Beta Ti Alloys Research Articles

Bioactive surface modification of Ti–Nb alloy by alkaline treatment in potassium hydroxide solution

Abstract The aim of this work is to compare the responsive behaviour of titanium, niobium and titanium–niobium alloy during alkaline treatment in forming alkaline titanate layer and their resultant bioactive properties. Titanium and niobium powder mixture with composition in the beta region was pressed at 550 MPa and sintered at 1,200 °C for 2 h. The alloy was soaked in potassium hydroxide aqueous solution at 60 °C for 24 h with different concentrations of 0.5 M and 5 M. The effect of post sintering-heat treatment was investigated by annealing the treated alloy at 600 °C for 2 h. X-ray diffraction analysis and Fourier transform infrared spectroscopy analysis were used to evaluate the chemical composition and the functional group of material on the treated alloy surface respectively. Immersion in Hanks solution for 1 day resulted in traces of calcium and phosphate on alloy surfaces treated in different concentrations of alkali as well as post-heat treatment. The cell viability evaluation using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay on the new beta-Ti alloy with potassium-based titanate layer demonstrated potassium hydroxide treatment with a 5 M concentration after post-heat treatment significantly improved cell proliferation, which is a prerequisite for bone mineral apatite deposition.

Design and characterization of novel Ti-8Mo-xFe-yCu alloys as implant materials: Evaluation of biocompatibility, mechanical properties, and antibacterial potential

Titanium and its alloys are highly desirable materials for biomedical metallic implants due to their superior specific strength, excellent corrosion resistance, and exceptional biocompatibility. Among these alloys, Ti6Al4V is widely used in practical biomedical applications because it offers an excellent combination of strength, fracture toughness, and corrosion resistance. However, recent research has revealed limitations in its biocompatibility attributed to the presence of toxic elements such as Al and V. In addition, it has been reported that Ti6Al4V is costly due to the addition of Vanadium and has the potential for post-implant inflammation. As a result, researchers have been investigating new biomedical beta-Ti alloys using biocompatible, affordable, and easily accessible beta-stabilizers like Mo, Fe, and Cu, to achieve similar performance as Ti6Al4V alloys. The present study aims to develop a novel biomedical alloy through the arc melting method, to obtain an implant material possessing low elastic moduli, biocompatibility, and antibacterial properties to mitigate the risk of post-implant inflammation. Microstructural analysis was conducted using microscopy and x-ray diffraction, while the mechanical properties were evaluated through micro vickers hardness testing machine and elastic moduli measurement utilizing the impulse excitation technique. Cytotoxicity assessment was performed using the (Cell Counting Kit-8) CCK-8 method, followed by an examination of the alloy's antibacterial properties using the point counting method. β-Ti single phase was obtained in this study with the addition of ≥1% Fe and ≥1% Cu. The Ti-8Mo-2Fe-2Cu alloy was found to have the lowest elastic moduli of 95 GPa. Electrochemical measurements show that the Ti-8Mo- xFe- yCu alloys have a lower corrosion current density of around 0.319–2.317 µA/cm2 compared to Ti6Al4V of 16.543 µA/cm2. The Ti-8Mo-1Fe-3Cu, Ti-8Mo-3Fe-1Cu, and Ti-8Mo-3Fe-3Cu alloys have comparable biocompatibility with Ti6Al4V with the viability of mesenchymal stem cells (MSCs) above 75% and have a positive antibacterial response. Ti-8Mo-3Fe-3Cu alloy demonstrates the most favorable blend of microstructure, mechanical attributes, corrosion resistance, cell viability, and antibacterial properties as an alternate biomaterial for implant applications.

Effect of Partial Substitution of Zr for Ti Solvent on Young's Modulus, Strength, and Biocompatibility in Beta Ti Alloy.

