Ti 29Nb 13Ta Research Articles

Anodization and nonstructural surface characterizations of fabricated Ti–29Nb–13Ta–7.1Zr alloy for biomedical applications and its mechanical, wettability, tribological, and corrosion properties

Implants subjected to tribocorrosion release metallic ions and solid wear debris, which can cause a peri-implant disease, bone loss, and eventually implant loosening. TiO2 coatings have a wide application range owing to their biocompatibility. In this study, the Ti–29Nb–13Ta–7.1 Zr alloy was fabricated using powder metallurgy technique. The samples were electrochemically oxidized to produce self-standing TiO2 nanotubular arrays followed by annealing for 1 h at 450 °C to improve their crystallinity. The prepared TiO2 coatings were characterized by SEM, X-ray diffraction, and EDX, and the wettability, tribomechanical characteristics, and corrosion behavior of bio-functionalized TiO2 nanotubes were investigated. Atomic force microscopy observations were conducted to examine wear scars, and the wear volume was measured via 2D profilometry. Microhardness and nanoindentation tests were performed to evaluate the mechanical characteristics of TiO2 nanotubes such as microhardness, nanohardness, and modulus of elasticity. The thickness and diameter of the observed TiO2 nanotubes are 2 μm and 90.94 nm, respectively. The obtained results revealed that the deposition of a biofunctionalized Ti/TiO2 nanotube layer enhanced the hydrophilicity, tribomechanical properties, and corrosion resistance of the Ti–29Nb–13Ta–7.1Zr alloy. The COF of Ti alloy was 0.51 and it decreased to 0.28 after anodization and annealing at 450 °C. The contact angle of the Ti sample was 79.9° and it decreased to 45.6° after annealing at 850 °C. However, after the anodic oxidation and annealing at 450 °C, the contact angle decreased to 45.6°.

In-vitro corrosion and surface properties of PVD-coated β-type TNTZ alloys for potential usage as biomaterials: Investigating the hardness, adhesion, and antibacterial properties of TiN, ZrN, and CrN film

In this study, the corrosion and surface properties of non-toxic and non-allergenic β-type Ti–29Nb–13Ta–4.6Zr alloys (TNTZ) coated with TiN, ZrN, and CrN layers using the PVD technique were investigated under in-vitro conditions. The coatings' hardness, adhesion resistance, and antibacterial properties were also studied, with a focus on their potential usage as biomaterials. The corrosion tests were conducted using potentiodynamic polarization, the hardness tests were conducted using the Knoop method, and the adhesion tests were conducted using pull-off tests. The wetting properties of the coatings were examined through contact angle and 3D morphological analysis. The coatings were characterized using SEM-EDS and XRD. The results showed that the adhesion resistance of all coatings was significantly higher than the expected adhesion strength for biomaterial coatings, while their corrosion resistance was higher compared to the uncoated alloy. Besides, the study demonstrates the potential of TiN, ZrN, and CrN coatings on β-type TNTZ for use as a biomaterial with desirable surface and antibacterial properties.

Concept and Fabrication of Beta-Type Titanium Alloy Rod with Parts Possessing Different Young’s Moduli for Spinal Fixation

This paper proposes the concept and fabrication process of titanium alloy rods for spinal fixation. A part of rod for fixing the lower side of the lumbar vertebra is strengthened, while the other part for fixing the upper side has low stiffness. The results obtained by finite element analysis reveal that a rod with partially lowered Young’s modulus has higher flexibility and fixity compared with a rod possessing high Young’s modulus throughout. Using Ti–29Nb–13Ta–4.6Zr alloys with oxygen contents of 0.2 and 0.4% as the model alloys, rods with partially different Young’s moduli were fabricated by aging treatment at 723 K, followed by partial heating up to above the β-transus temperature and quenching by high-frequency induction heating (IH-treatment). A single β-phase, which has low Young’s modulus, is obtained by IH-treatment and has lower strength. With regard to the as-aged parts, the precipitated condition of the α-phase can be changed by varying the aging time. The obtained Young’s modulus and strength reflect this change. Near the boundary between the as-aged and IH-treated parts, the hardness is gradually changed, and it is possible to gradually soften the material from the as-aged part to the IH-treated part.

