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Titanium and its alloys are commonly utilized in the biomedical field for fabricating orthopedic and dental implants due to their favorable mechanical, chemical, and biological properties. However, titanium alloys exhibit limited or no bioactivity, necessitating the application of surface functionalization techniques to enhance their functional characteristics suitable for biomedical applications. Plasma Electrolytic Oxidation (PEO) treatment is a simple and versatile surface modification process for valve metals that can add superior osseointegration and bioactive properties to titanium and its alloys. Therefore, this review aims to summarize the mechanisms involved in obtaining porous coatings on the surface of titanium alloys using the PEO method, as well as to outline some of the physicochemical and biological properties of the resulting surfaces. The article discusses the mechanisms of action of bactericidal agents such as copper, silver, and zinc, commonly incorporated into PEO coatings. Finally, the study concludes by discussing remaining challenges and future perspectives that need to be addressed.

Despite β-type Ti alloys achieving a low elastic modulus, metallic implants generally exhibit poor wear resistance. To address this issue, in-situ Ti-based matrix composites (TMCs) are considered due to their strong bonding at the matrix/reinforcement interface. While TiC particles and TiB whiskers are common reinforcements for in-situ TMCs, limited research combines their effects with the low elastic modulus of Ti alloys. Here, we present a novel approach using arc-melting on Ti–40Nb alloy with 5 vol% additions of NbC, NbB2, and B4C. Respectively, three TMCs were obtained with the β-type Ti–Nb matrices reinforced individually with TiC particles, TiB whiskers, and hybridized with both. The produced TMCs exhibited the same passive behavior of the unreinforced Ti–40Nb alloy. However, tribocorrosion resistances were improved, as TMCs achieved nobler potentials during sliding than the unreinforced alloy (−0.5 and −0.9 V, respectively). Notably, the TiB-reinforced and the hybrid reinforced TMCs displayed minimal wear damage, while the TiC-reinforced TMC achieved a remarkable low elastic modulus of approximately 73 GPa. This study introduces promising alternatives for wear-resistant load-bearing implant applications.

This study aims to promote the growth of a porous oxidized coating of TiO2 due to oxidation of the surface of the Ti–Nb alloy substrates (Nb = 5, 10, and 25 wt%) using the micro-arc oxidation (MAO) technique. Using structural (x-ray diffraction) and microstructural (optical, confocal, and scanning electron microscopy) characterization techniques, it was observed that Nb promotes the formation of the β phase in Ti alloys, reducing Vickers microhardness and elastic modulus values. Regarding the MAO coating, the results showed that the TiO2 coatings are in the form of anatase and rutile, where Nb promotes the formation of the rutile phase, increasing the hardness of the coatings. MAO coatings have high roughness values due to the formation of porous structures characteristic of MAO surfaces. Adhesion results show that MAO coatings have low adhesion with the substrate.

The main objective of this study was to produce two new biomedical alloys, Ta-(75-x)Ti-xZr (x = 25, 50 wt%), and to carry out a detailed analysis of the crystal structures, phase composition, lattice parameters, hardness, and elastic modulus of the alloys under the influence of heat treatments. After melting (as-cast condition), the two alloys were subjected to two heat treatments carried out at a temperature of 1000 °C: one with slow cooling in the oven (SC) and the other rapidly cooled with ice water (RC). From the structural and microstructural characterizations (XRD, SEM, and Rietveld), it was observed that the Ta-(75-x)Ti-xZr produced are α+β type alloys. However, the Ta–25Ti–50Zr alloy contains a more significant amount of β phase due to the β stabilizing action of Zr combined with Ta as a typical β stabilizing element. Regarding the cooling after heat treatments, rapid cooling (RC) promoted the formation of the metastable α'' phase, and heat treatment followed by slow cooling (SC) promoted the formation of the α+β phases. The alloys’ hardness, elastic modulus, and atomic packing factor (APF) were affected by changes in the α and α'' phases fraction. The SC treatment increased APF, hardness, and elastic modulus, while the RC treatment decreased elastic modulus, optimizing it for biomedical applications.

The main objective of this paper is to produce an anodic layer of TiO2 rich in calcium, phosphorus, and magnesium using the anodizing technique known as micro-arc oxidation (MAO) on the Ti-25Ta alloy together with the incorporation of silver (Ag), copper (Cu) and zinc (Zn) metallic ions using different electrolytes. The structural changes and microstructures on the MAO surfaces were analyzed using the X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). The chemical composition to verify whether silver, copper, and zinc were incorporated via energy dispersive spectroscopy (EDS) and surface characteristics such as wettability and hardness of the coatings were also investigated. From the EDS mapping results, it is observed that the MAO process was effective in incorporating the ions present in the electrolyte. Regarding X-ray diffraction patterns, the TiO2 phases formed in the Ti-25Ta alloy has a mixture of anatase and rutile, making the MAO surface hydrophilic. The Ag element surface is thicker than the films containing Cu and Zn, as the Ag ions have high electrical conductivity, accelerating the oxidation process during surface treatment. Regarding hardness, coating containing Cu have a higher hardness value.

