Influence of Mo equivalent in the corrosion resistance of Ti-10Mo-xNb alloys

Influence of Mo equivalent in the corrosion resistance of Ti-10Mo-xNb alloys | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Influence of Mo equivalent in the corrosion resistance of Ti-10Mo-xNb alloys Ana Isabel Carvalho Santana, Sinara Borborema, Caio Marcello Felbinger Azevedo Cossu, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8195494/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract β-Ti alloys are gaining space in biomedical applications due their favorable combination of mechanical properties including their low elastic modulus and corrosion resistance. In this context, β titanium Ti-10Mo-xNb (x = 0, 6, 9, 20 and 30wt%) alloys were designed and produced. The relationship among the alloy composition, microstructure, and corrosion properties was investigated. The results were compared with those of the commercial Ti-6Al-4V and Ti(cp) alloys. Results showed that with increasing Mo equivalent, the contents of the α’’ and ω phases decreased, while the content of the β phase increased accordingly. The produced Ti-10Mo-xNb alloys exhibited hardness values higher than commercially pure Ti (cp). Among them the Ti-10Mo, Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys showed hardness values comparable to Ti-6Al-4V alloy. Furthermore, each alloy exhibited a lower elastic modulus than Ti-6Al-4V, with Ti-10Mo-20Nb (74 GPa) and Ti-10Mo-30Nb (94 GPa) showing significantly reduced values. All the Ti-10Mo-xNb alloys exhibited high corrosion resistance, attributed to the formation of a passive film after exposure to the physiological saline solution. The corrosion properties were evaluated using potentiodynamic polarization curves and chronoamperometry. Alloys with lower Nb contents (0 and 6%) exhibited relatively higher corrosion resistance, whereas those with higher Nb content showed reduced effectiveness of the protective film. This behavior can be related to the presence of fine α″-phase precipitates distributed within the matrix of the Ti-10Mo and Ti-10Mo-6Nb alloys. The Ti-10Mo-20Nb alloy, however, exhibits the most favorable overall balance, combining the lowest elastic modulus with high corrosion resistance. Ti-Mo-Nb alloys Corrosion mechanical properties biomaterial Microstructure Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Over the years, the demand for prosthetic devices has grown, driven by aging of the population and other factors such as the prevalence of traumatic injuries. In this context, biomaterials used for implants have gained significant attention [ 1 – 3 ]. Titanium and titanium alloys have been widely used as a biomaterial since 1960, owing their outstand combination of properties such as low Young’s modulus, high tensile strength, fatigue resistance, good ductility, excellent corrosion resistance to body fluids and superior biocompatibility compared to other metallic materials commonly applied as implants, such as Cr-Co alloys and stainless steels.[ 4 ]. The most popular Ti-alloy used is Ti-6Al-4V, that has very successful acceptance in the medical area.[ 4 – 9 ]. However, studies have shown that there is a relationship between vanadium with allergic reactions and some other problems to human health, additionally aluminum has been associated with neurological problems [ 10 – 12 ]. These findings show the importance of developing of new Ti alloys containing non-toxic elements with good properties for biomedical application as an alternative to conventional alloys. β-Ti alloys are the most promising ones when compared to the types α and α + β alloys. New β-Ti alloys with β-stabilizer elements such as Nb, Ta, Zr and Mo has been developed with lower Young’s modulus, better strength and good corrosion resistance [ 13 – 19 ]. β Ti alloys are classified as either stable and metastable. The stability of the β phaseis influenced by the concentration of β-stabilizing elements. This stability can be quantified using the “molybdenum equivalent” [ 19 ]. Metastable β titanium alloys undergo various phase transformations phases such as α’, α’’ and ω can be formed during thermomechanical processing. These transformations significantly affect mechanical properties and corrosion resistance of titanium alloys [ 20 – 21 ]. Furthermore, the presence of β-stabilizing elements such as Nb, Ta and Mo plays a crucial role in promoting the formation of a protective oxide layer, necessary for the good corrosion resistance of these materials [ 3 , 17 , 22 – 23 ]. Study conducted by Chelariu et al. [ 17 ] on Ti-Nb-Mo alloys showed that the capacitive behavior of passive films becomes more evident when the content of Nb increases and content of Mo decreases. The influence of niobium addition on the mechanical properties and corrosion resistance of titanium alloys has been extensively investigated in earlier studies. As previously mentioned, Nb is a β-phase stabilizing element, but there is still disagreement regarding its influence on corrosion resistance. Calderon-Moreno et al. [ 24 ] evaluated the Ti-15Zr-10Nb alloy in comparison with commercial pure Ti. A biphasic microstructure (α + β) of the Widmanstätten type was observed. Tests in Ringer's lactate medium at different pHs showed that the alloy containing Nb and Zr exhibited superior corrosion resistance under all evaluated conditions. Titanium alloys with different Nb and Mo contents were studied by Chelariu et al. [ 17 ] in 0.9% NaCl. It was observed that increasing the Nb content while decreasing the Mo concentration resulted in a reduction in both corrosion and passivation currents. In recent research, Cao et al . [ 25 ] evaluated the effect of the corrosive environment and heat treatment on the Ti-0.3Mo-0.8Ni alloy, obtained by additive manufacturing. The authors observed the formation of passive films after exposure to the corrosive environment (3,5 wt % NaCl). The authors observed that the Ti-0.3Mo-0.8Ni alloy showed greater corrosion resistance compared to commercially pure titanium (CP – Ti). This increase was attributed to the addition of molybdenum, which improves the stability of protective oxide, promoting the formation of more compact films with enhanced resistance to corrosion. Cvijovic-Alagic [ 26 ] evaluated the corrosion resistance of the Ti-13Nb-13Zr alloy with α' martensitic microstructure (acicular martensite) in a β matrix, in Ringer's solution at 37 o C. The electrochemical behavior of this alloy was compared with Ti-6Al-4V with an α' martensitic microstructure (needlelike martensitic morphology) and Ti-6Al-4V (α + β biphasic). The results showed that both alloys with martensitic microstructure (Ti-13Nb-13Zr and Ti-6Al-4V) exhibited higher corrosion resistance compared to the biphasic alloy (Ti-6Al-4V - α + β). This superior result was attributed to the more homogeneous distribution of alloying elements in the α′ phase, favoring the formation of a more compact and homogeneous passive film, enhancing stability against corrosive attack. Song et al . [ 27 ] evaluated a new titanium alloy (Ti-5 Nb-3Mo-3 V-3Al-2Zr-1Fe) with a biphasic (α + β) microstructure. The authors observed that, depending on the heat treatment applied, different secondary phases, such as α″, ω, and O' could be present in the alloy’s microstructure. Electrochemical tests conducted in 3.5% NaCl solution showed that the alloy containing the intermediate ω and O' phases exhibited the highest corrosion resistance. This behavior was attributed to the formation of fine and homogeneously distributed α phase precipitates, resulting from the assisting mechanism of the ω and O' phases. The α phase formed from these intermediates increased the number of α/β interfaces, facilitating oxygen diffusion and promoting the development of more compact and homogeneous passive films. These films, in turn, provided a better barrier effect, thereby enhancing the alloy's corrosion resistance. Therefore, in this work, β titanium Ti-10Mo-xNb (x = 0, 6, 9, 20 and 30 wt%) alloys were produced and the relationship among alloy composition, microstructure, mechanical properties and corrosion behavior were analyzed as a function of Nb content. 