Exceptional improvement in the wear resistance of biomedical β-type titanium alloy with the use of a biocompatible multilayer Si/DLC nanocomposite coating

A silicon/diamond-like carbon (Si/DLC) multilayer nanocomposite coating (MNC) was applied to the Ti–29Nb–13Ta‒4.6Zr (TNTZ) alloy to improve its wear resistance and durability. The Si/DLC MNC on the TNTZ alloy demonstrated an extremely low wear rate of 6.2 × 10−10 mm3N−1mm−1. Moreover, the wear track depth after one million wear cycles was found to be only 220 nm, while the thickness of the entire coating was 370 nm. Furthermore, cell culture tests demonstrated that the Si/DLC MNC samples exhibited better biocompatibility than the TNTZ alloy samples. A quantitative comparison of the cell adhesion behavior of the TNTZ and Si/DLC MNC samples indicated that 60% of the surface of the Si/DLC MNC sample was covered with cells, which was approximately twice the surface of the TNTZ alloy sample covered with cells. In addition, no dead cells were observed on the Si/DLC MNC samples, indicating that the Si/DLC MNC samples exhibited no toxic effects against the MC3T3 cells. These results indicate that the Si/DLC MNC enhances the wear resistance of the TNTZ alloy and improves its biofunctionality, thus making it a potential candidate for use in long-term implant applications.

Exfoliation Resistance, Microstructure, and Oxide Formation Mechanisms of the White Oxide Layer on CP Ti and Ti-Nb-Ta-Zr Alloys.

We found that specific biomedical Ti and its alloys, such as CP Ti, Ti–29Nb–13Ta–4.6Zr, and Ti–36Nb–2Ta–3Zr–0.3O, form a bright white oxide layer after a particular oxidation heat treatment. In this paper, the interfacial microstructure of the oxide layer on Ti–29Nb–13Ta–4.6Zr and the exfoliation resistance of commercially pure (CP) Ti, Ti–29Nb–13Ta–4.6Zr, and Ti–36Nb–2Ta–3Zr–0.3O were investigated. The alloys investigated were oxidized at 1273 or 1323 K for 0.3–3.6 ks in an air furnace. The exfoliation stress of the oxide layer was high in Ti–29Nb–13Ta–4.6Zr and Ti–36Nb–2Ta–3Zr–0.3O, and the maximum exfoliation stress was as high as 70 MPa, which is almost the same as the stress exhibited by epoxy adhesives, whereas the exfoliation stress of the oxide layer on CP Ti was less than 7 MPa, regardless of duration time. The nanoindentation hardness and frictional coefficients of the oxide layer on Ti–29Nb–13Ta–4.6Zr suggested that the oxide layer was hard and robust enough for artificial tooth coating. The cross-sectional transmission electron microscopic observations of the microstructure of oxidized Ti–29Nb–13Ta–4.6Zr revealed that a continuous oxide layer formed on the surface of the alloys. The Au marker method revealed that both in- and out-diffusion occur during oxidation in Ti–29Nb–13Ta–4.6Zr and Ti–36Nb–2Ta–3Zr–0.3O, whereas only out-diffusion governs oxidation in CP Ti. The obtained results indicate that the high exfoliation resistance of the oxide layer on Ti–29Nb–13Ta–4.6Zr and Ti-36Nb-2Ta-3Zr-0.3O are attributed to their dense microstructures composing of fine particles, and a composition-graded interfacial microstructure. On the basis of the results of our microstructural observations, the oxide formation mechanism of the Ti–Nb–Ta–Zr alloy is discussed.