In orthopedics and dentistry, there is an urgent need to obtain low-stiffness implants that suppress the stress shielding caused by the use of metallic implants. In this study, we aimed to fabricate alloys that can reduce the stiffness by increasing the strength while maintaining a low Young's modulus based on the metastable β-Ti alloy. We designed alloys in which Ti was partially replaced by Zr based on the ISO-approved metastable β-Ti alloy Ti-15Mo-5Zr-3Al. All alloys prepared by arc melting and subsequent solution treatment showed a single β-phase solid solution, with no formation of the ω-phase. The alloys exhibited a low Young's modulus equivalent to that of Ti-15Mo-5Zr-3Al and a high strength superior to that of Ti-15Mo-5Zr-3Al and Ti-6Al-4V. This strengthening was presumed to be due to solid-solution strengthening. The biocompatibility of the alloys was as good as or better than that of Ti-6Al-4V. These alloys have potential as metallic materials suitable for biomedical applications.

X-ray diffraction for phase identification in Ti-based alloys: benefits and limitations

X-ray diffraction (XRD) is routinely used to characterise Ti alloys, as it provides insight on structure-related aspects. However, there are no dedicated reports on its accuracy are available. To fill this gap, this work aims at examining the benefits and limitations of XRD analysis for phase identification in Ti-based alloys. It is worth mentioning that this study analyses both standard and experimental Ti alloys but the scope is primarily on alloys slow cooled from high temperature, thus characterised by equilibrium microstructures. To be comprehensive, this study considers the all spectrum of Ti alloys, ranging from alpha to beta Ti alloys. It is found that successful identification and quantification of the phases is achieved in the majority of the different type of Ti-based alloys. However, in some instances like for near-alpha alloys, the output of XRD analysis needs to be complemented with other characterisation techniques such as microscopy to be able to fully characterise the material. The correlation between the results of XRD analysis and the molybdenum equivalent parameter (MoE), which is widely used to design Ti alloys, was also investigated using structural-analytical models. The parallel model is found to be the best to estimate the amount of β-Ti phase as a function of the MoE parameter.

Effect of Oxygen on Static Recrystallization Behaviors of Biomedical Ti-Nb-Zr Alloys

Titanium alloys that are used in biomedical applications must possess biocompatibility and a low elastic modulus so that they protect host bone tissue without causing stress shielding. As the elastic modulus of beta Ti alloys is close to that of bone (10–30 GPa), these alloys are considered potential orthopedic implant materials. The elastic modulus of the single β-phase Ti-39Nb-6Zr (TNZ40) alloy is approximately 40 GPa, whereas the strength is lower than that of other types of Ti alloys. Interstitial oxygen in a Ti matrix is well known to improve the matrix strength by solid-solution hardening. The desired mechanical properties can be optimized using a thermo-mechanical procedure to maintain a low elastic modulus. In order to enhance the strength, TNZ40 alloys were fabricated with different amounts of oxygen. The TNZ-0.16O and TNZ-0.26O alloys were cold swaged into 11 mm diameter bars, subjected to solution treatment at 900 °C and 950 °C for 2 h, and furnace-cooled to room temperature. As a result, recrystallized grains were clearly observed in the β matrix. The TNZ-0.26O alloy that was cold-worked by swaging followed by solution treatment at 900 °C exhibited the best mechanical properties (Vickers hardness: 247 HV, ultimate tensile strength: 777 MPa, elongation at rupture: 18.6%, and compressive strength: 1187 MPa). This study reports the effects of oxygen content on the recrystallization behavior and mechanical properties of these alloys.

Laser-based resonant ultrasound spectroscopy for monitoring secondary phases in metastable Ti-alloys: From growth kinetics to high-throughput characterization

Metastable beta-Ti alloys undergo complex microstructural changes when annealed for extended times (hours, days, weeks) at temperatures below beta-transus. Contact-less RUS turns out to be a perfect tool for monitoring these processes, as well as for analyzing the properties of the alloys after the heat treatment. In the talk, we will illustrate this ability with three examples of recent advancements in this field. In particular, we will show that RUS is capable of analyzing (i) growth kinetics [1], from fast non-equilibrium phenomena to extremely slow processes; (ii) cubic symmetry conservation in single crystals with particles of various secondary phases [2]; and (iii) phase composition-elasticity relationships in series of oligocrystalline samples [3]. [1] Nejezchlebová et al. Elastic constants of β- Ti15Mo (2019) J Alloys Compounds, 792, pp. 960–967. [2] Olejňák et al. An ultrasound-based evaluation of cubic symmetry preservation and homogeneity in elastic behavior of β+ω and β+α Ti-alloys (2023) Materials and Design, 236, art. no. 112474. [3] Preisler et al., High-throughput characterization of elastic moduli of Ti-Nb-Zr-O biomedical alloys fabricated by field-assisted sintering technique (2023) J Alloys Compounds, 932, art. no. 167656.