2. Material and Methods The Ti-10Mo-xNb (0, 6, 9, 20 and 30 wt%) alloys were produced from commercially pure Ti (grade 2 according to ASTM F6706), Mo (> 99.9% pure, supplied by Plansee Group, Austria) and Nb (> 99.9% pure, supplied by EEL/USP, Brazil) metals. An arc melting process with a tungsten electrode on a water-cooled copper hearth was employed to melt the alloys. These were prepared under high purity argon atmosphere (> 99.9999% pure), and the ingots were melted seven times to guarantee chemical homogeneity. The obtained ingots were solution-treated at 950 ºC under argon atmosphere for 1 hour and then quenched in water at room temperature. The structural characterization of the alloys (polished samples) was carried out by X-ray diffraction (XRD) operated at 40 kV and 30 mA. A Ni-filtered CuK α radiation (λ = 0.15418 nm) was used. The microstructures were investigated by scanning electron microscopy (LEO-ZEISS 1450 VP SEM). The samples were polished by standard metallographic techniques and etched with Kroll’s reagent (3 mL of HF, 6 mL of HNO 3 and 100 mL H 2 O). The microstructures of alloys were also analyzed by transmission electron microscopy (TEM) operating at 200 kV. Thin foils were prepared by twin-jet electropolishing in a solution containing 60 mL HClO 4 , 590 mL methanol, and 350 mL ether-monobutylethylene at 35 V and − 20 ºC. The hardness and elastic modulus of ASTM F67 commercially pure titanium grade 2 and ASTM F136 Ti-6Al-4V wrought annealed alloy were also replicated for comparison under the same conditions described above. The Vickers microhardness (HV) was measured using a set of 10 indentations with an applied load of 100 gf and a indentation time of 30 seconds. The elastic modulus (E) of the alloys was determined by ultrasonic-pulse method. Five measurements were performed for each sample. The electrochemical behavior of Ti-10Mo, Ti-10Mo-6Nb, Ti-10Mo-9Nb, Ti-10Mo-20Nb, Ti-10Mo-30Nb and Ti-6Al-4V alloys in a naturally aerated physiological solution of 0.9% NaCl at room temperature. The tests were investigated using a PGSTAT 302N AUTOLAB potentiostat. The samples were prepared by embedding the alloys in epoxy resin left to cure. After curing, the surfaces exposed to the electrolyte were prepared by sequentially sanding with silicon carbide paper, followed by washing with water and alcohol, alcohol and then drying with an air jet. The electrochemical tests consisted of measuring the open circuit potential, potentiodynamic polarization curves and chronoamperometry. All measurements were conducted using a three-electrode corrosion cell. In this setup, the alloys served as the working electrode, a platinum wire was employed as the counter electrode, and a saturated calomel electrode (SCE) was utilized as the reference electrode. The open circuit potential was monitored over a period of 3600 s. After this time, polarization curves were obtained in a potential range between 0.25 V and 1.60 V versus the saturated calomel electrode. The curves were carried out at a scan rate of 1mV/s. The chronoamperometry tests were carried out at a potential of E = 1.6 V, over a period of 1 hour, under the same experimental conditions as mentioned above. 3. Results and Discussion 3.1 Microstructural characterization Figure 1 shows the X- ray diffractograms (highlighting the peaks near the background) of theTi-10Mo, Ti-10Mo-6Nb, Ti-10Mo-9Nb, Ti-10Mo-20Nb, and Ti-10Mo-30Nb alloys. Reflections from the (α’’ + ω) phases were identified in the β matrix of the Ti-10Mo and Ti-10Mo-6Nb alloys. The XRD diffraction of Ti-10Mo-9Nb alloy showed only reflections from the α’’phase in the β matrix. The results showed than the microstructure change from (β + α″ + ω) → (β + α″) phases to single β phase in Ti-10Mo-20Nb and Ti-10Mo-30Nb alloys with Nb addition, showing that the Nb addition resulted in the β-phase stability. This is in accordance with the literature showing that β-phase stability in titanium alloys can be assessed using the molybdenum equivalent [Mo eq ]. If the [Mo eq ] value is higher than 10% [ 28 ], β phase metastable is retained during quenching from temperatures (above the β transus). Below this value, α’ (hexagonal), α’’(orthorhombic) and ω phase (hcp structure) may precipitate in the β-Ti matrix. In addition, the cooling rate has a predominant role in the phases transformation in Ti alloys [ 29 – 30 ]. Figure 2 shows optical micrographs of (a) Ti-10Mo, (b) Ti-10Mo-6Nb, (c) Ti-10Mo-9Nb (d) Ti-10Mo-20Nb and (e) Ti-10Mo-30Nb alloys. The adopted solution treatment could not eliminate completely the as-cast dendrite structures. This effect was more evident in the alloy with lower Nb content and is attributed to the low treatment temperature (950°C) and short duration. A fine acicular α’’phase was observed in the β matrix of Ti-10Mo [Mo eq = 10.0], Ti-10Mo-6Nb [Mo eq = 11.7] and Ti-10Mo-9Nb [Mo eq = 12.5] alloys, mainly on the on the Ti-10Mo alloy (Fig. 2 a). It was verified than α’’ phase decreases for higher Nb contents. It was observed only single β phase in Ti-10Mo-20Nb and Ti-10Mo-30Nb alloys. 3.2 Mechanical characterization Table 1 provides the measured values of hardness and elastic modulus (E) of Ti-10Mo, Ti-10Mo-6Nb, Ti-10Mo-9Nb, Ti-10Mo-20Nb, Ti-10Mo-30Nb, Ti-6Al-4V alloys and Ti (cp). The Ti-10Mo-xNb alloys showed a small variation in the hardness with Nb addition up to 9%, however with the increase in the Nb content a significant decrease was observed. This increase in Nb is related to the suppression of the α'' phase, since it is observed by the optical microscopy and XRD results shown that the Ti-10Mo alloy is the one with the highest amount of martensitic phase, followed by the Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys. The α'' martensitic phase usually leads to a decrease in hardness in the alloys [ 31 ]. The standard deviation observed in the Ti-10Mo alloy is much higher than for the other alloys. This is related to the phases present in the alloy and their volume. All alloys presented hardness values higher than that of Ti cp, and the Ti-10Mo, Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys presented hardness values close to those of the Ti-6Al-4V alloy. The elastic modulus values of the alloys with Ti (cp) and the Ti-6Al-4V alloy are shown in Table 1 . The Ti-10Mo, Ti-10Mo-20Nb and Ti-10Mo-30Nb alloys showed lower elastic modulus compared to Ti (cp), Ti-6Al-4V and the other alloys. On the other hand, the Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys showed a modulus similar to Ti (cp) and the Ti-6Al-4V alloy. A notably low elastic modulus was obtained for Ti-10Mo-20Nb wish exhibited only β phase in its microstructure. Thid result is in agreement with previous studies of Li et al. [ 32 ] who reported that the elastic modulus in Ti alloys typically follows the order ω > α > α' >α" >β phases. The decreasing of elastic modulus of Ti-10Mo-20Nb alloy when compared with the largely used Ti-6Al-4V is around 40%. A close match between the elastic modulus of bone and the alloy is desirable, as it promotes uniform stress distribution and enhances the mechanical stability of the adjacent bone tissue. Table 1 Hardness (H) and elastic modulus (E) values of Ti-10Mo, Ti-10Mo-6Nb, Ti-10Mo-9Nb, Ti-10Mo-20Nb, Ti-10Mo-30Nb, Ti-6Al-4V alloys and Ti (cp). Alloys Hardness (H) (HV) Modulus (E) (GPa) Ti-10Mo 318.47 ± 24.43 107.05 ± 0.31 Ti-10Mo-6Nb 339.77 ± 5.69 122.44 ± 0.26 Ti-10Mo-9Nb 340.46 ± 6.21 120.12 ± 0.84 Ti-10Mo-20Nb 238.18 ± 10.75 74.30 ± 0.24 Ti-10Mo-30Nb 249.33 ± 4.98 94.74 ± 0.09 Ti-6Al-4V 337.31 ± 15.81 123.76 ± 4.41 Ti (cp) 174.89 ± 8.93 120.67 ± 5.85 The hardness-to-modulus ratio (H/E) is a key parameter in the selection of biomaterials for bone implant applications, particularly in the early stages of evaluation prior to more complex mechanical tests such as tensile and compression testing. This ratio directly affects stress distribution between the implant and the surrounding bone tissue. Higher H/E values are typically associated with improved wear resistance and a reduced risk of stress shielding, thereby helping to minimize bone resorption caused by significant stiffness mismatches between the implant material and the host bone [ 33 – 35 ]. Figure 3 presents a comparison between Ti (cp), Ti alloys commonly used in biomedical applications [ 36 – 39 ], and alloys from the Ti-10Mo-xNb system (x = 0, 6, 9, 20, and 30). Among all alloys, the highest H/E ratio was obtained for the Ti-10Mo-20Nb alloy, which exhibited only the β phase in its microstructure, followed by the Ti-10Mo alloy, characterized by a microstructure composed of α’’ and ω phases within the β matrix. The electrochemical behaviour of the Ti-10Mo-xNb (x = 0, 6, 9, 20 e 30%p Nb) in physiological saline solution is present in Figs. 4 to 6 . The corrosion potential (E corr ) of the alloys was measured by monitoring the open circuit potential after immersion in the salt solution for 1 hour. The variation in E corr with immersion time is shown in Fig. 4 . For all the