The Ti3.6Nb1.0Ta0.2Zr0.2 coating on anodized aluminum by PVD: A potential candidate for short-time biomedical applications

In this study, Ti3.6Nb1.0Ta0.2Zr0.2 based coatings were deposited on anodized and non-anodized aluminum surfaces by PVD. For this purpose, a target for the magnetron sputtering PVD system was prepared from a β-type Ti–29Nb–13Ta–4.6Zr bulk alloy via hot-forgings. Surface morphologies and elemental composition analysis of the TNTZ-based PVD coatings were conducted using scanning electron microscopy attached with an energy dispersive spectroscopy incorporated (SEM-EDS). A micro-scratch and hardness tester was used to evaluate the adhesion and mechanical properties of the deposited coatings. The contact angle and electrochemical corrosion measurements were applied to assign the wettability levels and potential usability of the coated surfaces under in-vitro conditions. Also, the corrosion resistance of the coatings was compared with commercial Ti and Ti6Al4V alloys. The results showed that the coated surfaces were exhibited a hydrophilic behavior and adequate in-vitro resistance in simulated body fluids (SBF). Besides, the TNTZ coatings on anodized surfaces were presented different cracking mechanisms and higher adhesion resistance than that of their non-anodized surfaces. The reason for the behavior has been discussed in the present study.

Influence of oxygen addition and aging on the microstructure and mechanical properties of a β-Ti-29Nb–13Ta–4Mo alloy

In this work, theoretical composition design and thermo-mechanical treatments were combined in order to improve the mechanical compatibility of a metastable β-type Ti–29Nb–13Ta–4Mo (wt%) alloy. Also, the influence of Mo and O alloying elements were investigated. By applying cold rolling and low temperature aging (673K during 20 and 100 min) different behaviours in microstructure and mechanical properties were identified. Alloys with Ultimate Tensile strength-UTS = 854 MPa and Elastic Modulus = 65 GPa were successfully fabricated. The microstructure responsible for that behaviour consisted mainly of β-matrix and ω-precipitation obtained via cold rolling plus short-time aging at low temperature, i.e. 673K for 20 min. These precipitates increase the strength of the material by hindering the motion of dislocations while the β-matrix with relatively high content of β-stabilizers (such, Mo) gives rise to the observed low elastic modulus. By extending aging time (100 min), a higher UTS is reached, but a slight increase in Elastic Modulus is also observed. The addition of oxygen increased mechanical and physical properties by favouring ω-phase formation. Whereas, Mo content increased β-stability, and in solution treated condition, only β-phase could be observed.

Effect of Potential and Microstructure on the Tribocorrosion Behaviour of Beta and Near Beta Ti Alloys I

Current hip prostheses make extensive use of Ti-6Al-4 V alloy. This material was originally designed for aerospace applications. Moreover, its poor tribological properties are well known. However, beta, or near beta Ti alloys are known to have superior properties in that its elastic modulus is closer to that of bone coupled with a good fatigue resistance. Therefore, this work aims to analyse the tribocorrosion behaviour of 4 different titanium alloys (Ti-13Nb-13Zr, Ti-12Mo-6Zr-2Fe and Ti–29Nb–13Ta–4.6Zr aged at 300 °C and at 400 °C) at anodic potential, OCP and cathodic potential at 0.5 N, 1 N and 2 N in bovine serum to identify the main cause of material degradation, effect of microstructure and the synergism between corrosion and wear. The results show the alloys become more active when subjected to sliding in all conditions, but the material loss is lower at anodic potential. Finally, at anodic potential wear is lower than at cathodic potential which is explained by increase in the mechanical wear at cathodic potential.

Influence of the deformation rate on phase stability and mechanical properties of a Ti–29Nb–13Ta–4.6Zr–xO alloy analyzed byin situhigh-energy X-ray diffraction during compression tests

Abstract

Effect of Nb addition on high-temperature oxidation behavior, oxide layer structure, and its exfoliation resistance of Ti-Nb Alloys

