Ti-29Nb-13Ta-4.6Zr Research Articles

Effect of interference laser treatment on the surface region homogeneity of a biomedical [formula omitted]-Ti alloy

This study provides a detailed insight into the microstructure and chemical composition of a surface region of a novel, metastable Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy with a low Young’s modulus modified by Direct Laser Interference Patterning (DLIP) using an Nd:YAG (1064 nm) with 10 ns pulse duration. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy, and Scanning Transmission Electron Microscopy (STEM) were employed to investigate the microstructure of the cross-section of modified TNTZ. For chemical composition analysis of the surface region, X-ray Photoelectron Spectroscopy (XPS) and Atom Probe Tomography (APT) were applied. The chemical composition analysis was divided into two stages: surface analysis (XPS and APT) and analysis of a bulk (APT at the depth of 300 nm). Through the interference phenomenon during DLIP treatment, we observed significant microstructure evolution in the surface region of TNTZ alloy — grain refinement on the tops of the grooves while the microstructure at the bottoms was unattached. APT measurements at the depth of 300 nm revealed a noticeable local chemical heterogeneity of the substrate alloy, that has not been considered before when designing the metastable β-Ti systems. The applied laser treatment homogenizes the remelted zones and thus provides an additional factor influencing the surface properties.

Improving the Corrosion Resistance of TNTZ in Hanks’ Solution after Thermomechanical Treatment

Ti-29Nb-13Ta-4.6Zr (TNTZ) is a new titanium alloy potentially to be used as bone implant material because of its advantages in terms of strength, ductility, non-toxicity, corrosion resistance, and biocompatibility. Its mechanical properties are suitable for bone applications; however, there are still problems related to its corrosion behavior when used for a long time. Therefore, this research aims to determine the corrosion rate and types, and provide corrosion prevention by applying the thermomechanical treatment on TNTZ in Hanks’ solution. The limitation of this research was in not conducting the TNTZ biocompatibility tests. This research was conducted using the potentiodynamic polarization method in Hanks’ solution as the corrosive medium at a temperature of 37°C and a pH of 6.8. Before corrosion testing, a TNTZ sample was treated with thermomechanical treatment combined with solution treatment at a temperature of 850°C and a holding time of 45 minutes, followed by rapid cooling (water quenching), and plastic deformation with deformation variations of 10%, 15%, and 20%, and it was ended with aging heat treatment at a temperature of 300°C and holding time for 1 hour. The novelties of this research are the valid data of corrosion rate and type of TNTZ, which were unavailable before, and corrosion prevention through thermomechanical treatment of TNTZ in Hanks’ solution. The thermomechanical treatment is proved to reduce the pitting corrosion in TNTZ. The results show that thermomechanical treatment and increased plastic deformation can reduce the value of the corrosion rate, as evidenced by the pre-thermomechanical and thermomechanical TNTZ corrosion rates with deformation variations of 10%, 15%, and 20%, respectively, which were 5.522 x 10-4 mmpy; 2.754 x 10-4 mmpy; 2.290 x 10-4 mmpy; and 2.064 x 10-4 mmpy, respectively. TNTZ, after thermomechanical treatment, had the lowest corrosion rate, i.e., 2.064 x 10-4 mmpy, while Ti-6Al-7Nb had the highest one, i.e., 3.05 x10-2 mmpy. The type of TNTZ corrosion is pitting corrosion, as shown by the loss of zirconium that reduced the volume, causing pits to occur. Meanwhile, after thermomechanical treatment, pitting corrosion happened on TNTZ because of the loss or release of zirconium. This research shows that after thermomechanical treatment, TNTZ is the best material compared to other materials for biomedical applications based on corrosion resistance.

Structure, Properties, and Corrosion Behavior of Ti-Rich TiZrNbTa Medium-Entropy Alloys with β+α″+α' for Biomedical Application.

