Ti-Nb Alloys Research Articles

Surface Modification of Ti-Nb Alloy in Alkaline Solution to Enhance Bioactivity

Titanium alloys, especially titanium-niobium alloy have been reported as a potential biomaterial with good biocompatibility and non-toxicity. However, there is a lack of studies in alkaline surface treatment of new beta titanium alloy fabricated by vacuum arc melting (VAM) and powder metallurgy (PM) technique with high addition of niobium percentage. The purpose of this research was to examine the feasibility of surface modification on new beta Ti-40wt% Nb alloy in sodium hydroxide solution in order to form bioactive alkaline titanate layer. The characterization involved in this study is X-ray diffraction analysis (XRD), scanning electron microscope (SEM), microhardness, density measurement and optical microscope (OM). Development of amorphous alkaline titanate layer consisted of titanium hydrate, sodium titanate and oxide mixture of titanium oxide, niobium, niobium oxide were revealed by XRD. SEM shows titanate hydrogel layer form on Ti alloy PM thicker than on Ti alloy VAM. Microhardness and density measurement for Ti alloy VAM is greater than Ti alloy PM. OM shows porous surface on Ti alloy PM compare to VAM. This research suggests that the formation of sodium titanate layer on the surface of Ti-Nb alloy enhance bioactivity with better osteointegration and present higher formation of apatite which is crucial for the desired biomedical implant.

The Effect of Niobium Addition on Properties of Titanium-Based Alloy Fabricated via Mechanical Alloying

The aim of this study was to investigate the effect of niobium addition on phase formation, densification, microhardness and compressive properties of Ti-Nb alloys that possess suitable characteristics as bone fixation device. The mixture of Ti and Nb powders was mechanically alloyed (MA) in a planetary mill for two hours. The effect of Nb addition to Ti was investigated by x-ray diffraction (XRD) analysis. In addition, density, microhardness and compressive behavior of the sintered alloy were also determined by the principle of Archimedes, Vickers microhardness test and compression test, respectively. The results suggested that Nb addition has changed the phase from α-Ti to β-Ti. As the Nb addition was increased from 0 wt.% to 40 wt.%, it is observed that the density of alloy increased from 4.17 g/cm3 to 5.24 g/cm3. The microhardness and compressive modulus were 306.92 HV and 57.06 GPa for Ti-0Nb (wt.%), while the mechanical properties of the alloy dropped to 218.23 HV and 25.88 GPa when the Nb addition was up to 40 wt.%. This trend is similar to the compression strength, which the compression strength for Ti-0Nb (3221 MPa) decreased to 2123 MPa as Nb was incorporated into Ti up to 40 wt.%. It is found that Ti-40Nb possess close resemblance to the Young’s modulus of human cortical bone which lies in the range of 7-30 GPa and exhibit suitable characteristics as bone fixation device.

Diffusion mediated growth of superconducting Nb-Ti composite films by high temperature annealing

The fabrication of superconducting Nb-Ti alloy by high temperature annealing of Nb/Ti bilayer thin films is reported here. During the annealing process, Nb and Ti diffuse into each other and Nb-Ti composite film formation occurs at the interface of the bilayer. Two types of substrates, namely, SiO2/Si and Si3N4/Si are used to grow the bilayers of Nb/Ti by using dc magnetron sputtering. Annealing at temperature about 820 °C leads the substrates to take part into the diffusion process. The alloying of Nb-Ti and the effect of substrates on the structural properties are studied by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). Ti-rich Nb-Ti phases are present in the XRD while interface studies through XPS confirms the interdiffusion of the two elements Nb and Ti along with the presence of the decomposed elements from the substrates. Appearance of nitride phases in case of Si3N4/Si substrate confirms the substrate’s involvement in the diffusion process. Further low temperature transport measurements are carried out to study the superconducting properties of the Nb-Ti composite films grown on both oxide (SiO2/Si) and nitride (Si3N4/Si) substrates. Nb-Ti composite films offer higher transition temperature (T C ) compared to that of pure Nb with similar thickness used in Nb/Ti bilayer films. Higher normal state resistance (R N ) with wider transition width for Nb-Ti on nitride substrate in comparison with the oxide substrate indicates a possible role of N atoms in tuning the disorder and hence controlling the transport properties. Finally, the presented method can be used to fabricate superconducting stoichiometric NbTi and NbTiN thin films for future phase slip and superconducting single photon detector-based applications.

Influence of the Phase Composition of Titanium Alloys on Cell Adhesion and Surface Colonization.

