Ti-Nb Alloys Research Articles

Spall damage of TiNb alloys under Taylor-wave loading

Spall damage of two cast TiNb binary alloys, Ti75Nb25 and Ti50Nb50, is investigated under Taylor-wave loading at different impact velocities. The dynamic yield stresses are similar for both alloys (∼1.2 GPa). The incipient spall strength of Ti75Nb25 (3.2 GPa) is considerably lower than that of Ti50Nb50 (4.3 GPa). The damage in Ti75Nb25 is ductile in nature, and abundant {332}〈113〉 deformation twins are activated. For Ti50Nb50, only a small amount of {112}〈111〉 deformation twins are observed, and cracks are along grain boundaries or along the {112} planes in a grain interior, leading to the typical brittle spall failure. Spall strength, and deformation and damage modes of TiNb binary alloys depend on chemical compositions.

Microstructure, corrosion and anti-bacterial investigation of novel Ti-xNb-yCu alloy for biomedical implant application

Novel Ti-xNb-yCu alloys containing various Cu and Nb concentrations have been developed through heat treatment and rapid quenching. The effects of Cu and Nb content on microstructure, corrosion properties and bacterial inhibitory ability of the novel alloys have been systematically investigated with various characterisation methods. Results revealed that Ti3Cu alloy showed a typical eutectoid structure (α-Ti and Ti2Cu), Ti10Nb3Cu alloy exhibited three-phase coexistence microstructure (α+β+Ti2Cu), Ti30Nb alloy comprised of α+β phases, and Ti30Nb5Cu and Ti30Nb3Cu alloys comprised of single β phase. The corrosion behaviour of novel Ti-xNb-yCu alloys were studied in details using electrochemical measurements and immersion testing. It has been found that corrosion resistance of novel Ti-xNb-yCu alloys was improved with increasing Nb content, while the addition of Cu exhibited opposite trend on corrosion resistance. Higher Cu content (5%) in Ti30Nb alloy decreased its corrosion resistance while lower Cu content (3%) improved its corrosion resistance, probably due to the single-phase transition and less Cu-containing precipitates on the grain boundary of Ti30Nb3Cu. Besides, Cu-containing Ti alloys exhibited significantly better bacterial inhibitory properties. This study suggests that, Ti30Nb3Cu alloy with high corrosion resistance and excellent bacterial inhibitory property is promising for biomedical implant applications.

Mechanisms of near-linear elastic deformation behavior in a binary metastable β-type Ti-Nb alloy with large recoverable strain

A binary metastable β-type Ti-Nb alloy possessing large near-linear recoverable strain was designed to clarify the physical mechanisms responsible for high near-linear elastic deformability in near‑oxygen-free Ti-based alloys. The in situ synchrotron X-ray diffraction (SXRD) investigation reveals that in addition to the inherent elastic deformation, a reversible β↔α'' stress-induced martensitic transformation (SIMT) occurs during the near-linear elastic deformation. During the SIMT, the α'' martensitic variant 5 (V5) forms preferentially due to its maximum phase transformation strains among all 6 equivalent α'' variants. The orientation dependence of phase transformation strains of the preferential V5 leads to the appearance of different α'' diffraction peaks in the loading and Poisson’s directions during the SIMT, which is beneficial for accommodating the external macroscopic deformation to the great extent. Our experimental results show that the high near-linear elastic deformability of present Ti-Nb alloy is attributed to a combined effect of the large inherent elastic deformation arising from low Young's modulus as well as a reversible SIMT that covers a wide stress range and exhibits small phase transformation strains limited by the lattice constants of β and α'' phases. These results could provide a comprehensive understanding of the mechanisms responsible for huge near-linear elastic deformability of β-type titanium alloys.

Tribocorrosion-Resistant Ti40Nb-TiN Composites Having TiO2-Based Nanotubular Surfaces.

