepared by anodization of the Ti-Nb alloy foil and subsequent annealing at 550 °C in air for 2 h for its crystallization. Our sample showed a superior photocatalytic CO2 reduction performance under simulated solar illumination. The main CO2 reduction product was a higher-energy compound of acetaldehyde, which could be easily transported and stored and used to produce various key chemicals as intermediates. The acetaldehyde production rate was over ∼500 μmol·g-1·h-1 with good stability for repeated long-time uses, and it also demonstrated a superior product selectivity to acetaldehyde of over 99%. Our work reveals that the Nb-doped TiO2 nanotube array could be a promising candidate with high efficiency and good product selectivity for the photocatalytic CO2 reduction with solar energy.

A promising method to develop TiO2-based nanotubular surfaces on Ti-40Nb alloy with enhanced adhesion and improved tribocorrosion resistance

Although TiO2 nanotubes have unique properties making them attractive for variety of applications, their poor adhesion to the substrate is a major limitation. In order to overcome this limitation, a facile route, combination of a two-step anodic treatment and heat treatment was applied in order to develop a well-adhered TiO2-based nanotubular surface on Ti-40Nb alloy. The adhesion of the nanotubular layer was evaluated by Daimler-Benz Rockwell C test. Corrosion and tribocorrosion behavior was investigated in phosphate-buffered saline solution (PBS) at body temperature. Corrosion behavior was examined by potentiodynamic polarization and electrochemical impedance spectroscopy whereas tribocorrosion behavior was evaluated by reciprocating sliding against an alumina ball at open circuit potential. Results showed that the adhesion, corrosion, and tribocorrosion behavior of the nanotubular layer was drastically improved with the combination of a two-step anodic treatment and heat treatment.

Corrosion and Tribocorrosion Behaviors for TA3 in Ringer’s Solution after Implantation of Nb Ions

Ti alloys are prone to corrosion and wear due to the hostile environment in bodily fluids, but the Ti-45Nb alloy is considered to be a promising titanium alloy with excellent biocompatibility and resistance to physiological corrosion. In this study, Nb ions were implanted into a TA3 alloy and the effect on the biological corrosion as well as tribocorrosion behavior of TA3 in Ringer’s solution was systematically investigated. The surface microstructure and XRD results revealed that the implanted samples showed a smoother surface due to the sputtering and radiation damages, and the Nb ions mainly existed in the alloy as the solid solution element. The electrochemical polarization tests showed that the implantation of Nb ions can increase the corrosion potential of the samples, showing a better thermodynamic stability. The tribocorrosion tests showed that the implanted samples exhibited a better thermodynamic stability in a corrosive environment accompanied by wear behavior, and the worn surface showed fewer pitting pits, indicating a better corrosion resistance. However, the abrasive wear and oxidation wear degree of the sample increased because of partial softening of the surface and brittle passivation film.

First-principles study of the robust superconducting state of NbTi alloys under ultrahigh pressures

A recent experiment reported that robust superconductivity appears in NbTi alloys under ultrahigh pressures with an almost constant superconducting $T_c$ of ~19 K from 120 to 261.7 GPa [J. Guo et al., Adv. Mater. 31, 1807240 (2019)], which is very rare among the known superconductors. We investigate the origin of this novel superconducting behavior in NbTi alloys based on density functional theory and density functional perturbation theory calculations. Our results indicate that the pressure tends to transform NbTi alloys from a random phase to a uniformly ordered crystal phase, and the exotic robust superconductivity of NbTi alloys can still be understood in the framework of BCS theory. The Nb element in NbTi alloys plays a dominant role in the superconductivity at low pressure, while the NbTi crystal with an alternative and uniform Nb and Ti atomic arrangement may be responsible for the stable superconductivity under high pressures. The robust superconducting transition temperature of NbTi under ultrahigh pressure can be explained by a synergistic effect of the enhanced phonon frequency, the modestly reduced total electron-phonon coupling, and the pressure-dependent screened Coulomb repulsion.