The authors proposed an oxide coating on Ti alloys for the dental abutment tooth, and they had reported that Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy forms a dense oxide layer by high-temperature oxidation. On the other hand, CP Ti forms a multilayered oxide consisted of rutile monolayers and the void layer. This morphological change by alloying is supposed to be mainly caused by Nb addition in Ti since the dense oxide layer of TNTZ mainly consists of rutile TiO2and TiNb2O7.Therefore, in this study, oxidation behaviors of various range of Nb content of Ti-xNb alloys (x = 1 ~ 32 mol%) were investigated, and exfoliation resistance was evaluated. And in this paper, the oxide/metal interfacial microstructure of oxidized CP Ti, TNTZ alloy, and Ti-Nb alloy was studied by a transmission electron microscopy (TEM) and by a scanning transmission electron microscopy with an electron dispersive spectroscopy (STEM-EDS).The cross-sectional observations suggested that the substrate was gradually oxidized during heat treatment, and nucleation and grain growth of TiO2and TiNb2O7proceed at the metal/oxide interface. Consequently, the gradual oxidation process in TNTZ and Ti-Nb alloys could lead to its continuous interfacial microstructure and dense oxide structure, which can achieve high exfoliation resistance.

Compressive Mechanical Properties and Shock-Induced Reaction Behavior of a Ti–29Nb–13Ta–4.6Zr Alloy

The compressive mechanical properties of a Ti–29Nb–13Ta–4.6Zr alloy were investigated at room temperature under various strain rates. The parameters of a modified Johnson–Cook constitutive equation were determined to describe the strain softening behavior under dynamic conditions. The testing results under compression show yield strength evidently increases with the increase of the strain rate. Moreover, it was found that the strain-rate effect of the yield strength upon dynamic deformation is more significant than that upon quasi-static deformation. In order to characterize the impact-initiated reaction behavior of Ti–29Nb–13Ta–4.6Zr alloy, the quasi-sealed test chamber was used to measure the pressure caused by energy released of fragments. It was obviously shown that the exothermic chemical reaction was more intense with the increase of impact velocity.

Low Springback and Low Young’s Modulus in Ti–29Nb–13Ta–4.6Zr Alloy Modified by Mo Addition

Low Springback and Low Young’s Modulus in Ti–29Nb–13Ta–4.6Zr Alloy Modified by Mo Addition

Formation of a hydroxyapatite layer on Ti–29Nb–13Ta–4.6Zr and enhancement of four-point bending fatigue characteristics by fine particle peening

A hydroxyapatite (HAp) surface layer was generated at room temperature on a beta-titanium alloy (Ti-29Nb-13Ta-4.6Zr, TNTZ) using fine particle peening (FPP), as a means of enhancing fatigue resistance. This material is commonly employed in bio-implants, but has a suboptimal Young's modulus. Treated specimens were assessed using scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and electron backscatter diffraction, as well as by measuring the Vickers hardness. Performing FPP using shot particles made of HAp was found to transfer the particles to the TNTZ surface to rapidly produce a HAp layer that became thicker as the FPP process progressed. Room-temperature four-point bending fatigue tests in air showed that the HAp layer resulting from the FPP process increased the endurance limit of test specimens. This improved performance is ascribed to the appearance of a hardened surface layer having a significant degree of compressive residual stress.

The plasma electrolytic oxidation (PEO) coatings to enhance in-vitro corrosion resistance of Ti–29Nb–13Ta–4.6Zr alloys: The combined effect of duty cycle and the deposition frequency

In this study, the TiO2-matrix coatings including hydroxyapatite (HA) and tricalcium phosphate (TCP) were successfully deposited on the β-type Ti–29Nb–13Ta–4.6Zr alloys by plasma electrolytic oxidation (PEO) process to enhance the in-vitro corrosion resistance of the alloys. An electrolyte containing calcium hydroxide (CaOH) and sodium phosphate dodecahydrate (Na3PO4·12H2O) were used to prepare micro-arc oxidized samples. The effect of duty cycle, deposition frequency, coating thickness, and surface morphologies have been discussed in the view of corrosion phenomena. The coated morphologies were characterized with scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). The corrosion behaviors of the coatings were investigated using potentiodynamic polarization scanning (PDS) technique in Ringer's solutions at body temperature. In addition, the immersion tests on the coated and uncoated samples were performed to observe the apatite phase formation on the surface. X-ray diffraction technique (XRD) has been used in order to determination Ca- and P-based phases on the surfaces. It was found that the corrosion rates of the all coated samples were approximately 4–14 times lower than the uncoated TNTZ sample. The highest resistant coating to corrosion was obtained in the oxidized TNTZ samples deposited at 500 Hz with 30% duty cycle by PEO.