Five Ti-rich β+α″+α' Ti-Zr-Nb-Ta biomedical medium-entropy alloys with excellent mechanical properties and corrosion resistance were developed by considering thermodynamic parameters and using the valence electron concentration formula. The results of this study demonstrated that the traditional valence electron concentration formula for predicting phases is not entirely applicable to medium-entropy alloys. All solution-treated samples with homogeneous compositions were obtained at a low temperature (900 °C) and within a short period (20 min). All solution-treated samples exhibited low elastic moduli ranging from 49 to 57 GPa, which were significantly lower than those of high-entropy alloys with β phase. Solution-treated Ti65-Zr29-Nb3-Ta3 exhibited an ultra-high bending strength (1102 MPa), an elastic recovery angle (>30°), and an ultra-low elastic modulus (49 GPa), which are attributed to its α″ volume fraction as high as more than 60%. The pitting potentials of all samples were higher than 1.8 V, and their corrosion current densities were lower than 10-5 A/cm3 in artificially simulated body fluid at 37 °C. The surface oxide layers on Ti65-Zr29-Nb3-Ta3 comprised TiO2, ZrO2, Nb2O5, and Ta2O5 (as discovered through X-ray photoelectron spectroscopy) and provided the alloy with excellent corrosion and pitting resistance.

Effect of scanning strategy on microstructure and mechanical properties of a biocompatible Ti–35Nb–7Zr–5Ta alloy processed by laser-powder bed fusion

The influence of scanning strategy (SS) on microstructure and mechanical properties of a Ti–35Nb–7Zr–5Ta alloy processed by laser-powder bed fusion (L-PBF) is investigated for the first time. Three SSs are considered: unidirectional-Y; bi-directional with 79° rotation (R79); and chessboard (CHB). The SSs affect the type and distribution of pores. The highest relative densities and more homogeneous distribution of pores are obtained with R79 and CHB scanning strategies, whereas aligned pores are formed in the unidirectional-Y. The SSs show direct influence on the crystallographic texture with unidirectional-Y strategy showing fiber texture. The R79 strategy results in a weak texture and the CHB scanning strategy forms a randomly oriented heterogeneous grain structure. The lowest Young modulus is obtained with the unidirectional-Y strategy, whereas the R79 strategy results in the highest yield strength. It is shown that the SSs may be used for tuning the microstructure of a beta-Ti alloy in L-PBF. Graphical abstract

A novel Ti42.5Zr42.5Nb5Ta10 multi-principal element alloy with excellent properties for biomedical applications

Body-centered cubic (BCC) Ti–Zr–Nb–Ta multi-principal element alloys (MPEAs) have drawn extensive research attention as orthopedic implant materials. In this work, a novel Ti42.5Zr42.5Nb5Ta10 multi-principal element alloy was developed for biomedical applications in terms of its microstructure, mechanical properties, wear performance, corrosion behavior, and in vitro biocompatibility. The Ti42.5Zr42.5Nb5Ta10 alloy after cold rolling followed by annealing at 880 °C (TZNT-880), possessed excellent mechanical properties combination, with a yield strength of 839.5 MPa, elongation at fracture of 22.6%, and Young's modulus of 63.2 GPa, superior to most of the currently existing biomedical BCC MPEAs. Meanwhile, TZNT-880 alloy exhibited higher wear resistance compared with commercial CP-Ti and Ti6Al4V, which is strongly related to its high H/E and H3/E2 values. Also, TZNT-880 alloy showed good corrosion resistance, as revealed by a nobler corrosion potential, lower corrosion current densities, and higher passivation stability, which is attributed to the formation of passivation films consisting of TiO2, ZrO2, Nb2O5, and Ta2O5. The in vitro biocompatibility tests demonstrated that the TiZrNbTa alloys can support cell adhesion and proliferation with high biocompatibility comparable to that of CP-Ti and Ti6Al4V, indicating their potential as a candidate for implant material.

Effect of Alloying Elements on the Compressive Mechanical Properties of Biomedical Titanium Alloys: A Systematic Review.

Due to problems such as the stress-shielding effect, strength–ductility trade-off dilemma, and use of rare-earth, expensive elements with high melting points in Ti alloys, the need for the design of new Ti alloys for biomedical applications has emerged. This article reports the effect of various alloying elements on the compressive mechanical performance of Ti alloys for biomedical applications for the first time as a systematic review following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines on this subject. The search strategy in this systematic review used Scopus, Web of Science, and PubMed databases and searched the articles using (Beta-type OR β) AND Titanium AND (Mechanical property OR Microstructure) AND Alloying element keywords. Original articles from 2016 to 2022 published in English have been selected for this study as per the inclusion criteria. The results have shown that Nb can be used as the primary alloying element with Ti as it is a strong β-stabilizer element which also reduces the elastic modulus of Ti alloys. The β-eutectic elements (Fe, Cr, and Mn) have also emerged as cost-effective alloying elements that could improve the mechanical performance of Ti alloys. Ti–Nb–Zr–Ta alloyed with Si has shown potential to withstand the strength–ductility trade-off dilemma. The combination of a Ti–Nb binary alloy has emerged as an attractive material for designing low elastic modulus Ti alloys. The mechanical performance of the Ti–Nb alloy can be further improved using the β-eutectic (Fe, Cr, and Mn) and neutral (Zr, Sn) elements to be alloyed with a Ti–Nb binary alloy. The strength–ductility trade-off issue can be overcome using Si as an alloying element in Ti–Nb–Zr–Ta alloys.