New nanoscale artificial pinning centres for NbTi superconductors

The efficiency of new artificial pinning centres have been investigated in NbTi using the oxide dispersion strengthening (ODS) concept more typically applied to steels and Ni-superalloys. NbTi alloys containing a dispersion of nanoscale Y2Ti2O7 particles have been successfully manufactured through a powder metallurgy route by mechanical alloying Nb, Ti and Y2O3 nanopowders using high energy ball milling and subsequent consolidation and annealing. The microstructure and superconducting properties of the NbTi-Y2O3 have been characterised after each processing step. After 40 h of ball milling, the Y2O3 particles are dissolved into the nanostructured NbTi matrix formed by mechanical alloying of Nb and Ti. On annealing at temperatures above 800 °C the dissolved Y and O react with Ti from the matrix, and fine Y2Ti2O7 particles (<5 nm) are precipitated. These NbTi-Y2Ti2O7 composites showed excellent superconducting performance, with JC of 5.2 kAmm−2 at 4.2 K, 5 T, considerably higher than Y2O3-free bulks manufactured using the same process and NbTi wires manufactured using the conventional thermomechanical process. The results suggest that ODS powder processing is a promising new route to manufacture NbTi alloys containing artificial pinning centres that give superior superconducting properties.

Improved structural, mechanical, corrosion and tribocorrosion properties of Ti45Nb alloys by TiN, TiAlN monolayers, and TiAlN/TiN multilayer ceramic films

In this study, TiN, TiAlN monolayers, and TiAlN/TiN multilayer ceramic films on the surface of Ti45Nb substrates were formed via the cathodic arc physical vapour deposition process. The samples were characterized by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy, nano-indentation testing and surface tension testing. The corrosion performance of the samples was evaluated via potentiodynamic polarization and electrochemical impedance spectroscopy measurements and their tribocorrosion behaviour was evaluated by a ball on flat reciprocating tribotester in which the tribological contact was immersed in the electrolyte. The obtained structural and mechanical results indicated that multilayer films have finer grain sizes, and more stable and harder film structures compared with the monolayer coatings. Moreover, the surfaces of the samples exhibited different wetting characteristics. While uncoated and single layer (TiN, TiAlN) coatings showed hydrophilic behaviour, the multilayer coating exhibited hydrophobic behaviour. During the corrosion and tribocorrosion tests, all of the coatings showed a protective feature due to the ceramic structure of the coatings against corrosion and tribocorrosion. Among all of the ceramic coatings, the best results were obtained for the multilayer film.

Zn- or Cu-containing CaP-Based Coatings Formed by Micro-Arc Oxidation on Titanium and Ti-40Nb Alloy: Part II-Wettability and Biological Performance.

This work describes the wettability and biological performance of Zn- and Cu-containing CaP-based coatings prepared by micro-arc oxidation on pure titanium (Ti) and novel Ti-40Nb alloy. Good hydrophilic properties of all the coatings were demonstrated by the low contact angles with liquids, not exceeding 45°. An increase in the applied voltage led to an increase of the coating roughness and porosity, thereby reducing the contact angles to 6° with water and to 17° with glycerol. The free surface energy of 75 ± 3 mJ/m2 for all the coatings were determined. Polar component was calculated as the main component of surface energy, caused by the presence of strong polar PO43− and OH− bonds. In vitro studies showed that low Cu and Zn amounts (~0.4 at.%) in the coatings promoted high motility of human adipose-derived multipotent mesenchymal stromal cells (hAMMSC) on the implant/cell interface and subsequent cell ability to differentiate into osteoblasts. In vivo study demonstrated 100% ectopic bone formation only on the surface of the CaP coating on Ti. The Zn- and Cu-containing CaP coatings on both substrates and the CaP coating on the Ti-40Nb alloy slightly decreased the incidence of ectopic osteogenesis down to 67%. The MAO coatings showed antibacterial efficacy against Staphylococcus aureus and can be arranged as follows: Zn-CaP/Ti > Cu-CaP/TiNb, Zn-CaP/TiNb > Cu-CaP/Ti.

Fabrication, characterization, and in vivo biocompatibility evaluation of titanium-niobium implants.

In this study, biocompatible titanium-niobium (Ti-Nb) alloys were fabricated by using powder metallurgy methods. Physical, morphological, thermal, and mechanical analyses were performed and their in vivo compatibility was evaluated. Besides α, β, and α″ martensitic phases, α+β Widmanstätten phase due to increasing sintering temperature was seen in the microstructure of the alloys. Phase transformation temperatures of the samples decreased as Nb content increased. The ratio of Nb in the samples affected their mechanical properties. No toxic effect was observed on implanted sites. This study shows that Ti-Nb alloys can be potentially used for orthopedic applications without any toxic effects.