The pivotal role of metal implants within the host's body following reconstructive surgery hinges primarily on the initial phase of the process: the adhesion of host cells to the implant's surface and the subsequent colonization by these cells. Notably, titanium alloys represent a significant class of materials used for crafting metal implants. This study, however, marks the first investigation into how the phase composition of titanium alloys, encompassing the volume fractions of the α, β, and ω phases, influences cell adhesion to the implant's surface. Moreover, the research delves into the examination of induced hemolysis and cytotoxicity. To manipulate the phase composition of titanium alloys, various parameters were altered, including the chemical composition of titanium alloys with iron and niobium, annealing temperature, and high-pressure torsion parameters. By systematically adjusting these experimental parameters, we were able to discern the distinct impact of phase composition. As a result, the study unveiled that the colonization of the surfaces of the examined Ti-Nb and Ti-Fe alloys by human multipotent mesenchymal stromal cells exhibits an upward trend with the increasing proportion of the ω phase, concurrently accompanied by a decrease in the α and β phases. These findings signify a new avenue for advancing Ti-based alloys for both permanent implants and temporary fixtures, capitalizing on the ability to regulate the volume fractions of the α, β, and ω phases. Furthermore, the promising characteristics of the ω phase suggest the potential emergence of a third generation of biocompatible Ti alloys, the ω-based materials, following the first-generation α-Ti alloys and second-generation β alloys.

Microstructure and enhanced strength-ductility of TiNbCu alloys produced by laser powder bed fusion

The β-type Ti35NbxCu alloys (x = 0, 1, 3, 5, and 7 wt%) were produced by laser powder bed fusion (LPBF) and the influence of Cu content on the microstructure and mechanical properties was studied. The results indicate that when the content of Cu is less than 3 wt%, Cu can diffuse completely into the Ti matrix to form solid solution without element segregation. Moreover, the elastic modulus of Ti35Nb1Cu alloy (49.1 ± 1.6 GPa) is reduced by 33 % compared to that of Ti35Nb alloy (73.2 ± 1.4 GPa). When the content of Cu exceeds 3 wt%, the eutectoid reaction is activated during the cyclic heating and rapid cooling of LPBF, and the partially supersaturated β phase is transformed into nano-scale α and Ti2Cu phases (β→α+Ti2Cu). Nano-scale Ti2Cu particles precipitated along β grain boundary results in a pinning effect, which inhibits the growth of β grain, hinders dislocation movement, and improves the strength of the alloy. However, when the content of Cu is 7 wt%, the dislocation density (4.179 × 1015 m−2) and the ratio of brittle phase Ti2Cu (8.5 %) are too high, and the stress concentration caused by the initiation of inherent micro-cracks are the main reason for the tensile brittle fracture of Ti35Nb7Cu alloy. As such, the Ti35Nb5Cu alloy has the highest tensile strength of 867.3 ± 24 MPa and the elongation reaches 11.7 ± 0.5 %. Therefore, solution strengthening of Cu, fine grain strengthening of β, dislocation strengthening, and precipitation strengthening of Ti2Cu are the main reasons for the excellent comprehensive mechanical properties of Ti35Nb5Cu alloy.

Nb-content-dependent passivation behavior of Ti–Nb alloys for biomedical applications

Ti–Nb alloys have the advantages of non-toxicity, low elastic modulus, high strength, and good biocompatibility. However, the effect of Nb content on its passivation behavior in Hank's solution still needs to be investigated. This work investigated the microstructure, hardness, and corrosion behavior of Ti-xNb (x = 5, 15, 25 wt%) alloys. The β phase gradually increases associated with the increasing Nb content in Ti–Nb alloys, resulting in the dispersion strengthening of alloys. Moreover, with the increased Nb content, the samples show higher open circuit potential, lower passivation current density, and higher charge transfer resistance in Hank's solution at 37 °C. When the passive films of Ti–Nb alloys are formed under the high potentials of 1 V and 2 V, the passive films gradually dissolve after the withdrawal of applied potential, representing the decrease in the total impedance of the passive film. The reason for this phenomenon is the addition of Nb substantially decreases the oxygen vacancies in the passive film formed on the samples. Therefore, the impedance of the passive film is increased.