alloys evaluated, the potential starts at more negative values and tends to evolve towards higher potentials with increasing time. The corrosion potential increases continuously until approximately 1000 s, after which time it remains stable during the test. This behaviour suggests the spontaneous formation of a protective film on the surface of the alloy. The formation of a protective oxide is natural for titanium alloys, as previous studies have shown [ 4 , 23 , 40 – 43 ]. There is a common understanding that the chemical composition of the alloy and the phases present have an influence on film formation, but this is still a matter of controversy. In the present work, two distinct behaviors were observed in relation to the corrosion potential. For the Ti-10Mo, Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys, the corrosion potential starts near E = -0.500 V (SCE) and gradually increases until it reaches a stable level at E = -0.398 V, -0.227 V and − 0.362 V (SCE) respectively. Ti-10Mo-20Nb and Ti-10Mo-30Nb corrosion potential begins in the most negative values, around E = -0.650V (SCE), gradually evolves to more noble potentials around E = -0.422 V for the 20%w Nb and E = -0.534 for the 30%w Nb alloy. This behaviour shows that regardless of composition, all the alloys evaluated show passive behaviour through the spontaneous formation of protective oxide. Figure 5 shows the potentiodynamic polarization curves carried out on the Ti-10Mo-xNb alloys. The curves were obtained after stabilization of the open circuit potential, after a period of 1 hour. The results show that regardless of the chemical composition of the alloy and the phases present, all the curves show a similar behavior, typical of passive alloys. Two typical regions are observed in the polarization curves. The first (region I - active zone) is characterized by an increase in current as the potential rises to approximately E = 0.050 V (SCE). From this potential onwards, the current stops varying and remains constant, initiating region II (passive zone), which is characterized by the formation of the passive film. The potential E = 0.500 V was chosen to measure the passivation current (i pass ) characteristic of region II. Table 2 shows the electrochemical parameters E corr and i pass obtained by monitoring the open circuit potential and polarization curves. The passive current density values (i pass ) obtained of the order between 6–10 µA.cm − 2 . These values are close to those observed in other studies for titanium alloys with similar composition [ 4 , 16 , 23 ]. The results showed that increasing the Nb content in the alloy promotes the stabilization of the β phase. The alloys with the highest Nb content (20 and 30%w) show higher current density values in the passive region, indicating the formation of a less resistant oxide film compared to the films formed in the presence of the α and ω phases. Although some authors attribute the presence of β-stabilizer elements as responsible for an increase in corrosion resistance in Ti alloys [ 9 , 44 ], in a recent study [ 27 ] was observed that the presence of fine α-phase precipitates in the β-matrix in the Ti-5Nb-3Mo-3V-3Al-2Zr-1Fe alloy was responsible for the increase in the mechanical properties and corrosion resistance of the alloy. This explanation could be applied to understanding the electrochemical behavior of Ti-10Mo-xNb alloys. In this case, the presence of fine and homogeneous of α ” precipitates resulting in an increase in the alloy's corrosion resistance. Table 2 – Corrosion potential and corrosion current density determined from polarization curves of Ti-10Mo-20Nb, Ti–12Mo–13Nb and Ti-6Al-4V alloys in physiological saline solution. Alloys Phases E corr (V (SCE) ) I pass (A/cm 2 ) Ti-10Mo α " + ω in β matrix -0.398 6.015 x 10 − 6 Ti-10Mo-6Nb α"+ω in β matrix -0.227 6.154 x 10 − 6 Ti-10Mo-9Nb α"+ω in β matrix -0.362 7.650 x 10 − 6 Ti-10Mo-20Nb β matrix -0.422 9.957 x 10 − 6 Ti-10Mo-30Nb β matrix -0.534 1.077 x 10 − 5 The chronoamperometry assays presented in Fig. 6 provide insight to understand the behavior of the passive film under different potential conditions. The results show the current transients as a function of time, obtained for the Ti-10Mo-xNb alloys at a fixed potential of E = 1.6V. This potential enables the evatuation of whether the film remains intact at higher potentials than those applied during potentiodynamic polarization tests, allowing assessment of the film’s integrity under more aggressive electrochemical conditions. The transient profiles one-hour period shows a drop in current in the initial moments (~ 500 s), after which the values remain stable for the rest of the experiment. This behavior clearly demonstrates the formation of the passive film on the surface of all the samples studied, regardless of the Nb content in the Ti-10Mo alloy. Similar behavior was observed by [ 4 ] when evaluating the effect of adding Ga to Ti-45Nb alloys. The authors related the drop in current response to the formation of a stable, compact and protective passive film during sample polarization. However, although all the alloys show the formation of a passive film that remained stable throughout the test period, it is worth noting that the formation of this film occurs more quickly for the Ti-10Mo and Ti-10Mo-6Nb alloys. Table 2 shows the current response obtained for the times of 250 s and 3600 s (end of the test). The results clearly show that the passive film forms more easily for samples with the lowest niobium content. This behavior indicates that, although the addition of niobium does not hinder the formation and stability of the passive film, there appears to be an optimum concentration (0–6% Nb) that promotes faster oxide growth upon exposure to the physiological solution. Table 3 – Current density determined from Chronoamperometry curves of Ti-10Mo-20Nb, Ti–12Mo–13Nb and Ti-6Al-4V alloys in physiological solution of 0.9% NaCl naturally aerated. Alloys Phases I 250s (A/cm 2 ) ) I 3600s (A/cm 2 ) Ti-10Mo α’’+ω in β matrix 9.45 x 10 − 6 1.97 x 10 − 6 Ti-10Mo-6Nb α’’+ω in β matrix 9.15 x 10 − 6 1.51 x 10 − 6 Ti-10Mo-9Nb α’’+ω in β matrix 2.40 x 10 − 5 7.09 x 10 − 6 Ti-10Mo-20Nb β matrix 2.75 x 10 − 5 8.13 x 10 − 6 Ti-10Mo-30Nb β matrix 3.18 x 10 − 5 6.65 x 10 − 5 In the present work, all the Ti-10Mo-xNb alloys evaluated showed high corrosion resistance, due to the spontaneous formation of the titanium oxide film, and this behavior is evident in the evolution of the corrosion potential. However, the polarization curves and chronoamperometry tests showed that for Nb content > 6% the corrosion resistance tends to decrease. Although numerous studies (e.g., [references]) have reported that the addition of Nb enhances the corrosion resistance of Ti alloys, recent investigations [ 27 ] have observed that the presence of ω-phase and α ” - martensitic precipitates can further promote the development of more protective passive films. Similarly, the results obtained in the present study show that the presence of fine α’’- phase precipitates exert a more effective influence over the beneficial effect of Nb incorporation on corrosion resistance, within the evaluated experimental conditions. 4. CONCLUSION The microstructural characterization results of the Ti-10Mo-xNb (x = 0, 6, 9, 20, and 30) alloys showed than the microstructure change from β + α″+ω → β + α″ phases to single β phase in Ti-10Mo-20Nb and Ti-10Mo-30Nb alloys with Nb addition, showing that the Nb addition resulted in the β-phase stability. All alloys presented hardness values higher than that of Ti (cp), and the Ti-10Mo, Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys presented hardness values close to those of the Ti-6Al-4V alloy. The alloys Ti-10Mo, Ti-10Mo-20Nb and Ti-10Mo-30Nb alloys showed lower elastic modulus compared to Ti (cp), Ti-6Al-4V alloys. On the other hand, the Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys showed a modulus similar to Ti (cp) and the Ti-6Al-4V alloy. The lower elastic modulus of designed alloys was obtained for Ti-10Mo-20Nb than presented only β phase in the microstructure. Among all the alloys, the highest H/E ratio was obtained for the Ti-10Mo-20Nb alloy, which exhibited only the β phase in its microstructure, followed by the Ti-10Mo alloy, characterized by a microstructure composed of α and ω phases within the β matrix. The corrosion resistance of the Ti-10Mo-xNb alloys was evaluated through electrochemical assays. All the alloys exhibited high corrosion resistance, mainly related to the formation of the titanium oxide film, which enables the alloy to be passivated and protected. It was observed that the addition of niobium to the Ti-Mo alloy promotes improvements in the quality of the passive film, as evidenced by the more noble corrosion potential and lower passivation current. However, at contents higher than 6% Nb, the corrosion resistance tends to decrease. The combination of electrochemical and mechanical results indicates that, among the alloys evaluated, Ti-10Mo is the one that presents the best combination of results. 