Zn- or Cu-Containing CaP-Based Coatings Formed by Micro-arc Oxidation on Titanium and Ti-40Nb Alloy: Part I-Microstructure, Composition and Properties.

Zn- and Cu-containing CaP-based coatings, obtained by micro-arc oxidation process, were deposited on substrates made of pure titanium (Ti) and novel Ti-40Nb alloy. The microstructure, phase, and elemental composition, as well as physicochemical and mechanical properties, were examined for unmodified CaP and Zn- or Cu-containing CaP coatings, in relation to the applied voltage that was varied in the range from 200 to 350 V. The unmodified CaP coatings on both types of substrates had mainly an amorphous microstructure with a minimal content of the CaHPO4 phase for all applied voltages. The CaP coatings modified with Zn or Cu had a range from amorphous to nano- and microcrystalline structure that contained micro-sized CaHPO4 and Ca(H2PO4)2·H2O phases, as well as nano-sized β-Ca2P2O7, CaHPO4, TiO2, and Nb2O5 phases. The crystallinity of the formed coatings increased in the following order: CaP/TiNb < Zn-CaP/TiNb < Cu-CaP/TiNb < CaP/Ti < Zn-CaP/Ti < Cu-CaP/Ti. The increase in the applied voltage led to a linear increase in thickness, roughness, and porosity of all types of coatings, unlike adhesive strength that was inversely proportional to an increase in the applied voltage. The increase in the applied voltage did not affect the Zn or Cu concentration (~0.4 at%), but led to an increase in the Ca/P atomic ratio from 0.3 to 0.7.

Microstructural study of Ti[sbnd]45Nb alloy before and after HPT processing using experimental and ab initio data mining approach

Potential application of the Ti45Nb (mass%) alloy in biomedicine as a hard-tissue replacement material puts the improvement of the alloy mechanical and biological compatibility in the research focus. Selection of the appropriate alloy production and post-production parameters influence the appearance of the favorable alloy microstructural characteristics and in turn, increase the possibility of its successful biomedical application. The high-pressure torsion (HPT) is one of the post-processing methods which enables the severe plastic deformation of the difficult-to-deform materials resulting in the higher material compatibility with biological systems. The scope of the present research was to investigate the microstructural characteristics of the Ti45Nb alloy before and after the HPT deformation using the experimental and theoretical methods. The electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used to analyze the Ti45Nb alloy microstructure. Significant grain refinement induced by HPT processing was confirmed. Possible appearance and coexistence of multiple metastable phases in the Ti45Nb alloy microstructure reported in the literature led to the additional alloy microstructural characterization using the X-ray diffraction (XRD) technique. Additional XRD investigations revealed that along with the β-Ti phase in the alloy microstructure the supplementary Ti4Nb phase is present before and after the HPT process application. The appearance of the Ti4Nb phase in the alloy microstructure was confirmed by ab initio modeling. Furthermore, additional structures were predicted and studied using a combination of data mining and first-principles calculations in the Ti4Nb compound. The five most relevant structure candidates are fully structurally determined and the proposed SrSn4 modification with orthorhombic symmetry which crystallizes in space group Cmcm (no. 63) is found to be in the best agreement with the obtained XRD results.

The influence of microstructural condition on the phase transformations in Ti-24Nb (at.%)

Ti-Nb based alloys exhibit superelastic and shape memory properties over a wide range of temperatures, making them attractive for industrial applications. However, within the literature there are significant variations in the reported transformation behaviour for a given composition that remain unexplained. These variations are problematic to engineering design and limit the industrial uptake of these alloys. To investigate the source of these discrepancies, the transformation behaviour of Ti-24Nb (at.%) in two significantly different microstructural conditions, following cold rolling (CR) and following a subsequent solution heat treatment (ST), has been studied using in situ synchrotron diffraction data whilst undergoing a three step thermal cycle. When cooling from 350 to -196˚C, the CR condition material underwent both the β to αʺ and β to ω transformations, whilst only the β to ω transformation was observed in the ST condition material. These results show that the transformation behaviour of Ti-Nb alloys, in particular the β to αʺ transformation, is significantly influenced by prior processing and that theories of mutual exclusivity between αʺ and ω phase formation need revisiting. In addition, several features within the datasets were inconsistent with a solely thermally driven martensite formation mechanism and an alternative description that includes other factors is discussed.