Microstructure and mechanical properties evolution during thermomechanical processing of a Ti–Nb–Zr–Ta–Sn–Fe alloy

During the last decades, Titanium-based alloys have shown a suitable combination of strength, ductility, corrosion and biocompatibility properties, that marks them as suitable implant materials for biomedical applications. In this study, a Ti–30Nb–12Zr–5Ta–2Sn-1.25Fe (wt%) alloy was produced by melting in a cold crucible induction in levitation furnace, deformed by cold rolling, with a total deformation degree (thickness reduction) of 50%, in five equal steps, and solution treated at 850 °C, with progressive treatment durations, from 5min to 20min, in 5min increments. The initial microstructure is homogenous, consisting of equiaxed β-Ti phase grains showing an average grain size close to 135 μm. The applied cold deformation induces changes in the microstructure, which shows the presence of deformation bands, twins, dislocation bands and of an increased crystal defects density and residual strain–stress fields. Also, an increase in strength and decrease in ductility properties are noticed due to the strain hardening. The applied solution treatment leads to the regeneration of the microstructure, the obtained microstructure showing homogeneous equiaxed β-Ti phase grains, with an average grain size between 60 μm and 80 μm, depending on the solution treatment duration. Also, a decrease in strength and increase in ductility properties are noticed due to the lowering of the crystal defects density, remanent strain–stress fields and an increase of the average grain size.

Proliferation of osteoblast precursor cells on the surface of TiO2 nanowires anodically grown on a β-type biomedical titanium alloy

Studies have shown that anodically grown TiO2 nanotubes (TNTs) exhibit excellent biocompatibility. However, TiO2 nanowires (TNWs) have received less attention. The objective of this study was to investigate the proliferation of osteoblast precursor cells on the surfaces of TNWs grown by electrochemical anodization of a Ti-35Nb-7Zr-5Ta (TNZT) alloy. TNT and flat TNZT surfaces were used as control samples. MC3T3-E1 cells were cultured on the surfaces of the samples for up to 5 days, and cell viability and proliferation were investigated using fluorescence microscopy, colorimetric assay, and scanning electron microscopy. The results showed lower cell proliferation rates on the TNW surface compared to control samples without significant differences in cell survival among experimental conditions. Contact angles measurements showed a good level of hydrophilicity for the TNWs, however, their relatively thin diameter and their high density may have affected cell proliferation. Although more research is necessary to understand all the parameters affecting biocompatibility, these TiO2 nanostructures may represent promising tools for the treatment of bone defects and regeneration of bone tissue, among other applications.

Formation of coherent BCC/B2 microstructure and mechanical properties of Al–Ti–Zr–Nb–Ta–Cr/Mo light-weight refractory high-entropy alloys

Formation of coherent BCC/B2 microstructure and mechanical properties of Al–Ti–Zr–Nb–Ta–Cr/Mo light-weight refractory high-entropy alloys

Study of Electrochemical and Biological Characteristics of As-Cast Ti-Nb-Zr-Ta System Based on Its Microstructure

The quaternary Ti-Nb-Zr-Ta (TNZT) alloy was successfully cast-fabricated with the objective to be used in the medical field. Samples’ microstructure was compared to CP-Ti and Ti-6Al-4V (control samples) and related to corrosion, ion release and biological properties. As-cast TNZT was formed with large β grain sizes (285 µm) compared to the ultrafine α grain sizes of CP-Ti (11 µm) and the α + β ultrafine grain sizes of 1.45 µm and 0.74 µm. Hardness and flexural elastic moduli (94 HV and 43 GPa) came close to the biological structures, such as dentin and enamel values. The ion release mechanism of as-cast TNZT was significantly lesser than CP-Ti and Ti-6Al-4V, which can be related to the difference in samples’ grain sizes and chemical compositions. However, the corrosion rate was higher than for the control samples; this way offers corrosion properties inferior with respect to the properties obtained in the reference materials. Biological assays demonstrated that the two-cell (hDPSCs and MG-63) lineage studied presented good adhesion and capability to differentiate in bone cells on the as-cast TNZT surface, and no cytotoxicity effects were found. Details and reasons based on samples’ microstructure are discussed.