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Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 03 Feb, 2026 Reviewers agreed at journal 02 Feb, 2026 Reviews received at journal 28 Jan, 2026 Reviewers agreed at journal 22 Jan, 2026 Reviews received at journal 17 Dec, 2025 Reviewers agreed at journal 11 Dec, 2025 Reviewers agreed at journal 09 Dec, 2025 Reviewers invited by journal 06 Dec, 2025 Editor assigned by journal 28 Nov, 2025 Submission checks completed at journal 25 Nov, 2025 First submitted to journal 24 Nov, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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1","display":"","copyAsset":false,"role":"figure","size":70433,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eXRD pattern of the Ti-10Mo-xNb alloys.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8195494/v1/b3c25066ed73852d7a5ab286.jpeg"},{"id":98096547,"identity":"443f7e30-b5fb-4352-b3e8-93049d40ad56","added_by":"auto","created_at":"2025-12-12 18:59:05","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":270589,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOptical micrographs of the Ti-10Mo-xNb alloys: (a) Ti-10Mo, (b) Ti-10Mo-6Nb, (c) Ti-10Mo-9Nb, (d) Ti-10Mo-20Nb and (e) Ti-10Mo-30Nb alloys.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8195494/v1/49baed6fec49244219400767.jpeg"},{"id":98096544,"identity":"d846e19e-9513-4d25-8758-73a6cae1b9f1","added_by":"auto","created_at":"2025-12-12 18:59:05","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":24838,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOptical micrographs of the Ti-10Mo-xNb alloys: (a) Ti-10Mo, (b) Ti-10Mo-6Nb, (c) Ti-10Mo-9Nb, (d) Ti-10Mo-20Nb and (e) Ti-10Mo-30Nb alloys.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8195494/v1/68d3d8c38844e3837c10a393.png"},{"id":98429953,"identity":"0f1089ac-8a98-4310-b171-5d406a526c80","added_by":"auto","created_at":"2025-12-17 16:44:28","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":92567,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOpen circuit potential measurements variation with time of Ti-10Mo-xNb alloys in physiological solution of 0.9% NaCl naturally aerated, at room temperature.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8195494/v1/573d333ed0413bd14ed8dc6d.jpeg"},{"id":98096552,"identity":"010da5c2-427e-4f55-8bed-c30a87ca77d0","added_by":"auto","created_at":"2025-12-12 18:59:05","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":105715,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePotentiodynamic polatization curve for Ti-10Mo-xNb alloys in physiological solution of 0.9% NaCl naturally aerated, at room temperature.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8195494/v1/c1f9cb582d5b5695cf0b6b7b.jpeg"},{"id":98428338,"identity":"c77476dd-9d9d-4c79-84bb-73470fd27e30","added_by":"auto","created_at":"2025-12-17 16:41:55","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":127906,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eChronoamperometry curves for Ti-10Mo-xNb alloys, at E = 1.6V in physiological solution of 0.9% NaCl naturally aerated, at room temperature.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8195494/v1/3cb301b777efba4e289e32c6.jpeg"},{"id":98444749,"identity":"516a4762-7339-4a65-90ba-599b8b6bc24a","added_by":"auto","created_at":"2025-12-17 17:17:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1608712,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8195494/v1/b7ce79b0-85f3-4a5d-bc8b-75039a27385a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Influence of Mo equivalent in the corrosion resistance of Ti-10Mo-xNb alloys","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eOver the years, the demand for prosthetic devices has grown, driven by aging of the population and other factors such as the prevalence of traumatic injuries. In this context, biomaterials used for implants have gained significant attention [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Titanium and titanium alloys have been widely used as a biomaterial since 1960, owing their outstand combination of properties such as low Young\u0026rsquo;s modulus, high tensile strength, fatigue resistance, good ductility, excellent corrosion resistance to body fluids and superior biocompatibility compared to other metallic materials commonly applied as implants, such as Cr-Co alloys and stainless steels.[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The most popular Ti-alloy used is Ti-6Al-4V, that has very successful acceptance in the medical area.[\u003cspan additionalcitationids=\"CR5 CR6 CR7 CR8\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eHowever, studies have shown that there is a relationship between vanadium with allergic reactions and some other problems to human health, additionally aluminum has been associated with neurological problems [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. These findings show the importance of developing of new Ti alloys containing non-toxic elements with good properties for biomedical application as an alternative to conventional alloys. β-Ti alloys are the most promising ones when compared to the types α and α\u0026thinsp;+\u0026thinsp;β alloys. New β-Ti alloys with β-stabilizer elements such as Nb, Ta, Zr and Mo has been developed with lower Young\u0026rsquo;s modulus, better strength and good corrosion resistance [\u003cspan additionalcitationids=\"CR14 CR15 CR16 CR17 CR18\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eβ Ti alloys are classified as either stable and metastable. The stability of the β phaseis influenced by the concentration of β-stabilizing elements. This stability can be quantified using the \u0026ldquo;molybdenum equivalent\u0026rdquo; [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Metastable β titanium alloys undergo various phase transformations phases such as α\u0026rsquo;, α\u0026rsquo;\u0026rsquo; and ω can be formed during thermomechanical processing. These transformations significantly affect mechanical properties and corrosion resistance of titanium alloys [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eFurthermore, the presence of β-stabilizing elements such as Nb, Ta and Mo plays a crucial role in promoting the formation of a protective oxide layer, necessary for the good corrosion resistance of these materials [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Study conducted by Chelariu \u003cem\u003eet al.\u003c/em\u003e [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] on Ti-Nb-Mo alloys showed that the capacitive behavior of passive films becomes more evident when the content of Nb increases and content of Mo decreases.\u003c/p\u003e\u003cp\u003eThe influence of niobium addition on the mechanical properties and corrosion resistance of titanium alloys has been extensively investigated in earlier studies. As previously mentioned, Nb is a β-phase stabilizing element, but there is still disagreement regarding its influence on corrosion resistance. Calderon-Moreno \u003cem\u003eet al.\u003c/em\u003e [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] evaluated the Ti-15Zr-10Nb alloy in comparison with commercial pure Ti. A biphasic microstructure (α\u0026thinsp;+\u0026thinsp;β) of the Widmanst\u0026auml;tten type was observed. Tests in Ringer's lactate medium at different pHs showed that the alloy containing Nb and Zr exhibited superior corrosion resistance under all evaluated conditions. Titanium alloys with different Nb and Mo contents were studied by Chelariu \u003cem\u003eet al.\u003c/em\u003e [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] in 0.9% NaCl. It was observed that increasing the Nb content while decreasing the Mo concentration resulted in a reduction in both corrosion and passivation currents.\u003c/p\u003e\u003cp\u003eIn recent research, Cao \u003cem\u003eet al\u003c/em\u003e. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] evaluated the effect of the corrosive environment and heat treatment on the Ti-0.3Mo-0.8Ni alloy, obtained by additive manufacturing. The authors observed the formation of passive films after exposure to the corrosive environment (3,5 wt % NaCl). The authors observed that the Ti-0.3Mo-0.8Ni alloy showed greater corrosion resistance compared to commercially pure titanium (CP \u0026ndash; Ti). This increase was attributed to the addition of molybdenum, which improves the stability of protective oxide, promoting the formation of more compact films with enhanced resistance to corrosion.\u003c/p\u003e\u003cp\u003eCvijovic-Alagic [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] evaluated the corrosion resistance of the Ti-13Nb-13Zr alloy with α' martensitic microstructure (acicular martensite) in a β matrix, in Ringer's solution at 37\u003csup\u003eo\u003c/sup\u003eC. The electrochemical behavior of this alloy was compared with Ti-6Al-4V with an α' martensitic microstructure (needlelike martensitic morphology) and Ti-6Al-4V (α\u0026thinsp;+\u0026thinsp;β biphasic). The results showed that both alloys with martensitic microstructure (Ti-13Nb-13Zr and Ti-6Al-4V) exhibited higher corrosion resistance compared to the biphasic alloy (Ti-6Al-4V - α\u0026thinsp;+\u0026thinsp;β). This superior result was attributed to the more homogeneous distribution of alloying elements in the α\u0026prime; phase, favoring the formation of a more compact and homogeneous passive film, enhancing stability against corrosive attack.\u003c/p\u003e\u003cp\u003eSong \u003cem\u003eet al\u003c/em\u003e. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] evaluated a new titanium alloy (Ti-5 Nb-3Mo-3 V-3Al-2Zr-1Fe) with a biphasic (α\u0026thinsp;+\u0026thinsp;β) microstructure. The authors observed that, depending on the heat treatment applied, different secondary phases, such as α\u0026Prime;, ω, and O' could be present in the alloy\u0026rsquo;s microstructure. Electrochemical tests conducted in 3.5% NaCl solution showed that the alloy containing the intermediate ω and O' phases exhibited the highest corrosion resistance. This behavior was attributed to the formation of fine and homogeneously distributed α phase precipitates, resulting from the assisting mechanism of the ω and O' phases. The α phase formed from these intermediates increased the number of α/β interfaces, facilitating oxygen diffusion and promoting the development of more compact and homogeneous passive films. These films, in turn, provided a better barrier effect, thereby enhancing the alloy's corrosion resistance.\u003c/p\u003e\u003cp\u003eTherefore, in this work, β titanium Ti-10Mo-xNb (x\u0026thinsp;=\u0026thinsp;0, 6, 9, 20 and 30 wt%) alloys were produced and the relationship among alloy composition, microstructure, mechanical properties and corrosion behavior were analyzed as a function of Nb content.\u003c/p\u003e"},{"header":"2. Material and Methods","content":"\u003cp\u003eThe Ti-10Mo-xNb (0, 6, 9, 20 and 30 wt%) alloys were produced from commercially pure Ti (grade 2 according to ASTM F6706), Mo (\u0026gt;\u0026thinsp;99.9% pure, supplied by Plansee Group, Austria) and Nb (\u0026gt;\u0026thinsp;99.9% pure, supplied by EEL/USP, Brazil) metals. An arc melting process with a tungsten electrode on a water-cooled copper hearth was employed to melt the alloys. These were prepared under high purity argon atmosphere (\u0026gt;\u0026thinsp;99.9999% pure), and the ingots were melted seven times to guarantee chemical homogeneity. The obtained ingots were solution-treated at 950 \u0026ordm;C under argon atmosphere for 1 hour and then quenched in water at room temperature.\u003c/p\u003e\u003cp\u003eThe structural characterization of the alloys (polished samples) was carried out by X-ray diffraction (XRD) operated at 40 kV and 30 mA. A Ni-filtered CuK\u003csub\u003eα\u003c/sub\u003e radiation (λ\u0026thinsp;=\u0026thinsp;0.15418 nm) was used.\u003c/p\u003e\u003cp\u003eThe microstructures were investigated by scanning electron microscopy (LEO-ZEISS 1450 VP SEM). The samples were polished by standard metallographic techniques and etched with Kroll\u0026rsquo;s reagent (3 mL of HF, 6 mL of HNO\u003csub\u003e3\u003c/sub\u003e and 100 mL H\u003csub\u003e2\u003c/sub\u003eO). The microstructures of alloys were also analyzed by transmission electron microscopy (TEM) operating at 200 kV. Thin foils were prepared by twin-jet electropolishing in a solution containing 60 mL HClO\u003csub\u003e4\u003c/sub\u003e, 590 mL methanol, and 350 mL ether-monobutylethylene at 35 V and \u0026minus;\u0026thinsp;20 \u0026ordm;C.\u003c/p\u003e\u003cp\u003eThe hardness and elastic modulus of ASTM F67 commercially pure titanium grade 2 and ASTM F136 Ti-6Al-4V wrought annealed alloy were also replicated for comparison under the same conditions described above. The Vickers microhardness (HV) was measured using a set of 10 indentations with an applied load of 100 gf and a indentation time of 30 seconds. The elastic modulus (E) of the alloys was determined by ultrasonic-pulse method. Five measurements were performed for each sample.\u003c/p\u003e\u003cp\u003eThe electrochemical behavior of Ti-10Mo, Ti-10Mo-6Nb, Ti-10Mo-9Nb, Ti-10Mo-20Nb, Ti-10Mo-30Nb and Ti-6Al-4V alloys in a naturally aerated physiological solution of 0.9% NaCl at room temperature. The tests were investigated using a PGSTAT 302N AUTOLAB potentiostat. The samples were prepared by embedding the alloys in epoxy resin left to cure. After curing, the surfaces exposed to the electrolyte were prepared by sequentially sanding with silicon carbide paper, followed by washing with water and alcohol, alcohol and then drying with an air jet. The electrochemical tests consisted of measuring the open circuit potential, potentiodynamic polarization curves and chronoamperometry.\u003c/p\u003e\u003cp\u003eAll measurements were conducted using a three-electrode corrosion cell. In this setup, the alloys served as the working electrode, a platinum wire was employed as the counter electrode, and a saturated calomel electrode (SCE) was utilized as the reference electrode. The open circuit potential was monitored over a period of 3600 s. After this time, polarization curves were obtained in a potential range between 0.25 V and 1.60 V versus the saturated calomel electrode. The curves were carried out at a scan rate of 1mV/s. The chronoamperometry tests were carried out at a potential of E\u0026thinsp;=\u0026thinsp;1.6 V, over a period of 1 hour, under the same experimental conditions as mentioned above.\u003c/p\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Microstructural characterization\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the X- ray diffractograms (highlighting the peaks near the background) of theTi-10Mo, Ti-10Mo-6Nb, Ti-10Mo-9Nb, Ti-10Mo-20Nb, and Ti-10Mo-30Nb alloys. Reflections from the (α\u0026rsquo;\u0026rsquo; + ω) phases were identified in the β matrix of the Ti-10Mo and Ti-10Mo-6Nb alloys. The XRD diffraction of Ti-10Mo-9Nb alloy showed only reflections from the α\u0026rsquo;\u0026rsquo;phase in the β matrix. The results showed than the microstructure change from (β\u0026thinsp;+\u0026thinsp;α\u0026Prime; + ω) \u0026rarr; (β\u0026thinsp;+\u0026thinsp;α\u0026Prime;) phases to single β phase in Ti-10Mo-20Nb and Ti-10Mo-30Nb alloys with Nb addition, showing that the Nb addition resulted in the β-phase stability. This is in accordance with the literature showing that β-phase stability in titanium alloys can be assessed using the molybdenum equivalent [Mo\u003csub\u003eeq\u003c/sub\u003e]. If the [Mo\u003csub\u003eeq\u003c/sub\u003e] value is higher than 10% [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], β phase metastable is retained during quenching from temperatures (above the β transus). Below this value, α\u0026rsquo; (hexagonal), α\u0026rsquo;\u0026rsquo;(orthorhombic) and ω phase (hcp structure) may precipitate in the β-Ti matrix. In addition, the cooling rate has a predominant role in the phases transformation in Ti alloys [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows optical micrographs of (a) Ti-10Mo, (b) Ti-10Mo-6Nb, (c) Ti-10Mo-9Nb (d) Ti-10Mo-20Nb and (e) Ti-10Mo-30Nb alloys. The adopted solution treatment could not eliminate completely the as-cast dendrite structures. This effect was more evident in the alloy with lower Nb content and is attributed to the low treatment temperature (950\u0026deg;C) and short duration. A fine acicular α\u0026rsquo;\u0026rsquo;phase was observed in the β matrix of Ti-10Mo [Mo\u003csub\u003eeq\u003c/sub\u003e = 10.0], Ti-10Mo-6Nb [Mo\u003csub\u003eeq\u003c/sub\u003e = 11.7] and Ti-10Mo-9Nb [Mo\u003csub\u003eeq\u003c/sub\u003e = 12.5] alloys, mainly on the on the Ti-10Mo alloy (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). It was verified than α\u0026rsquo;\u0026rsquo; phase decreases for higher Nb contents. It was observed only single β phase in Ti-10Mo-20Nb and Ti-10Mo-30Nb alloys.