Revealing the martensitic variant selection in metastable beta titanium alloy Ti–10V–2Fe–3Al under heterogeneous deformation

As an important deformation mode for the mechanical responses of titanium (Ti) alloys, the martensitic transformation has earned enormous interest, for example, the variant selection, under macro uniaxial stress by tension or compression. However, the variant selection under small-scale deformation with a complex loading condition was rarely reported. In the present study, the small-scale deformation of metastable beta Ti alloy was investigated using nanoindentation combined with the transmission electron microscope (TEM) observation. Different martensitic variants were detected under the complex strain/stress field given by the indenter in the single titanium crystal, which was well interpreted by the Schmid factor (SF) and interaction work (IW) criterion, with the assistance of finite element (FE) simulation. The same prediction given by SF and IW comes from the truth that SF for simple shear is a special case of the IW criterion.

Fine-tuning effect of Direct Laser Interference Patterning on the surface states and the corrosion behavior of a biomedical additively manufactured beta Ti alloy

Direct laser interference patterning (DLIP) is applied on additively manufactured near-beta Ti-13Nb-13Zr using nanosecond (ns) and picosecond (ps) pulses to tune its surface properties. Multiscale surface chemical and microstructural analyses (AES, XPS, XRD, SEM, TEM, GD-OES, contact angle) of those DLIP states are performed for understanding the corrosion behavior in a physiological PBS solution. Increased beta-phase fractions and uniformly thick passive layers of ns-DLIP surfaces led to enhanced corrosion stability compared to ps-DLIP with defective surface oxide. Both DLIP states control the surface wettability, thereby limiting corrosion and metal ion release rates, which is beneficial for implant applications.

Fine-Tuning Effect of Direct Laser Interference Patterning on the Surface States and the Corrosion Behavior of a Biomedical Additively Manufactured Beta Ti Alloy

Fine-Tuning Effect of Direct Laser Interference Patterning on the Surface States and the Corrosion Behavior of a Biomedical Additively Manufactured Beta Ti Alloy

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

Fatigue and corrosion resistance of low modulus Ti-35Nb-7Zr-5Ta-0.35O beta Ti alloy for orthopedic implant applications

This study has examined the influence of heat treatment on the fatigue response and electrochemical behavior of low modulus beta Ti alloy Ti-35Nb-7Zr-5Ta-0.35O. The heat treatment step comprised of a sub-transus solution treatment (750 °C-8h) followed by aging (300–500 °C). Fatigue studies have shown that low temperature aging at 300 °C-8h and 350 °C-16h exhibited a comparatively improved fatigue resistance. Highest cyclic fatigue strength was obtained after aging at 350 °C-16h, a fatigue strength of 460 MPa for a cyclic life of 1 × 106 cycles, this being attributed to the presence of fine nanoscale omega precipitates. Inferior fatigue performance was observed after high temperature aging (450 °C-32h and 500 °C-8h). Corrosion studies indicated improved electrochemical behavior after aging at 350 °C-16h, reduced corrosion resistance being observed after high temperature aging (500 °C-8h).

Achieving high strength and low elastic modulus in interstitial biomedical Ti–Nb–Zr–O alloys through compositional optimization

High strength and low elastic modulus are critical properties of biomedical titanium alloys for manufacturing of load-bearing orthopaedic implants. Single phase beta Ti alloys can achieve low elastic modulus, but their strength is usually not high enough. Conversely, commonly used strengthening by alpha phase precipitation causes a sharp increase of elastic modulus. This paper presents an approach for achieving both high strength and low elastic modulus by tailoring the alloy composition. High strength is achieved by controlled alloying with oxygen, which causes interstitial strengthening. Solid solution strengthening by Ta, which is often used in biomedical Ti alloys then becomes redundant. Low modulus is achieved due to premartensitic softening by tailoring the content of beta stabilizing elements – the stability of beta matrix is reduced due to the proximity to the martensitic transformation. Using this approach we obtained a compositionally optimized Ti–29Nb–7Zr-0.7O alloy, with yield stress exceeding 1000 MPa and elastic modulus of 65 GPa. High strength, low elastic modulus and good ductility are achieved by simple alloying without any additional special treatment. Ti–29Nb–7Zr-0.7O alloy appears promising for manufacturing of load bearing implants.