This study delves into the comprehensive characterization of the Ti–25Ta-xNb alloy system, whith a focus on its potential biomedical applications. Int intriguing insights into these alloys properties were unveiled through a systematic investigation encompassing EDS analysis, density measurements, chemical mapping, X-ray diffraction, microstructural examination, and microhardness assessments. The chemical composition results confirm that these alloys exhibit the appropriate stoichiometries, with the melting process yielding homogeneous compositions. Notably, the Ti–25Ta–10Nb and Ti–25Ta–20Nb alloys showcase the coexistence of α and β phases, while those with 30 % and 40 % Nb consist solely of the β phase, highlighting the β-stabilizing role of Nb and Ta. These results align seamlessly with X-ray diffractograms, Rietveld refinement data, and microstructural observations. The analysis further reveals a decrease in edges B and C of the α'' structure, consistent with previous literature, indicating the alloys sensitivity to Nb additions. In terms of hardness, a discernible trend emerges with the stabilizing of the β phase, leading to reduced hardness values, as anticipated. Excitingly, not all alloys in the Ti–25Ta-xNb system exhibited cytotoxic effects, while they facilitated the crucial process of cell adhesion. This presents a promising prospect for their application in biomaterials. Among the developed alloys, the Ti–25Ta–30Nb alloy stands out due to its proximity to pure titanium in terms of hardness and its potential to promote cell proliferation.These findings underscore the potential of the Ti–25Ta-xNb alloy system for biomedical applications, provided that further studies optimize their suitability for such purposes.

This study primarily focuses on analyzing anelastic processes due to interstitial oxygen in the Ti–25Ta–40Zr alloy. From the structural and microstructural characterization (DRX and optical microscopy), it was detected that the Ti–25Ta–40Zr alloy is a α + β type. Peaks of anelastic relaxation were visualized in the Ti–25Ta–40Zr alloy, where the peaks are thermally activated, with the shift of Qp−1 to higher temperatures in tests performed at high frequencies. The activation energy (E), relaxation time (τ0), and diffusivity (Do) of oxygen in the alloy were obtained E = (0.49 ± 0.02) eV, τ0 = (6.3 ± 0.2) x10−19 s and D0 = (5.0 ± 0.1) x10−3 m2/s.

Surface treatments are widely used techniques to improve the wear resistance of titanium alloys for biomedical applications. Modification by micro-arc oxidation (MAO) creates an oxide ceramic coating of alloy substrate to improve wear resistance. This work investigated the micro-abrasive wear by ball cratering of MAO coatings over Ti–25Ta alloy. For this purpose, the surfaces were worn by steel balls at a load of 2 N and a rotation speed of 200 rpm. After 50 min of testing, the depth of the wear reaches the substrate, confirming that the MAO coating has a much lower wear rate. Guided by Archard's law, the wear volume, wear rate, and MAO coating thickness were calculated through wear test.

This work aims to modify the surface of the Ti–25Ta-xZr (x = 0, 25, and 50 wt%) system alloys through micro-arc oxidation (MAO) to incorporate calcium, phosphorus, and magnesium ions in the oxidized layer deposited. The MAO surface modification was performed by changing the limited voltage applied to system (200, 250, and 300V). Structural characterizations by X-ray diffraction and X-ray photoelectron spectroscopy showed that the formed MAO coatings comprise TiO2, Ta2O5, ZrO2, and CaCO3 oxides. Voltage inhibits the formation of Ta2O5 and CaCO3 phases and decreases the incorporation capacity of Ca, P and Mg ions. The MAO coatings' topography, thickness, and roughness, analyzed by scanning electron microscopy and confocal microscopy techniques, showed that increasing the voltage tends to increase pore sizes and reduces film thickness; conversely, it decreases the number of pores per μm2. Regarding hardness and elastic modulus, adding Zr increases the MAO coating's hardness due to the formation of ZrO₂. However, increasing the voltage decreases the MAO coatings' hardness due to the formation of the compound CaCO3. The MAO process increased the elastic modulus of the Ti–25Ta-xZr bulk alloys. Finally, the adhesion of the films was analyzed by the Rockwell-C adhesion test. The results showed a good adhesion of MAO coatings to Ti–25Ta-xZr substrates.