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Mechanical characterization\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e provides the measured values of hardness and elastic modulus (E) of Ti-10Mo, Ti-10Mo-6Nb, Ti-10Mo-9Nb, Ti-10Mo-20Nb, Ti-10Mo-30Nb, Ti-6Al-4V alloys and Ti (cp). The Ti-10Mo-xNb alloys showed a small variation in the hardness with Nb addition up to 9%, however with the increase in the Nb content a significant decrease was observed. This increase in Nb is related to the suppression of the α'' phase, since it is observed by the optical microscopy and XRD results shown that the Ti-10Mo alloy is the one with the highest amount of martensitic phase, followed by the Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys. The α'' martensitic phase usually leads to a decrease in hardness in the alloys [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The standard deviation observed in the Ti-10Mo alloy is much higher than for the other alloys. This is related to the phases present in the alloy and their volume. All alloys presented hardness values higher than that of Ti cp, and the Ti-10Mo, Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys presented hardness values close to those of the Ti-6Al-4V alloy.\u003c/p\u003e\u003cp\u003eThe elastic modulus values of the alloys with Ti (cp) and the Ti-6Al-4V alloy are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The Ti-10Mo, Ti-10Mo-20Nb and Ti-10Mo-30Nb alloys showed lower elastic modulus compared to Ti (cp), Ti-6Al-4V and the other alloys. On the other hand, the Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys showed a modulus similar to Ti (cp) and the Ti-6Al-4V alloy.\u003c/p\u003e\u003cp\u003eA notably low elastic modulus was obtained for Ti-10Mo-20Nb wish exhibited only β phase in its microstructure. Thid result is in agreement with previous studies of Li \u003cem\u003eet al.\u003c/em\u003e [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] who reported that the elastic modulus in Ti alloys typically follows the order ω\u0026thinsp;\u0026gt;\u0026thinsp;α\u0026thinsp;\u0026gt;\u0026thinsp;α' \u0026gt;α\" \u0026gt;β phases. The decreasing of elastic modulus of Ti-10Mo-20Nb alloy when compared with the largely used Ti-6Al-4V is around 40%. A close match between the elastic modulus of bone and the alloy is desirable, as it promotes uniform stress distribution and enhances the mechanical stability of the adjacent bone tissue.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eHardness (H) and elastic modulus (E) values of Ti-10Mo, Ti-10Mo-6Nb, Ti-10Mo-9Nb, Ti-10Mo-20Nb, Ti-10Mo-30Nb, Ti-6Al-4V alloys and Ti (cp).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAlloys\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eHardness (H)\u003c/p\u003e\u003cp\u003e(HV)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eModulus (E)\u003c/p\u003e\u003cp\u003e(GPa)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTi-10Mo\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e318.47\u0026thinsp;\u0026plusmn;\u0026thinsp;24.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e107.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTi-10Mo-6Nb\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e339.77\u0026thinsp;\u0026plusmn;\u0026thinsp;5.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e122.44\u0026thinsp;\u0026plusmn;\u0026thinsp;0.26\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTi-10Mo-9Nb\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e340.46\u0026thinsp;\u0026plusmn;\u0026thinsp;6.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e120.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.84\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTi-10Mo-20Nb\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e238.18\u0026thinsp;\u0026plusmn;\u0026thinsp;10.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e74.30\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTi-10Mo-30Nb\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e249.33\u0026thinsp;\u0026plusmn;\u0026thinsp;4.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e94.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTi-6Al-4V\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e337.31\u0026thinsp;\u0026plusmn;\u0026thinsp;15.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e123.76\u0026thinsp;\u0026plusmn;\u0026thinsp;4.41\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTi (cp)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e174.89\u0026thinsp;\u0026plusmn;\u0026thinsp;8.93\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e120.67\u0026thinsp;\u0026plusmn;\u0026thinsp;5.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe hardness-to-modulus ratio (H/E) is a key parameter in the selection of biomaterials for bone implant applications, particularly in the early stages of evaluation prior to more complex mechanical tests such as tensile and compression testing. This ratio directly affects stress distribution between the implant and the surrounding bone tissue. Higher H/E values are typically associated with improved wear resistance and a reduced risk of stress shielding, thereby helping to minimize bone resorption caused by significant stiffness mismatches between the implant material and the host bone [\u003cspan additionalcitationids=\"CR34\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents a comparison between Ti (cp), Ti alloys commonly used in biomedical applications [\u003cspan additionalcitationids=\"CR37 CR38\" citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e], and alloys from the Ti-10Mo-xNb system (x\u0026thinsp;=\u0026thinsp;0, 6, 9, 20, and 30). Among all alloys, the highest H/E ratio was obtained for the Ti-10Mo-20Nb alloy, which exhibited only the β phase in its microstructure, followed by the Ti-10Mo alloy, characterized by a microstructure composed of α\u0026rsquo;\u0026rsquo; and ω phases within the β matrix.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe electrochemical behaviour of the Ti-10Mo-xNb (x\u0026thinsp;=\u0026thinsp;0, 6, 9, 20 e 30%p Nb) in physiological saline solution is present in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e to \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The corrosion potential (E\u003csub\u003ecorr\u003c/sub\u003e) of the alloys was measured by monitoring the open circuit potential after immersion in the salt solution for 1 hour. The variation in E\u003csub\u003ecorr\u003c/sub\u003e with immersion time is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. For all the alloys evaluated, the potential starts at more negative values and tends to evolve towards higher potentials with increasing time. The corrosion potential increases continuously until approximately 1000 s, after which time it remains stable during the test. This behaviour suggests the spontaneous formation of a protective film on the surface of the alloy. The formation of a protective oxide is natural for titanium alloys, as previous studies have shown [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan additionalcitationids=\"CR41 CR42\" citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThere is a common understanding that the chemical composition of the alloy and the phases present have an influence on film formation, but this is still a matter of controversy. In the present work, two distinct behaviors were observed in relation to the corrosion potential. For the Ti-10Mo, Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys, the corrosion potential starts near E = -0.500 V (SCE) and gradually increases until it reaches a stable level at E = -0.398 V, -0.227 V and \u0026minus;\u0026thinsp;0.362 V (SCE) respectively. Ti-10Mo-20Nb and Ti-10Mo-30Nb corrosion potential begins in the most negative values, around E = -0.650V (SCE), gradually evolves to more noble potentials around E = -0.422 V for the 20%w Nb and E = -0.534 for the 30%w Nb alloy.\u003c/p\u003e\u003cp\u003eThis behaviour shows that regardless of composition, all the alloys evaluated show passive behaviour through the spontaneous formation of protective oxide.