A novel multifunctional material was developed by hard TiN particle reinforcement addition to a β-type Ti40Nb alloy, followed by surface functionalization, yielding the formation of a nanotubular layer. Corrosion and tribocorrosion behaviors were investigated in a phosphate-buffered saline solution at body temperature. The results revealed that the Ti40Nb-TiN composites presented similar ipass and E(i=0) values together with relatively similar Rox and Cox. However, its tribocorrosion resistance drastically improved (wear volume is almost 15 times lower than an unreinforced alloy) as a consequence of the load-carrying effect given by the reinforcement phases. The corrosion and tribocorrosion behaviors were further improved through surface functionalization as observed by significantly lower ipass and higher Rox values and almost undetectable wear volume loss from tribocorrosion tests due to the formation of a well-adhered anatase-rutile TiO2-based nanotubular layer.

Spinodal decomposition coupled with a continuous crystal ordering in a titanium alloy

Spinodal decomposition mechanism is well-known for producing nanoscale modulated microstructure which is either sponge-like or plate-like. Our recent investigations of a Ti-Nb based titanium alloy have found two kinds of decomposition-induced transitions triggered simultaneously, a microstructural transition from the spongy-like to the plate-like and a crystal structure transition from bcc to hcp via the coupled atomic shear and shuffle mechanism along the Burgers pathway. Here focuses on thermal evolution kinetics of both transitions and their quantitative relations. Small angle neutron scattering profiles reveal that the aging treatments lead to a gradual change from an oval pattern to a butterfly pattern due to the spongy-to-plate microstructural transition. To characterize the crystal transition and its induced habit plane change, we define an ordering parameter from the shear component of the bcc-hcp transition. The results reveal that both follow the well-known power-law approximation with an activation energy of ∼209 kJ/mol, which is identical with diffusion energy of Nb in binary Ti-Nb alloy. However, their time exponential factors are different, about 1/5 for the microstructure growth and 1/16 for the crystal ordering and its induced habit plane change. The former is less than the common 1/3 law of the decomposition mechanism and the nucleation and growth mechanism. Aided by these kinetic equations, the microstructural and chemical parameters can be modeled by the crystal ordering. This provides a new strategy to tune the nanoscale microstructure by this novel spinodal decomposition coupled with a continuous crystal ordering.

Comparison of microstructure and mechanical behavior of Ti-35Nb manufactured by laser powder bed fusion from elemental powder mixture and prealloyed powder

Although different types of powder feedstock are used for additive manufacturing via laser powder bed fusion (L-PBF), limited work has attempted to directly compare the microstructure and mechanical behavior of components manufactured from those powder feedstock. This work investigated the microstructure, phase composition, melt pool morphology, and mechanical properties of a prealloyed Ti-35Nb alloy manufactured using L-PBF and compared these to their counterparts produced from elemental powder mixture. The samples manufactured from the powder mixture are composed of randomly distributed undissolved Nb in the α/β matrix, resulting from the unstable melt pool during the melting of the powder mixture. By contrast, parts produced from prealloyed powder display a homogeneous microstructure with β and α″ phases, owing to the full melting of prealloyed powder, therefore, a more stable melt pool to achieve a homogeneous microstructure. The Ti-35Nb manufactured from prealloyed powder exhibits large tensile ductility (about 10 times that of the counterparts using mixed powder), attributed to the high homogeneity in microstructure and chemical composition, strong interface bonding, relatively low oxygen content, and the existence of a large amount of β phase. This work sheds insights into understanding the effect of powder feedstock on the melt pool stability therefore the microstructure and mechanical behavior of the resultant parts.

Plasma electrolytic oxidation up to four-steps performed on niobium and Nb-Ti alloys

Plasma electrolytic oxidation (PEO) of up to four steps were performed on Niobium (Nb), and binary Niobium-Titanium alloys (Nbx-Ti, x = 50%, 90 wt.%), and the resulting oxidized surfaces were compared to their respective metallic substrate. The first and third steps were carried out in the phosphorus electrolyte, whereas the second and fourth steps were oxidized in the electrolyte containing calcium ions. Coatings formed from the second step were porous, with the chemical composition containing both calcium and phosphorus elements. The PEO process decreased the elastic moduli to approximately 60 GPa and increased the surface cell viability compared to the metallic surfaces without treatment. All surfaces produced from the second step-PEO demonstrated improved characteristics for application in metallic implants. Additionally, those performed on the alloys in electrolytes containing phosphate ions (up to three steps) exhibited greater performance on cytocompatibility tests.