The role of thermal cycling on twinning in metastable beta-Ti alloy

Twinning in a Ti−26Nb alloy during thermal cycling was investigated by transmission electron microscopy. The interrelationships between displacive transformation and twinning were proposed. Fine {112}β1¯1¯1β twins and preferentially formed ω particles were observed in the β matrix after 100 cycles. The {112}β1¯1¯1β twins nucleated in ω particles and grew by merging twin embryos. Upon further increasing the cycle number to 500, {332}β113¯β twins bounded with laminated α" martensite were observed instead. The interfacial twin boundary α" phase mediated the martensitic transformation of the adjacent region, leading to the formation of {332}β113¯β twins.

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

Titanium alloys, especially Ti6Al4V, are commonly applied in orthopaedic implants as a result of their relatively low density, good corrosion properties, satisfactory biocompatibility and bone ingrowth promoting properties. However, Ti implants are susceptible to mechanical failure. Although corrosion and wear related problems have been recognized as a major issue impeding their long-term application, there is still a lack of knowledge about the basic mechanisms. Previously, the tribocorrosion properties of 4 distinct titanium alloys (Ti13Nb13Zr, Ti12Mo6Zr2Fe, Ti29Nb13Ta4.6Zr aged at 300 °C and at 400 °C) was analysed in the published Part I of this study in regard to wear rates, electrochemical behaviour, and the tribocorrosion synergism estimations. This work, Part II, contributes to the previous study and investigates the tested surfaces of these 4 Titanium alloys from the same tribosystem aiming to characterize the wear track surfaces and identify the main wear mechanism, to characterize the tribofilm and to investigate the subsurface alterations occurring under varying contact pressures and electrochemical potentials. The results indicated a dominant abrasion wear mechanism regardless of microstructure, electrochemical potential and normal load (contact pressure). Additionally, grain refinement observed on the subsurface varied with alloy and electrochemical potential, with the variation being mostly independent of alloy microstructure. Finally, a graphitic tribofilm was detected in most conditions, which while inconsequential in regard to wear, may explain the previously observed reduction of friction.Graphic

Effect of Supra-Transus Deformation Conditions on Recrystallization of Beta Ti Alloy

There is increasing usage of high strength Beta Ti alloy in aerospace components. However, one of the major challenges is to obtain homogeneous refined microstructures via the thermo-mechanical processing. To overcome this issue, an understanding of the hot deformation conditions effect on the microstructure, prior to and after annealing, is needed. In this work, the effect of strain levels, which is more precise than percentage of reduction, and strain rate under supra-transus deformation temperature on beta annealing are studied using a double cone sample. The Electron Backscattered Diffraction (EBSD) is used to determine the deformed microstructure and texture evolution, as well as the static recrystallized grains evolution using the ex situ annealing approach. This work provides evidence that the mechanisms of dynamic recovery and recrystallization, along with texture evolution, are affected by the deformation conditions, which in turn affected the subsequent static recrystallization during annealing. It will also be shown that high levels of strain do not necessarily lead to an increase in the rate of recrystallization. Finally, the results obtained provided several examples of guidance in designing the TMP processes for obtaining not only a refine microstructure, but a more homogeneous beta microstructure during the beta processing of Beta Ti alloy.

Novel α + β Zr Alloys with Enhanced Strength.

Low-alloyed zirconium alloys are widely used in nuclear applications due to their low neutron absorption cross-section. These alloys, however, suffer from limited strength. Well-established guidelines for the development of Ti alloys were applied to design new two-phase ternary Zr alloys with improved mechanical properties. Zr-4Sn-4Nb and Zr-8Sn-4Nb alloys have been manufactured by vacuum arc melting, thermo-mechanically processed by annealing, forging, and aging to various microstructural conditions and thoroughly characterized. Detailed Scanning electron microscopy (SEM) analysis showed that the microstructural response of the alloys is rather similar to alpha + beta Ti alloys. Duplex microstructure containing primary alpha phase particles surrounded by lamellar alpha + beta microstructure can be achieved by thermal processing. Mechanical properties strongly depend on the previous treatment. Ultimate tensile strength exceeding 700 MPa was achieved exceeding the strength of commercial Zr alloys for nuclear applications by more than 50%. Such an improvement in strength more than compensates for the increased neutron absorption cross-section. This study aims to exploit the potential of alpha + beta Zr alloys for nuclear applications.