Investigation of β/α″ interface in Ti-Nb alloy

Investigation of β/α″ interface in Ti-Nb alloy

Designing Gallium-Containing Hydroxyapatite Coatings on Low Modulus Beta Ti-45Nb Alloy

Low-modulus β-type Ti-45Nb alloy is a promising implant material due to its good mechanical biocompatibility, non-toxicity, and outstanding corrosion resistance. Its excellent chemical stability brings new challenges to chemical surface modification treatments, which are indispensable for both osteogenesis and antibacterial performance. Coatings containing metal ions as anti-microbial agents can be an effective way to reduce implant-associated infections caused by bacterial biofilm. Gallium ion (Ga3+) has the potential to reduce bacterial viability and biofilm formation on implant surfaces. In this study, a novel two-step process has been proposed for Ga3+ incorporation in hydroxyapatite (HAP) to develop bioactive and antibacterial surfaces on Ti-45Nb alloy. For the generation of bioactive surface states, HAP electrodeposition was conducted, followed by wet chemical immersion treatments in gallium nitrate (1 mM). Different buffers such as phosphate, sodium bicarbonate, ammonium acetate, and citrate were added to the solution to maintain a pH value in the range of 6.5–6.9. Coating morphology and HAP phases were retained after treatment with gallium nitrate, and Ga3+ ion presence on the surface up to 1 wt.% was confirmed. Combining Ga and HAP shows great promise to enable the local delivery of Ga3+ ions and consequent antibacterial protection during bone regeneration, without using growth factors or antibiotics.

Comparison of the Magnesiothermic Reduction Behavior of Nb2O5 and Ti2Nb10O29

Nb-Ti binary alloys are widely employed as high value-added materials in the manufacture of super heat-resistant alloys, biomaterials, and superconductors. Therefore, there is significant interest to produce Nb-Ti master alloys in a cost-effective manner. In this study, we investigated the magnesiothermic reduction of Nb2O5 and Ti2Nb10O29 over the temperature range of 1073 to 1223 K and comparatively evaluated the reaction outcomes. The reduction product was composed of metal (Nb or Nb-Ti) particles and MgO, which covered the surface of the reduced metal particles. After the reduction reaction, the surface MgO phase was removed by pickling with hydrochloric acid (HCl) to finally recover the Nb metal or Nb-Ti alloy as a pure product. Scanning electron microscopy and X-ray diffraction analyses of the pure Nb metal and Nb-Ti alloy powders revealed that the reduction of both raw materials was successful at temperatures exceeding 1173 K. Reaction kinetics analysis revealed that the activation energy for the reduction of the mixed metal oxide (Ti2Nb10O29) is lower than that of Nb2O5 reduction. This is because of the different reaction mechanism behaviors during reduction and the different thermodynamic stabilities of the precursors.

The interdependence of the thermal and mechanical cycling behaviour in Ti2448 (Ti–24Nb–4Zr–8Sn, wt%)

Metastable β Ti alloys based on the Ti–Nb system have received increased attention in recent years due to an attractive range of properties. This includes their ability to undergo martensitic phase transformations on application of a stress, or on cooling below a critical temperature. However, the cyclic behaviour of these materials is unstable, which is a significant barrier to widespread industrial use. Recently, both the thermal and mechanical aspects of the transformation have been shown to be highly sensitive to the presence of internal stresses, which include a contribution from the dislocations produced as a necessary product of the transformation to provide geometric continuity at the phase boundary. It has been hypothesised that these dislocations may be responsible for the unstable cyclic behaviour. Redistribution of these dislocations and their associated stresses at elevated temperatures provides a novel mechanism by which unstable cyclic behaviour can be mitigated. Hence, in this work, in situ synchrotron characterisation is used to assess the effect of thermal cycling subsequent to mechanical loading on the superelastic transformation in a commercial Ti–Nb alloy. For the first time, it was shown that unstable cyclic behaviour can be avoided through the use of inter-cycle thermal treatments, which represents a significant breakthrough in our understanding of Ti–Nb superelastic materials.

On the stability and formation of the α″ and ω phases in Ti-Nb alloys upon cooling

Metastable β-Ti alloys based on the binary Ti-Nb system can exhibit a stress induced transformation to the α″ phase allowing superelasticity and shape memory behaviours but they are also susceptible to the formation of the hexagonal ω phase. The presence of ω is widely reported to prevent the α″ transformation, and in certain forms embrittles the material. Most studies characterise the ω phase ex situ and only observation of the ω phase is used to predict its stability. This approach ignores different potential formation mechanisms and results in an ambiguous picture of its true stability. Here, through the use of in situ synchrotron X-ray diffraction we establish the true nature of the α″ and athermal ω phase transformations with respect to both temperature and composition in a series of cold rolled Ti-Nb alloys which initially contained both α″ and ω. Across the range of studied alloys, the α″ start temperature was always found to be above the ω start temperature but both phases were observed to grow simultaneously contradicting previous reports. In addition, the ω start temperature in all alloys was found to be ≤ 10˚C indicating that the ω present in the initial microstructures was metastable. These observations contradict a vast swathe of the conclusions drawn from ex situ data regarding the stability of the ω phase and categorically show that observation of this phase alone cannot be used to establish its stability and the relevant thermodynamic temperature, ωs.