Progress in Niobium Oxide-Containing Coatings for Biomedical Applications: A Critical Review.

Typically, pure niobium oxide coatings are deposited on metallic substrates, such as commercially pure Ti, Ti6Al4 V alloys, stainless steels, niobium, TiNb alloy, and Mg alloys using techniques such as sputter deposition, sol–gel deposition, anodizing, and wet plasma electrolytic oxidation. The relative advantages and limitations of these coating techniques are considered, with particular emphasis on biomedical applications. The properties of a wide range of pure and modified niobium oxide coatings are illustrated, including their thickness, morphology, microstructure, elemental composition, phase composition, surface roughness and hardness. The corrosion resistance, tribological characteristics and cell viability/proliferation of the coatings are illustrated using data from electrochemical, wear resistance and biological cell culture measurements. Critical R&D needs for the development of improved future niobium oxide coatings, in the laboratory and in practice, are highlighted.

Multi-Steps Magnetic Flux Entrance/Exit at Thermomagnetic Avalanches in the Plates of Hard Superconductors.

Avalanche cascades of magnetic flux have been detected at thermomagnetic instability of the critical state in the plates of Nb-Ti alloy. It was found that, the magnetic flux Φ enters conventional superconductor in screening regime and leaves in trapping regime in the form of a multistage “stairways”, with the structure dependent on the magnetic field strength and magnetic history, with approximately equal successive portions ΔΦ in temporal Φ(t) dependence, and with the width depending almost linearly on the plate thickness. The steady generation of cascades was observed for the full remagnetization cycle in the field of 2–4 T. The structure of inductive signal becomes complex already in the field of 0–2 T and it was shown, on the base of Fourier analysis, that, the avalanche flux dynamic produces, in this field range, multiple harmonics of the electric field. The physical reason of complex spectrum of the low-field avalanche dynamics can be associated with rough structure of moving flux front and with inhomogeneous relief of induction. It was established that the initiation of cascades occurs mainly in the central part of the lateral surface. The mechanism of cascades generation seems to be connected to the “resonator’s properties” of the plates.

Controlling the Young’s modulus of a ß-type Ti-Nb alloy via strong texturing by LPBF

The ß-type Ti-42Nb alloy was processed by laser powder bed fusion (LPBF) with an infrared top hat laser configuration aiming to control the Young’s modulus by creating an adapted crystallographic texture. Utilizing a top hat laser, a microstructure with a strong 〈0 0 1〉 texture parallel to the building direction and highly elongated grains was generated. This microstructure results in a strong anisotropy of the Young’s modulus that was modeled based on the single crystal elastic tensor and the experimental texture data. Tensile tests along selected loading directions were conducted to study the mechanical anisotropy and showed a good correlation with the modeled data. A Young’s modulus as low as 44 GPa was measured parallel to the building direction, which corresponds to a significant reduction of over 30% compared to the Young’s modulus of the Gaussian reference samples (67–69 GPa). At the same time a high 0.2% yield strength of 674 MPa was retained. The results reveal the high potential of LPBF processing utilizing a top hat laser configuration to fabricate patient-specific implants with an adapted low Young’s modulus along the main loading direction and a tailored mechanical biofunctionality.

Influence of Nb content on mechanical behavior and microstructure of Ti–Nb alloys

Abstract The effect of Nb content on the mechanical behavior of Ti-(20, 25, 30) at.% Nb alloys has been investigated. Results show that the storage modulus, the tensile strength and elongation at room temperature decrease with increasing Nb content. The Ti-20Nb and Ti-25Nb alloys show double-yielding behavior and they exhibit higher work hardening rate than the Ti-30Nb alloy. The Ti-20Nb alloy deforms by stress-induced β → α″ transformation and the reorientation of the α″ phase. While the Ti-25Nb alloy deforms by stress-induced martensitic transformation and deformation bands that are devoid of ω phase. The Ti-30Nb alloy, which has the highest β phase stability, deforms in a localized mode mainly by dislocation slip. The “marble-like” deformation microstructure previously reported in “gum metal” was observed in severely deformed Ti-25Nb and Ti-30Nb alloys.