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the potentiodynamic polarization curves carried out on the Ti-10Mo-xNb alloys. The curves were obtained after stabilization of the open circuit potential, after a period of 1 hour. The results show that regardless of the chemical composition of the alloy and the phases present, all the curves show a similar behavior, typical of passive alloys. Two typical regions are observed in the polarization curves. The first (region I - active zone) is characterized by an increase in current as the potential rises to approximately E\u0026thinsp;=\u0026thinsp;0.050 V (SCE). From this potential onwards, the current stops varying and remains constant, initiating region II (passive zone), which is characterized by the formation of the passive film. The potential E\u0026thinsp;=\u0026thinsp;0.500 V was chosen to measure the passivation current (i\u003csub\u003epass\u003c/sub\u003e) characteristic of region II. Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the electrochemical parameters E\u003csub\u003ecorr\u003c/sub\u003e and i\u003csub\u003epass\u003c/sub\u003e obtained by monitoring the open circuit potential and polarization curves. The passive current density values (i\u003csub\u003epass\u003c/sub\u003e) obtained of the order between 6\u0026ndash;10 \u0026micro;A.cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. These values are close to those observed in other studies for titanium alloys with similar composition [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The results showed that increasing the Nb content in the alloy promotes the stabilization of the β phase. The alloys with the highest Nb content (20 and 30%w) show higher current density values in the passive region, indicating the formation of a less resistant oxide film compared to the films formed in the presence of the α and ω phases.\u003c/p\u003e\u003cp\u003eAlthough some authors attribute the presence of β-stabilizer elements as responsible for an increase in corrosion resistance in Ti alloys [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e], in a recent study [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] was observed that the presence of fine α-phase precipitates in the β-matrix in the Ti-5Nb-3Mo-3V-3Al-2Zr-1Fe alloy was responsible for the increase in the mechanical properties and corrosion resistance of the alloy. This explanation could be applied to understanding the electrochemical behavior of Ti-10Mo-xNb alloys. In this case, the presence of fine and homogeneous of α\u003csup\u003e\u0026rdquo;\u003c/sup\u003e precipitates resulting in an increase in the alloy's corrosion resistance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u0026ndash; Corrosion potential and corrosion current density determined from polarization curves of Ti-10Mo-20Nb, Ti\u0026ndash;12Mo\u0026ndash;13Nb and Ti-6Al-4V alloys in physiological saline solution.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAlloys\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePhases\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eE\u003csub\u003ecorr\u003c/sub\u003e (V\u003csub\u003e(SCE)\u003c/sub\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003csub\u003epass\u003c/sub\u003e (A/cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi-10Mo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eα\u003csup\u003e\"\u003c/sup\u003e\u0026thinsp;+\u0026thinsp;ω in β matrix\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.398\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.015 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi-10Mo-6Nb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eα\"+ω in β matrix\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.227\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.154 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi-10Mo-9Nb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eα\"+ω in β matrix\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.362\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7.650 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi-10Mo-20Nb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eβ matrix\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.422\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9.957 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi-10Mo-30Nb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eβ matrix\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.534\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.077 x 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe chronoamperometry assays presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e provide insight to understand the behavior of the passive film under different potential conditions. The results show the current transients as a function of time, obtained for the Ti-10Mo-xNb alloys at a fixed potential of\u003c/p\u003e\u003cp\u003eE\u0026thinsp;=\u0026thinsp;1.6V. This potential enables the evatuation of whether the film remains intact at higher potentials than those applied during potentiodynamic polarization tests, allowing assessment of the film\u0026rsquo;s integrity under more aggressive electrochemical conditions. The transient profiles one-hour period shows a drop in current in the initial moments (~\u0026thinsp;500 s), after which the values remain stable for the rest of the experiment. This behavior clearly demonstrates the formation of the passive film on the surface of all the samples studied, regardless of the Nb content in the Ti-10Mo alloy. Similar behavior was observed by [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] when evaluating the effect of adding Ga to Ti-45Nb alloys. The authors related the drop in current response to the formation of a stable, compact and protective passive film during sample polarization.\u003c/p\u003e\u003cp\u003eHowever, although all the alloys show the formation of a passive film that remained stable throughout the test period, it is worth noting that the formation of this film occurs more quickly for the Ti-10Mo and Ti-10Mo-6Nb alloys. Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the current response obtained for the times of 250 s and 3600 s (end of the test). The results clearly show that the passive film forms more easily for samples with the lowest niobium content. This behavior indicates that, although the addition of niobium does not hinder the formation and stability of the passive film, there appears to be an optimum concentration (0\u0026ndash;6% Nb) that promotes faster oxide growth upon exposure to the physiological solution.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cb\u003e\u0026ndash; Current density determined from Chronoamperometry curves of Ti-10Mo-20Nb, Ti\u0026ndash;12Mo\u0026ndash;13Nb and Ti-6Al-4V alloys in physiological solution of 0.9% NaCl naturally aerated.\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAlloys\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePhases\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eI\u003csub\u003e250s\u003c/sub\u003e (A/cm\u003csup\u003e2\u003c/sup\u003e\u003csub\u003e)\u003c/sub\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003csub\u003e3600s\u003c/sub\u003e (A/cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi-10Mo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eα\u0026rsquo;\u0026rsquo;+ω in β matrix\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9.45 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.97 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi-10Mo-6Nb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eα\u0026rsquo;\u0026rsquo;+ω in β matrix\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9.15 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.51 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi-10Mo-9Nb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eα\u0026rsquo;\u0026rsquo;+ω in β matrix\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.40 x 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7.09 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi-10Mo-20Nb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eβ matrix\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.75 x 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e8.13 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi-10Mo-30Nb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eβ matrix\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.18 x 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.65 x 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eIn the present work, all the Ti-10Mo-xNb alloys evaluated showed high corrosion resistance, due to the spontaneous formation of the titanium oxide film, and this behavior is evident in the evolution of the corrosion potential. However, the polarization curves and chronoamperometry tests showed that for Nb content\u0026thinsp;\u0026gt;\u0026thinsp;6% the corrosion resistance tends to decrease.