Comparison of GUMMETAL® and stainless steel alloy during canine retraction: A pilot split-mouth randomized controlled trial

A TiNb alloy wire (GUMMETAL® [GM], Toyota Central R&D Labs, Inc., Nagakute, Japan) was recently developed with unique properties for orthodontic applications. This pilot split-mouth randomized controlled trial compared maxillary canine retraction during space closure using sliding mechanics on GM vs. stainless steel (SS) archwires. Subjects who met the inclusion criteria were treated with fixed appliances and maxillary first-premolar extractions between September 2020 and March 2022. After leveling and aligning, maxillary archwires, fabricated by crimping together segments of 0.016×0.022" GM and SS archwires, were placed and canine retraction initiated using nickel-titanium coil springs. Digital models of the maxillary arch were superimposed at 0, 4, 8 and 12 weeks and the amount of canine movement (mm), rate of movement (mm/month), and 3-dimensional changes (rotational, vertical extrusion, tip) were measured and compared statistically. Of the 12 subjects recruited, only six completed the study with a median age of 15.8 years (12.0-17.4 years). At 12 weeks, the median canine retraction was 3.41mm (IQR: 2.10, 4.76) with GM versus 3.71mm (IQR: 1.62, 6.45) with SS. The retraction rate was 1.14mm/month (IQR: 0.69, 1.59) with GM, versus 1.24mm/month (IQR: 0.54, 2.15) with SS. The median rotational, vertical and tip changes of the canine were 7.90̊, 0.59mm and 6.15̊ with GM, and 7.25̊, 0.29mm and 2.05̊ with SS. Intergroup differences with all measurements were not statistically significant. No significant differences were found between GM and SS during maxillary canine retraction. GM demonstrated clinical potential for space closure mechanics, however, future larger studies are needed.

Microstructure and corrosion resistance of Ti and Ti-40Nb alloy modified by plasma electrolytic oxidation in tricalcium phosphate suspension

Commercially available, modification of the surface of the modification of the surface of the Ti CP and Ti-40Nb alloys by plasma electrolytic oxidation in a tricalcium phosphate suspension with silver nitrate has been reported. The determined characteristics of the obtained coatings were related to microstructural studies, chemical composition, wettability, and corrosion tests. The proposed treatment ensured the effective incorporation of bioactive compounds into the oxide coatings. Electrochemical corrosion tests showed superior corrosion resistance for both substrates, with higher corrosion resistance obtained for Ti-40Nb samples in baths containing silver nitrate. The presented research highlighted the potential application of PEO treatment of Ti alloys for the purpose of hard tissue implants.

Effect of prior processing on the decomposition of the β phase in Ti–Nb alloys during intermediate heat treatments

Metastable β-Ti alloys exhibit multiple decomposition pathways during isothermal ageing. Ages at intermediate temperatures below the α/β transus result in the formation of α or isothermal ω. The effect of prior processing on these pathways remains largely unexplored within the literature. Therefore, the role of processing on a Ti–Nb alloy was investigated in cold rolled and solutioned conditions. The solutioned sample showed evidence of recrystallisation, with shear bands remnant from the prior cold rolling that exhibited a greater degree of texture than the surrounding material. During isothermal ageing ωiso was observed outside of these bands whilst α phase precipitated within the bands and throughout the cold rolled sample. This shows that the remnant strain from the rolling process facilitated α nucleation over ωiso due to accommodation of the α/β interface. Additionally, it was seen that the magnitude of internal strains had a marked effect on the α morphology observed.

Design, processing, and biocorrosion study of Ti–30Nb alloy with low elastic modulus for bioimplant applications

This study aims to design and process Ti–30Nb at% alloy with improved biocorrosion protection and lower elastic modulus for use as a bioimplant material in orthopedic applications. The influence of sintering temperature on phases, microstructure, microhardness, and modulus of elasticity was investigated. The surface energy of the alloy was evaluated and the bio-corrosion study was carried out in a simulated body medium. According to the findings, Ti–30Nb alloy consisted primarily of β-Ti, with traces of α-Ti and α” phases. Increasing the sintering temperature enhanced the density and microhardness. The developed Ti–30Nb alloys have a modulus of (55–78.9) GPa, which is lower than that of commercial Ti6Al4V alloy and CP-Ti. The surface energy of the designed Ti–30Nb alloys was 18.5% more than that of the commercial Ti6Al4V alloy. The obtained in vitro corrosion results confirmed the beneficial impact of sintering temperatures on the enhancement of the corrosion protection of binary Ti–30Nb alloy.