Insights into the surface and biocompatibility aspects of laser shock peened Ti-22Nb alloy for orthopedic implant applications

This paper reports the effect of varying laser-peening fluences (3, 6 and 9 GW/cm2) on surface topography, oxide composition and wettability of low modulus Ti-22Nb at.% (Ti-35.4Nb wt.%) alloy with specific focus on the ensuing fretting wear and biocompatibility. Microtopography with nano-sized pores were generated during the laser interaction. LP-6 and LP-9 GW/cm2 surfaces displayed nano-porous distribution, with topographies characterized by negative skewness and platykurtosis. X-ray photoelectron studies revealed the development of mixed oxide layers rich in Ti4+ and Nb5+ when laser fluence was increased. Improved hydrophilic behavior was observed with increment in laser fluence displaying contact angles of 47.1° and 43.2° for LP-6 and LP-9 GW/cm2. Based on the preliminary surface characterizations, LP-6 and LP-9 GW/cm2 which displayed a platykurtic surface with negative skewness, Ti-Nb based mixed oxides and stable hydrophilic nature were selected for further analysis. Presence of Nb5+ ions rendered the oxide surfaces less defective, thereby improving fretting wear resistance. In particular, well-spread cells and up-regulation of beneficial genetic-markers (Ki67) on laser-peened surfaces demonstrated the role of nano-sized cues and oxide-layer in improving osseointegration aspects. Results demonstrate that LP-6 and LP-9 GW/cm2 surfaces on low modulus Ti-22Nb alloy can beneficially contribute towards the fretting wear and biocompatibility.

Effect of Nb Content and water quenching on microstructure and mechanical properties of Ti-Nb alloys fabricated by spark plasma sintering

ABSTRACT Titanium-niobium (Ti-Nb) alloys have been extensively studied for medical implants due to their advantageous mechanical properties and biocompatibility. However, the stress shielding effect remains a challenge. This research investigated the effects of Nb content and enhancement of α′′ formation on the mechanical properties of Ti-xNb alloys (x = 0, 5, 15 and 25%) fabricated by spark plasma sintering. Water quenching from the β phase induced α′′ phase formation in Ti-5Nb and Ti-15Nb samples, thereby reducing their Young’s modulus values but was not observed in commercially pure titanium (CP-Ti) and Ti-25Nb. Results showed that heat treatment with water quenching induced α′′ phase formation and can be used to tailor the properties of Ti-Nb alloys fabricated by SPS. This technique can also be used to enhance material ductility at high β-stabilizer content, as observed in Ti-25Nb samples.

Multi-principal element grain boundaries: Stabilizing nanocrystalline grains with thick amorphous complexions

Amorphous complexions have recently been demonstrated to simultaneously enhance the ductility and stability of certain nanocrystalline alloys. In this study, three quinary alloys (Cu–Zr–Hf–Mo–Nb, Cu–Zr–Hf–Nb–Ti, and Cu–Zr–Hf–Mo–W) are studied to test the hypothesis that increasing the chemical complexity of the grain boundaries will result in thicker amorphous complexions and further stabilize a nanocrystalline microstructure. Significant boundary segregation of Zr, Nb, and Ti is observed in the Cu–Zr–Hf–Nb–Ti alloy, which creates a quaternary interfacial composition that limits average grain size to 63 nm even after 1 week at ~ 97% of the melting temperature. This high level of thermal stability is attributed to the complex grain boundary chemistry and amorphous structure resulting from multi-component segregation. High-resolution transmission electron microscopy reveals that the increased chemical complexity of the grain boundary region in the Cu–Zr–Hf–Nb–Ti alloy results in an average amorphous complexion thickness of 2.44 nm, approximately 44% and 32% thicker than amorphous complexions previously observed in Cu–Zr and Cu–Zr–Hf alloys.Graphical abstract

Unusual strain relaxation mechanism in metastable [formula omitted] Ti-Nb alloy after rapid solidification

In this study, an unusual structural distortion in metastable β Ti-Nb was observed after laser melting. Selected area diffraction patterns (SADPs) from transmission electron microscopy (TEM) reveal that after rapid solidification from laser scans in a Ti-25Nb (at.%) sample, a difference in crystal structure was observed between the cellular solidification interior and the intercellular regions. While the intercellular regions remained the bcc (β) phase, the structure of the cell interior dis not match either β or the α’’ martensite. Instead, this structure can be interpreted either as an ordered orthorhombic structure with significantly different lattice parameters compared to α’’, or a distorted β with 8% strain along with one of the <100>β directions with selected variants of nanodomains which originate from the relaxation of interstitial oxygen atoms.