\u003c/p\u003e\u003cp\u003eAlthough numerous studies (e.g., [references]) have reported that the addition of Nb enhances the corrosion resistance of Ti alloys, recent investigations [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] have observed that the presence of ω-phase and α\u003csup\u003e\u0026rdquo;\u003c/sup\u003e- martensitic precipitates can further promote the development of more protective passive films. Similarly, the results obtained in the present study show that the presence of fine α\u0026rsquo;\u0026rsquo;- phase precipitates exert a more effective influence over the beneficial effect of Nb incorporation on corrosion resistance, within the evaluated experimental conditions.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. CONCLUSION","content":"\u003cp\u003eThe microstructural characterization results of the Ti-10Mo-xNb (x\u0026thinsp;=\u0026thinsp;0, 6, 9, 20, and 30) alloys showed than the microstructure change from β\u0026thinsp;+\u0026thinsp;α\u0026Prime;+ω \u0026rarr; β\u0026thinsp;+\u0026thinsp;α\u0026Prime; phases to single β phase in Ti-10Mo-20Nb and Ti-10Mo-30Nb alloys with Nb addition, showing that the Nb addition resulted in the β-phase stability.\u003c/p\u003e\u003cp\u003eAll alloys presented hardness values higher than that of Ti (cp), and the Ti-10Mo, Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys presented hardness values close to those of the Ti-6Al-4V alloy. The alloys Ti-10Mo, Ti-10Mo-20Nb and Ti-10Mo-30Nb alloys showed lower elastic modulus compared to Ti (cp), Ti-6Al-4V alloys. On the other hand, the Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys showed a modulus similar to Ti (cp) and the Ti-6Al-4V alloy. The lower elastic modulus of designed alloys was obtained for Ti-10Mo-20Nb than presented only β phase in the microstructure.\u003c/p\u003e\u003cp\u003eAmong all the alloys, the highest H/E ratio was obtained for the Ti-10Mo-20Nb alloy, which exhibited only the β phase in its microstructure, followed by the Ti-10Mo alloy, characterized by a microstructure composed of α and ω phases within the β matrix.\u003c/p\u003e\u003cp\u003eThe corrosion resistance of the Ti-10Mo-xNb alloys was evaluated through electrochemical assays. All the alloys exhibited high corrosion resistance, mainly related to the formation of the titanium oxide film, which enables the alloy to be passivated and protected. It was observed that the addition of niobium to the Ti-Mo alloy promotes improvements in the quality of the passive film, as evidenced by the more noble corrosion potential and lower passivation current. However, at contents higher than 6% Nb, the corrosion resistance tends to decrease.\u003c/p\u003e\u003cp\u003eThe combination of electrochemical and mechanical results indicates that, among the alloys evaluated, Ti-10Mo is the one that presents the best combination of results. However, the Ti-10Mo-20Nb alloy should be taken into consideration because it has the lowest modulus of elasticity and good corrosion resistance.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eS. B. : Main manuscript textA. I.C.S: Corrosion test.C.M.F.A.C: Corrosion test.A.R.V.N.: Microstructural characterizationM.C.R: Mechanical characterizationW.C.L.P: Corrosion test.C.A.N.: Results discussion.J.D.: Microstructural characterization.L.H.A.: manuscript revision.\u003c/p\u003e\u003ch2\u003eACKNOWLEDGMENT\u003c/h2\u003e\u003cp\u003eThis work was supported by the Brazilian Agencies CNPq, FAPERJ and CAPES.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eGunawarman B, Niinomi M, Akahori T, Takeda J, Toda H. Mechanical properties of Ti-4,5Al-3V-2Mo-2Fe and possibility for healthcare applications. Mater Sci Engineering: C. 2005;25:296\u0026ndash;303.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eOliveira NTC, Guastaldi AC. Electrochemical behavior of Ti-Mo alloys as biomaterial. Corros Sci. 2008;50:938\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhou YL, Niinomi M, Akahori T. 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Sci Rep. 2024;14:31390.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"in-vitro-models","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [In vitro models](https://link.springer.com/journal/44164)","snPcode":"44164","submissionUrl":"https://submission.springernature.com/new-submission/44164/3","title":"In vitro models","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Ti-Mo-Nb alloys, Corrosion, mechanical properties, biomaterial, Microstructure","lastPublishedDoi":"10.21203/rs.3.rs-8195494/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8195494/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eβ-Ti alloys are gaining space in biomedical applications due their favorable combination of mechanical properties including their low elastic modulus and corrosion resistance. In this context, β titanium Ti-10Mo-xNb (x\u0026thinsp;=\u0026thinsp;0, 6, 9, 20 and 30wt%) alloys were designed and produced. The relationship among the alloy composition, microstructure, and corrosion properties was investigated. The results were compared with those of the commercial Ti-6Al-4V and Ti(cp) alloys. Results showed that with increasing Mo equivalent, the contents of the α\u0026rsquo;\u0026rsquo; and ω phases decreased, while the content of the β phase increased accordingly. The produced Ti-10Mo-xNb alloys exhibited hardness values higher than commercially pure Ti (cp). Among them the Ti-10Mo, Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys showed hardness values comparable to Ti-6Al-4V alloy. Furthermore, each alloy exhibited a lower elastic modulus than Ti-6Al-4V, with Ti-10Mo-20Nb (74 GPa) and Ti-10Mo-30Nb (94 GPa) showing significantly reduced values. All the Ti-10Mo-xNb alloys exhibited high corrosion resistance, attributed to the formation of a passive film after exposure to the physiological saline solution. The corrosion properties were evaluated using potentiodynamic polarization curves and chronoamperometry. Alloys with lower Nb contents (0 and 6%) exhibited relatively higher corrosion resistance, whereas those with higher Nb content showed reduced effectiveness of the protective film. This behavior can be related to the presence of fine α\u0026Prime;-phase precipitates distributed within the matrix of the Ti-10Mo and Ti-10Mo-6Nb alloys. The Ti-10Mo-20Nb alloy, however, exhibits the most favorable overall balance, combining the lowest elastic modulus with high corrosion resistance.\u003c/p\u003e","manuscriptTitle":"Influence of Mo equivalent in the corrosion resistance of Ti-10Mo-xNb alloys","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-12 18:59:01","doi":"10.21203/rs.3.rs-8195494/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-02-03T12:17:00+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"284744480808966812285464882460173359887","date":"2026-02-02T09:17:19+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-29T02:06:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"37080743442146484994133209474300753953","date":"2026-01-23T01:20:54+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-17T16:10:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"173213627384951460237506118440143872751","date":"2025-12-11T22:21:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"237599588621306365434121589339817491269","date":"2025-12-09T15:57:22+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-06T21:02:35+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-28T15:27:29+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-11-25T05:26:33+00:00","index":"","fulltext":""},{"type":"submitted","content":"In vitro models","date":"2025-11-24T16:10:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"in-vitro-models","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [In vitro models](https://link.springer.com/journal/44164)","snPcode":"44164","submissionUrl":"https://submission.springernature.com/new-submission/44164/3","title":"In vitro models","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"133bb2ef-2c5f-472c-af5a-ba15033ee4e3","owner":[],"postedDate":"December 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-16T18:08:18+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-12 18:59:01","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8195494","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8195494","identity":"rs-8195494","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}