Discontinuous dynamic recrystallization of TiNb alloys: Experiment and cellular automaton simulation

Discontinuous dynamic recrystallization of TiNb alloys: Experiment and cellular automaton simulation

Investigations of the Wettability and Electrochemical Corrosion Behavior of Nb2O5 Thin Films on a Ti45Nb Alloy

Investigations of the Wettability and Electrochemical Corrosion Behavior of Nb2O5 Thin Films on a Ti45Nb Alloy

Enhanced wear resistance and surface properties of oxide film coating on biocompatible Ti45Nb alloy by anodization method

β-Titanium alloys have become increasingly popular as biomaterials because of their low modulus of elasticity and superior corrosion properties in recent years. β-titanium alloy containing niobium is also a biocompatible and non-toxic material. Among β-Ti alloys, Ti45Nb is one of the most remarkable alloys for its superior properties as a biomaterial. This alloy has superior properties due to low elasticity modulus and non-toxic elements, but its surface properties are inadequate for biomaterial applications. Therefore, various surface treatments are applied to improve the surface properties of these alloys. In this study, an oxide film layer was formed on the Ti45Nb surface under different potential conditions by the anodizing method. The effects of these factors on friction, wear, and contact angle measurements were investigated. The structural properties of the oxide film coated samples were analyzed with XRD and their surfaces and cross-sectional images were observed by SEM. Also, the surface roughness and nanoindentation tests were performed. In this regard, it was determined that oxide film thickness, surface roughness and hardness increased with the increase of anodization potential. The contact angle of the samples decreased with the increase in the anodization potential and the surface tension of the materials increased. The highest nanohardness of about 4.19 GPa was obtained from 150 TA samples. The elasticity modulus of the untreated sample was about 63 GPa, while the anodized samples ranged from an average of 31 to 83 GPa. The wear results revealed that the anodization process improved the wear resistance of the Ti45Nb alloy. As a result, the sample anodized at 200 V for 30 min exhibited optimum surface roughness, morphology and high wear resistance.

Composition- and temperature-dependence of β to ω phase transformation in Ti-Nb alloys

ω phases have shown great effects on the superelasticity and modulus of metastable β-Ti alloys. In this study, the microstructure evolution during cooling and aging for β → ω phase transformation is investigated by integrating a thermodynamic database with phase field simulations. Our CALPHAD calculations based on an available thermodynamic database give the Gibbs energies of metastable β (Nb-lean β1 + Nb-rich β2 produced via spinodal decomposition) and ω phases in Ti-Nb. Informed by the results, our phase field simulations show that the formation mechanisms of ω exhibit dependence on the composition and temperature. The ω can form in Ti-26 at.% Nb without the assistance of spinodal decomposition. Further analysis shows that the precursory spinodal decomposition in the β phase occurs in Ti-50 at.% Nb, and could induce geometrically confined ω. The novel transformation pathway could create unique morphology of ω. This study could elucidate new insights into the ω phase transformation in Ti-Nb alloys and metastable β-Ti alloys having spinodal decomposition.

Assessment of Microstructural, Mechanical and Electrochemical Properties of Ti-42Nb Alloy Manufactured by Electron Beam Melting.

The β-type Ti-42Nb alloy has been successfully manufactured from pre-alloyed powder using the E-PBF method for the first time. This study presents thorough microstructural investigations employing diverse methodologies such as EDS, XRD, TEM, and EBSD, while mechanical properties are assessed using UPT, nanoindentation, and compression tests. Microstructural analysis reveals that Ti-42Nb alloy primarily consisted of the β phase with the presence of a small amount of nano-sized α″-martensite formed upon fast cooling. The bimodal-grained microstructure of Ti-42Nb alloy comprising epitaxially grown fine equiaxed and elongated equiaxed β-grains with an average grain size of 40 ± 28 µm exhibited a weak texture. The study shows that the obtained microstructure leads to improved mechanical properties. Young's modulus of 78.69 GPa is significantly lower than that of cp-Ti and Ti-6Al-4V alloys. The yield strength (379 MPa) and hardness (3.2 ± 0.5 GPa) also meet the criteria and closely approximate the values typical of cortical bone. UPT offers a reliable opportunity to study the nature of the ductility of the Ti-42Nb alloy by calculating its elastic constants. XPS surface analysis and electrochemical experiments demonstrate that the better corrosion resistance of the alloy in SBF is maintained by the dominant presence of TiO2 and Nb2O5. The results provide valuable insights into the development of novel low-modulus Ti-Nb alloys, which are interesting materials for additive-manufactured implants with the desired properties required for their biomedical applications.