Study of the influence of titanium and niobium particle size on the Ti35Nb alloy production with controlled porosity

The present work is a continuation of the research carried out in a previous work, with the aim of improving the production of Ti35Nb alloy by reducing the particle size of Ti (from 50–149 Μm to < 53 Μm) and Nb (from 31–500 Μm to < 62 Μm) powders. Micro (MI) and Macroporous (MA) Ti35Nb alloy samples were processed by powder metallurgy. Ammonium bicarbonate (AB) was utilized as pore former additive for processing MA samples. The powders were mixed, uniaxially pressed and then sintered at 1300 ºC for 2 hours under argon atmosphere. The samples were characterized by SEM/EDS, XRD, profilometry, and Vickers hardness test. The porosity levels were determined by geometric method, Archimedes’ principle and quantitative metallographic analysis. The results showed that the processing parameters used in this work successfully produced porous Ti35Nb alloys with completely stabilized β-Ti phase, indicating an enhancement in the methodology when compared with those reported in previous work. Smaller particle sizes influenced positively on the chemical-physical properties of MI and MA samples, since they demonstrated an improvement in the their characteristics, such as: more homogeneous microstructure; better particle consolidation; homogeneous elemental distribution with no relevant chemical contamination; porosity values in accordance with literature; presence of low amounts of titanium oxides on the surfaces which can improve the biocompatibility features; suitable surface roughness parameters for bone implant applications and favouring adhesion of bioceramic coatings; more uniform microhardness values for both samples which make the material with a further predictable mechanical behavior.

Atomic –Scale Investigations of Passive Film Formation on Ti–Nb Alloys

Atomic –Scale Investigations of Passive Film Formation on Ti–Nb Alloys

Machinability of TiNb bio-compatible alloys

The success of biomedical implantation is linked to osseointegration, depending on the mechanical loading of the bone interface. The large difference in stiffness between the host bone (30 GPa) and the usual implant material (over 100 GPa), as well as the absence of mechanical stress at the surrounding bone, induce a stress shielding effect, which leads to bone atrophy and implant loss. A recent work has shown the possibility to produce so-called second-generation titanium alloys. β-type Ti alloys have been studied for biomedical applications, due to the composition of non-cytotoxic elements. Some TiNb alloys can reach after heat treatment a Young’s modulus close to 35 GPa, which is really close to bone’s one. Unfortunately, titanium and its alloys are well known for their poor machinability due to the hardness and low thermal conductivity. Machined surfaces of titanium alloys are also easily damaged (micro cracks, build-up edge, plastic deformation, heat-affected zones, and tension residual stresses) during the process. Studying process parameters is important to avoid these phenomena.The machinability of TiNb (turning, milling) has not been studied to date. Therefore, in this study, we examined the behavior of the TiNb titanium alloy for applications as a biomaterial in micro-cutting. Orthogonal cutting tests were performed on austenite and martensite states TiNb alloys and compared with Ti40 pure titanium. The aim was to evaluate the influence of the alloys and the cutting parameters on the evolution of the cutting forces, specific cutting energy, friction coefficient which are good indicators of machinability

Influence of Thermal Treatment of Ti–45Nb Alloy in Ultrafine-Grained State on Its Structural Parameters and Heat Capacity

Influence of Thermal Treatment of Ti–45Nb Alloy in Ultrafine-Grained State on Its Structural Parameters and Heat Capacity

Composition-Dependent Shuffle-Shear Coupling and Shuffle-Regulated Strain Glass Transition in Compositionally Modulated Ti-Nb Alloys

Composition-Dependent Shuffle-Shear Coupling and Shuffle-Regulated Strain Glass Transition in Compositionally Modulated Ti-Nb Alloys