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

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

The Role of Thermal Cycling on Twinning in Metastable Beta-Ti Alloy

The Role of Thermal Cycling on Twinning in Metastable Beta-Ti Alloy

Evaluation of mechanical properties, in vitro corrosion resistance and biocompatibility of Gum Metal in the context of implant applications

In recent decades, several novel Ti alloys have been developed in order to produce improved alternatives to the conventional alloys used in the biomedical industry such as commercially pure titanium or dual phase (alpha and beta) Ti alloys. Gum Metal with the non-toxic composition Ti–36Nb–2Ta–3Zr–0.3O (wt. %) is a relatively new alloy which belongs to the group of metastable beta Ti alloys. In this work, Gum Metal has been assessed in terms of its mechanical properties, corrosion resistance and cell culture response. The performance of Gum Metal was contrasted with that of Ti–6Al–4V ELI (extra-low interstitial) which is commonly used as a material for implants. The advantageous mechanical characteristics of Gum Metal, e.g. a relatively low Young's modulus (below 70 GPa), high strength (over 1000 MPa) and a large range of reversible deformation, that are important in the context of potential implant applications, were confirmed. Moreover, the results of short- and long-term electrochemical characterization of Gum Metal showed high corrosion resistance in Ringer's solution with varied pH. The corrosion resistance of Gum Metal was best in a weak acid environment. Potentiodynamic polarization studies revealed that Gum Metal is significantly less susceptible to pitting corrosion compared to Ti–6Al–4V ELI. The oxide layer on the Gum Metal surface was stable up to 8.5 V. Prior to cell culture, the surface conditions of the samples, such as nanohardness, roughness and chemical composition, were analyzed. Evaluation of the in vitro biocompatibility of the alloys was performed by cell attachment and spreading analysis after incubation for 48 h. Increased in vitro MC3T3-E1 osteoblast viability and proliferation on the Gum Metal samples was observed. Gum Metal presented excellent properties making it a suitable candidate for biomedical applications.

An exploratory study of TiO2-based multicomponent nanotubes on TiFeNbSn ultrafine eutectic alloy

Beta-Ti alloys with suitable bulk and surface properties are frequently studied to be used for biomedical applications. In this work, Ti66Fe20Nb8Sn6 (at.%) ultrafine eutectic alloy with dendritic morphology consisting of β-Ti matrix and TiFe and Ti3Sn intermetallic phases was submitted to electrochemical anodization aiming to explore the capability to support nanotubular structures. The anodizing parameters were varied, and, besides that, structural, microstructural, and surface properties were evaluated in different conditions. Results showed both nanotubular structures ordered on dendrites and non-homogeneous nanostructure grown on interdendritic regions. This fact was associated with compositional variations on the dendritic morphology that alter the diffusive process during nanotubes' growth. The Ti66Fe20Nb8Sn6 alloy composition is reflected in nanostructured film composition resulting in multicomponent oxides nanotubes. Annealed nanotubes showed amorphous and anatase-phase at 400 °C, and for annealing temperatures above (450–500 °C) it was evidenced the formation of TiO2 anatase and rutile phases. These phases' combination and morphology changes affect the surface properties such as roughness and wettability. However, it is noteworthy that all the conditions studied showed a hydrophilic behavior, becoming more hydrophilic when heat-treated at 400 °C (lower contact angle) combined with amorphous + anatase phases. The typical characteristics of Ti66Fe20Nb8Sn6 ultrafine eutectic alloy, including low elastic modulus (77 GPa) and dendritic morphology, together with surface properties (roughness and wettability), obtained by anodization followed by annealing, it is a good indicator and suggests a suitable nano-topography for potential biomedical applications.