The main objective is to carry out several heat treatments to change the phases and some characteristics of the MAO coatings formed in Ti–25Ta–25Zr alloy in order to understand how the oxides or morphology of the MAO coating influence hardness, elastic modulus, adhesion, and wear resistance. The results showed that the MAO coating is amorphous and constituted by TiO2, ZrO2, Ta2O5, and CaCO3, and the heat treatments promoted the formation of Ti2O3 and CaO and the degradation of Mg at 800 °C. Increasing the temperature of the heat treatments reduced the pore size and, consequently, decreased roughness (minimum value of 0.77 μm in the condition of 500 °C), increased hardness (maximum of 673 HV), and improved wear resistance (3 × 10−15 m/N−1). When heat treatments are carried out above 600 °C, cracks are observed throughout the coating. Under these conditions, the roughness is altered and is no longer influenced only by pores size. Cracks increase the roughness of the coatings, reaching a maximum value of 1.16 μm. Therefore, there is a decrease in the coatings’ hardness, and the alloy becomes more sensitive to abrasive wear phenomena. At 800 °C, the hardness is 494 HV, and the wear rate ∼40 × 10−15 m2/N Regarding elastic modulus, the Ti–25Ta–25Zr alloy with the MAO coating subjected to heat treatment at 400 °C has a lower elastic modulus. Coatings subjected to high temperatures (above 500 °C) have an HF1 rating indicating high adhesion.

The objective of this study is to analyze the influence of the heat treatment temperature carried out at ultra-high vacuum on surfaces formed in the Zr-25Ta-25Ti alloy by the micro-arc oxidation (MAO) technique to produce a ceramic layer with high hardness and high wear resistance. The results of structural (XRD) and microstructural characterization (SEM, optical and confocal microscopy technique) show that the surfaces are mainly composed of zirconium dioxide (ZrO2), Ti2ZrO, and calcium oxide (CaO). The heat treatments at high temperatures (500–800 °C) altered the phases of the MAO coating, forming ZrC. Confocal images showed that increasing temperature increased the roughness of the coatings (0.65 → 1.06 μm). Consequently, the topography of the coatings, wettability, microhardness (Vickers), and wear resistance (obtained by the ball cratering technique) of the materials are also modified. The wear results show that the MAO coating has a low wear rate value due to the MAO surfaces’ high hardness, efficiently protecting the substrates of the Zr-25Ta-25Ti alloy against tribological phenomena. Finally, the increase in heat treatment temperature promoted the formation of cracks in the coatings due to the difference in thermal expansion of the MAO ceramic with the Zr-25Ta-25Ti alloy substrate, causing a decrease in the hardness value and reducing wear resistance.

New Ti alloys are being developed to obtain materials with better properties for biomedical applications. In order to avoid complications caused for the presence of Al and V ions in the blood stream, novel alloys have been developed without these two elements. Mo and Nb are two non-toxic β-stabilizing elements used in Ti alloys because they decrease the elastic modulus and improve corrosion resistance. Thus, this study investigated the influence of Nb addition in Ti-xNb-5Mo alloy (x = 0, 10, 20, 30 %wt) on microstructure, structure, and selected mechanical properties. The samples were characterized after annealing, and the results showed the decrease of α phase and growth of β phase with the addition of Nb. The ω phase in the alloy containing 20% Nb was also detected. The samples’ elastic modulus and microhardness tended to decrease with increasing of the β phase, except for the Ti–20Nb–5Mo alloy due to phase hardening ω. The average crystallite size of the α and β phases increased with the addition of Nb.

This paper aims to analyze the structure of the Ti-25Ta-xZr system alloys (x = 0, 10, 20, 30, and 40% wt.) after melting and hot-rolling by Rietveld's technique. The results confirm that zirconium acts as a β phase stabilizer (in which the Ti-25Ta-40Zr alloy is fully β in the as-cast condition), increases the lattice parameters of the phases, decreases the c/a ratio of the α phase, consequently, decreases the elastic modulus values (86 to 72GPa) and decreases the atomic packing factor (APF) of the alloys (60% reduction compared to alloys with and without zirconium in the as-cast condition and 50% reduction in the hot-rolled condition). Concerning hot-rolling, this mechanical process induces the α phase formation and increases the atomic packing factor of the alloys (APF). By the William-Hall technique, it was possible to calculate the average crystalline size and the micro-strain of the structures.