Synthesis of biphasic calcium phosphate (BCP) coatings on β‒type titanium alloys reinforced with rutile-TiO2 compounds: adhesion resistance and in-vitro corrosion

In this study, β type Ti‒29Nb‒13Ta‒4.6Zr alloys coated with biphasic calcium phosphate (BCP) reinforced with rutile-TiO2 compounds by sol-gel technique to evaluate its possible usage in biomaterial science. Calcium nitrate tetrahydrate (Ca(NO3)2∙4H2O), di-ammonium hydrogen phosphate (NH4)2HPO4), ammonium hydroxide (NH4OH), and titanium (IV) propoxide (Ti(OC3H7)4) (Merck, Germany) were used as precursors for producing the BCP-only and BCP/TiO2 composite coatings. Synthesis and coating procedure, surface morphology, adhesion strength, and corrosion results of the coated samples have been investigated in details. XRD technique has been used in order to characterization of BCP phases. The morphological observations of coatings were determined by using a scanning electron microscopy (SEM). In-vitro corrosion behaviors of the coatings have been determined with polarization method in Ringer’s electrolyte at body temperature. It was found that the BCP/TiO2 coating synthesized on TNTZ alloy has higher scratch resistance than BCP-only coating due to its containing rutile-TiO2 compounds. In addition, it can be said that the BCP/TiO2 coated sample was less susceptibility to corrosion than the BCP-only coatings and uncoated TNTZ sample in simulated body fluid.

Electrochemical Corrosion Behaviour of Ti–29Nb–13Ta–4.6Zr Alloy in Physiological Solution Containing Various Synovial Joint Lubricants

Ti alloys are well known for their biocompatibility and high specific strength. In the present work, the electrochemical behaviour of Ti–13Ta–29Nb–4.6Zr alloy having β structure in Hank’s solution containing various joint lubricants has been studied. The results show that Ti–13Ta–29Nb–4.6Zr alloy is a potential biomaterial for joint applications. The electrochemical behaviour of Ti–13Ta–29Nb–4.6Zr alloy is not influenced significantly by the nature of lubrication. The highest corrosion rate of investigated alloy is around 1.2 mm/year in Hyaluronic Acid containing Hank’s solution. The growth of passive layer is the slowest and the passive layer is the most porous in Hank’s solution containing hyaluronic acid.

Significant improvement in cell adhesion and wear resistance of biomedical β-type titanium alloy through ultrasonic nanocrystal surface modification

A novel β-type Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy with a low Young's modulus, high bio-corrosion resistance, and excellent biocompatibility has been recently introduced for implant applications. Here, ultrasonic nanocrystal surface modification (UNSM) treatment was applied to TNTZ alloy to improve its wear resistance and biofunctionality. Application of UNSM to a TNTZ alloy resulted in the generation of a nanostructured surface layer. The wear resistance of the UNSM-treated specimen was observed to be more than 7 times higher than that of the untreated one. Cell culture tests indicated that MC3T3 cells adhered and spread more readily on the UNSM-treated specimen than on the untreated one. MTT assays after 1 and 4 days in culture also indicated enhancement of cell proliferation on the UNSM-treated specimen than that of the untreated one. Live/dead assay revealed no significant cytotoxicity in either substrate. The significant improvement of cell adhesion, spreading, and proliferation on the UNSM-treated TNTZ alloy specimen were attributed to both grain refinement and micro-patterned surface effects. These results demonstrate that UNSM-treatment not only improves the wear resistance of TNTZ alloy, but also enhances its biocompatibility, which makes it a strong candidate for applications in medical implants.