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.

Circumventing the strength–ductility trade-off of β-type titanium alloys by defect engineering during laser powder bed fusion

In this study, we propose a novel defect engineering strategy for circumventing the strength–ductility trade-off of a β-type Ti–35Nb–7Zr–5Ta alloy and discuss its underlying mechanism. This strategy is based on the simultaneous introduction of dislocations and twins into the alloy structure through the thermal stress generated during additive manufacturing via laser powder bed fusion (LPBF). As a result, the LPBF-fabricated alloy contains high-density dislocations and two different types of nanosized {112}〈111〉 mechanical twins: unique zigzag-shaped and conventional lamellar ones. Interestingly, the produced alloy exhibits a high tensile yield strength of 816 MPa and large elongation of 16.5%, which significantly exceed the published values for other representative β-type titanium alloys fabricated by various material processing methods. Such a high yield strength is predominantly attributed to the introduced defects, and the relative contributions of dislocation strengthening and twin strengthening are equal to 58.0% and 26.1%, respectively. Meanwhile, the large elongation results from the inhibition effect of the produced twins on the dislocation motion as well as from their dislocation pass-through and growth. The obtained results can provide guidelines for the microstructural design and fabrication of novel β-type titanium alloys with excellent mechanical properties by defect engineering during additive manufacturing.

Laser Powder Bed Fusion Additive Manufacturing of a Low-Modulus Ti-35Nb-7Zr-5Ta Alloy for Orthopedic Applications.

Laser powder bed fusion (L-PBF) was attempted here to additively manufacture a new generation orthopedic β titanium alloy Ti–35Nb–7Zr–5Ta toward engineering patient-specific implants. Parts were fabricated using four different values of energy density (ED) input ranging from 46.6 to 54.8 J/mm3 through predefined laser beam parameters from prealloyed powders. All the conditions yielded parts of >98.5% of theoretical density. X-ray microcomputed tomography analyses of the fabricated parts revealed minimal imperfections with enhanced densification at a higher ED input. X-ray diffraction analysis indicated a marginally larger d-spacing and tensile residual stress at the highest ED input that is ascribed to the steeper temperature gradients. Cellular to columnar dendritic transformation was observed at the highest ED along with an increase in the size of the solidified features indicating the synergetic effects of the temperature gradient and solidification growth rate. Density measurements indicated ≈99.5% theoretical density achieved for an ED of 50.0 J/mm3. The maximum tensile strength of ≈660 MPa was obtained at an ED of 54.8 J/mm3 through the formation of the columnar dendritic substructure. High ductility ranging from 25 to 30% was observed in all the fabricated parts irrespective of ED. The assessment of cytocompatibility in vitro indicated good attachment and proliferation of osteoblasts on the fabricated samples that were similar to the cell response on commercially pure titanium, confirming the potential of the additively manufactured Ti–35Nb–7Zr–5Ta as a suitable material for biomedical applications. Taken together, these results demonstrate the feasibility of L-PBF of Ti–35Nb–7Zr–5Ta for potentially engineering patient-specific orthopedic implants.

Electrochemical corrosion behavior of Ti–35Nb–7Zr–5Ta powder metallurgic alloys after Hot Isostatic Process in fluorinated artificial saliva

The present study aimed to evaluate the effect of the Hot Isostatic Process (HIP) process on the microstructure, phase stability and corrosion resistance of Ti35Nb7Zr5Ta powder metallurgy alloys. The corrosion resistance of titanium alloys was tested by analyzing the open circuit potential (OCP), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and ion release in physiological Fusayama solution. Polarization curves showed that the Ti–35Nb–7Zr–2Ta alloy presented good passivation behavior thanks to its low current densities (<10−8 A/cm2) and high polarization resistance. The interpretation of an equivalent electric circuit (EEC) demonstrated the formation of a very stable oxide film on the alloy, as indicated by good capacitive behavior, high impedance values (>106 Ω cm2) at low frequencies and phase angles close to −90° according to the EIS results with less ion release.

The influence of the Nb:Ta ratio on the microstructural evolution in refractory metal superalloy systems

Refractory metal superalloys have the potential to facilitate a significant increase in gas turbine operating temperatures that would enhance efficiency and reduce emissions. However, fulfilling this potential requires a much more detailed understanding of the underlying metallurgy and how it is influenced by alloying additions. Here, the influence of systematically varying the Nb:Ta ratio in a series of Ti–Zr–Nb–Ta alloys has been studied and compared to thermodynamic predictions. The experimental results show that higher Nb:Ta ratios suppress phase separation but lower the inter-phase misfit. As such, optimizing these alloys for specific applications will require careful balancing of these effects.

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.

Influence of oxygen and plastic deformation on the microstructure and the hardness of a Ti–Nb–Ta–Zr–O Gum Metal

In this paper, the Gum Metal Ti–29Nb–13Ta-4.6Zr-xO with two different oxygen contents (2200 and 4600 ppm) was prepared by high-pressure torsion (HPT) and their microstructural evolution, thermal stability, physical and mechanical properties were investigated for specimens prepared under different processing conditions. An increase in the β-phase stability at the expense of αʺ, as well as in the hardness was observed with the combined effect of oxygen addition and HPT processing. The increase in hardness was attributed to the microstructural refinement, to the creation of a high density of defects, and to the stress-induced ω-phase formation, which were all obtained due to the severe plastic deformation. Besides that, oxygen solid solution hardening provides a great increase in hardness. Vickers microhardness of approximately 400 HV was obtained for samples with higher oxygen content and deformed by HPT. The elastic modulus did not change significantly for the different oxygen levels, with values of 53–66 GPa. The typical Gum Metal properties were attained in the present paper, and they are directly related to its deformation mechanisms such as slip, stress-induced αʺ-martensite as well as reverse martensitic transformation (αʺ → β). The unique Gum Metal properties combined with the obtained increase in hardness make these two alloys very well suited for biomedical applications such as implants.

Differences in the effect of surface texturing on the wear loss of β-type Ti–Nb–Ta–Zr and (α+β)-type Ti–6Al–4V ELI alloys in contact with zirconia in physiological saline solution

The effectiveness of dimple surface texturing via picosecond pulsed laser processing for reducing wear loss was investigated using two types of titanium alloys, β-type Ti–29Nb–13Ta-4.6Zr (TNTZ) and α+β-type Ti–6Al–4V ELI (Ti64). The two alloys showed different modes of wear against zirconia. As the sliding distance increased, the wear loss was observed to increase for Ti64, but not necessarily for TNTZ. The wear debris of Ti64 acted as abrasive particles, but that of TNTZ easily adhered to the surface, and the adhered wear debris turned into a hard wear-protective layer. Therefore, the dependence of wear loss on the sliding distance for these two titanium alloys could be attributed to the difference in the roles of wear debris between each titanium alloy and zirconia. Further, depending on this difference in wear mode, the effect of dimple surface texturing on the wear was found to be different in Ti64 and TNTZ. As the dimples can trap the wear debris, they are effective for reducing wear in Ti64 but are detrimental in TNTZ.

Phase transformations in Ti–Nb–Zr–Ta–O beta titanium alloys with high oxygen and reduced Nb and Ta content

Phase transformations in Ti–Nb–Zr–Ta–O beta titanium alloys with high oxygen and reduced Nb and Ta content

Additive Manufacturing and Mechanical Properties of Functionally Graded Medical Ti–35Nb–7Zr–5Ta Porous Scaffolds

Functionally graded porous structure materials produced by additive manufacturing are promising for bone tissue engineering. Uniform and three kinds of gradient porous models (Radial, Axial, and Unidirectional) based on BCC unit were designed and built with selective laser melting. The research results show that: SLMed Uniform porous Ti–35Nb–7Zr–5Ta sample consists of a single β-Ti phase, and microstructure is composed of columnar crystal and cellular structure. The compression test shows that the radial gradient porous structure has higher yield strength (111 MPa), low elastic modulus (4.5 GPa), excellent plasticity, and energy absorption, which is more suitable for the construction of load-bearing orthopedic scaffold.