Effects of shot-peening and atmospheric-pressure plasma on aesthetic improvement of Ti–Nb–Ta–Zr alloy for dental applications

Ti and Ti alloys are widely used for biomedical applications such as artificial joints and dental devices because of their good mechanical properties and biochemical compatibility. However, dental devices made of Ti and Ti alloys do not have the same color as teeth, so they are inferior to ceramics and polymers in terms of aesthetic properties. In a previous study, Ti–29Nb–13Ta–4.6Zr was coated with a white Ti oxide layer by heat treatment to improve its aesthetic properties. Shot-peening is a severe plastic deformation process and can introduce a large shear strain on the peened surface. In this study, the effects of shot-peening and atmospheric-pressure plasma on Ti–29Nb–13Ta–4.6Zr were investigated to form a white layer on the surface for dental applications.

Experimental clarification of the cyclic deformation mechanisms of β-type Ti–Nb–Ta–Zr-alloy single crystals developed for the single-crystalline implant

Quaternary Ti–Nb–Ta–Zr (TNTZ) type β-Ti alloys with a body-centered cubic (bcc) structure have been of great interest as new implant biomaterials for bone replacement. Recently, we have proposed a “single crystalline β-Ti implant” as a novel hard-tissue replacement to suppress the stress shielding to bone after healing. To develop this, the fatigue properties and its controlling mechanisms of the TNTZ single crystals must be clarified. In this study, we focused on three alloys: Ti–25Nb–10Ta–5Zr(25Nb), Ti–29Nb–13Ta–4.6Zr(29Nb), and Ti–35Nb–10Ta–5Zr(35Nb) (mass%), and the cyclic deformation behaviors were examined using their single crystals. The shapes of the hysteresis loops were significantly different for these alloys, which was ascribed to the operation of different deformation modes: stress-induced α”-martensite (α”-SIM), {332}<113> twinning, and {101}<111> slip in the 25Nb, 29Nb, and 35Nb alloys, respectively. The hysteresis loops during cyclic deformation exhibited very irregular shapes for 25Nb and 29Nb, accompanied by a flow-stress asymmetry in tension and compression. This was caused by the polarized feature on the formation of them in tension and compression. In addition, the apparent yield stress in a hysteresis loop greatly decreased after the second cycle, owing to the reversible motion of the interfaces of the SIM and {332} twins by altering the direction of the applied stress. Although the cyclic deformation behavior was controlled by a similar mechanism in them, 29Nb was found to exhibit a much shorter fatigue life than 25Nb. This is because of the difference in the decreasing tendency of the reversibility for the SIM and {332} twins as cyclic deformation proceeded. The obtained results demonstrate that the controls of their asymmetric features and the reversible motion are the important factors to develop these alloys as a practical “single crystalline β-Ti implant”.

Biomedical titanium alloys with Young's moduli close to that of cortical bone.

Biomedical titanium alloys with Young’s moduli close to that of cortical bone, i.e., low Young’s modulus titanium alloys, are receiving extensive attentions because of their potential in preventing stress shielding, which usually leads to bone resorption and poor bone remodeling, when implants made of their alloys are used. They are generally β-type titanium alloys composed of non-toxic and allergy-free elements such as Ti–29Nb–13Ta–4.6Zr referred to as TNTZ, which is highly expected to be used as a biomaterial for implants replacing failed hard tissue. Furthermore, to satisfy the demands from both patients and surgeons, i.e., a low Young’s modulus of the whole implant and a high Young’s modulus of the deformed part of implant, titanium alloys with changeable Young’s modulus, which are also β-type titanium alloys, for instance Ti–12Cr, have been developed. In this review article, by focusing on TNTZ and Ti–12Cr, the biological and mechanical properties of the titanium alloys with low Young’s modulus and changeable Young’s modulus are described. In addition, the titanium alloys with shape memory and superelastic properties were briefly addressed. Surface modifications for tailoring the biological and anti-wear/corrosion performances of the alloys have also been briefly introduced.