Abstract Ti and its alloys are the most used metallic biomaterials devices due to their excellent combination of chemical and mechanical properties, biocompatibility, and non-toxicity to the human body. However, the current alloys available still have several issues, such as cytotoxicity of Al and V and high elastic modulus values, compared to human bone. β-type alloys, compared to α-type and (α + β)-type Ti alloys, have lower elastic modulus and higher mechanical strength. Then, new biomedical β-type alloys are being developed with non-cytotoxic alloying elements, such as Mo and Nb. Therefore, Ti-5Mo-xNb system alloys were prepared by argon arc melting. Chemical composition was evaluated by EDS analysis, and the density measurements were performed by Archimedes' method. The structure and microstructure of the alloys were obtained by X-ray diffraction and optical and scanning electron microscopy. Microhardness values were analyzed, and MTT and crystal violet tests were performed to assess their cytotoxicity. As the Nb concentration increases, the presence of the β-Ti phase also grows, with the Ti-5Mo-30Nb alloy presenting a single β-Ti phase. In contrast, the microhardness of the alloys decreases with the addition of Nb, except the Ti-5Mo-10Nb alloy, which has its microhardness increased probably due to the ω phase precipitation. Biological in-vitro tests showed that the alloys are not cytotoxic.

Ultrasonic velocity and attenuation measurements of a commercially available Ni-rich polycrystalline Ni–Ti alloy were simultaneously obtained upon cooling from room temperature (RT) down to 130 K. The anelastic spectra show multiple anomalies in both velocity and attenuation curves, which evidence a complex nature of structural rearrangements exhibited by Ni–Ti alloy, associated with relaxations and phase transformations. In particular, some evident anomalies at 285 and 180 K, not previously exploited using ultrasonic measurements on Ni-rich polycrystalline Ni–Ti alloy, were associated with austenite to pre-martensitic (B2 → R) and pre-martensitic to martensitic (R → B19’) phase transitions, respectively. The peculiar temperature separation between these transformations was interpreted based on chemical composition and the Ni–Ti alloy microstructure evolution. X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were also used to add complementary results about phase transformations and thermal events exhibited by Ni–Ti alloy at low temperatures. XRD, Rietveld refinement, SEM and transmission electron microscopy (TEM) analyses confirm the coexistence of the austenite B2, martensite B19’, and Ni4Ti3 phases at RT. DSC measurements indicated reversible two-stage martensitic transitions involving B2 ↔ R ↔ B19’ phase transformations at similar temperatures than the observed from ultrasonic anomalies. Besides that, several anelastic relaxation events identified around the phase transitions reveal the occurrence of complex physical mechanisms, such as accommodation of the twinned R-phase and martensite domain walls, twinning boundaries mobility, and the coupling between stress-induced dislocation motion and interstitial diffusion, not reported simultaneously in the literature. The ferroelastic nature of martensite and pre-martensite phase transformations was confirmed for a commercially available Ni-rich polycrystalline Ni–Ti alloy studied in this work.

Due to their lower cost and good mechanical and corrosion properties, ferrous materials such as stainless steel (SS) are commonly used as bio-materials, mainly as surgical instruments and implants. Surface treatments such as plasma electrolytic oxidation (PEO) can be a valuable tool to increase corrosion resistance and enhance the bio-compatibility of metallic materials. In this scenario, the current study evaluated the effect of electrolyte composition on the surface of SS304 submitted to PEO treatment. The variation in the amount of KOH and Ta(OH)5 promoted significant changes in the surface characteristics, forming Fe-rich oxide plates, Ta-rich agglomerate particles, and an exposed substrate. The PEO-treated substrates were depleted of some alloying elements (Cr, Ni, and Mn), which, allied to the Ta-enrichment, affected the roughness, wettability, phase stability, micro-hardness, and corrosion resistance. All the PEO treatments presented a phase composition of single γ-Fe instead of a dual α + γ phase from the untreated substrate, which was understood in terms of the Nieq-Creq diagram. The corrosion tests indicated that the PEO treatment significantly affected the corrosion parameters, having the presence of a non-uniform oxide layer. The findings show that it is possible to control the chemical and phase composition of SS304 material employing PEO treatment.

This study aimed to produce Ti-15Nb alloy with a low elastic modulus, verify its biocompatibility, and determine whether the alloy indirectly influences cellular viability and morphology, as well as the development of the osteogenic phenotype in cells cultured for 2, 3, and 7 days derived from rat calvarias. Two heat treatments were performed to modify the mechanical properties of the alloy where the Ti-15Nb alloy was heated to 1000 °C followed by slow (−5 °C/min) (SC) and rapid cooling (RC). The results of structural and microstructural characterization (XRD and optical images) showed that the Ti-15Nb alloy was of the α + β type, with slow cooling promoting the formation of the α phase and rapid cooling the formation of the β phase, altering the values for the hardness and elastic modulus. Generally, a more significant amount of the α phase in the Ti-15Nb alloy increased the elastic modulus value but decreased the microhardness value. After the RC treatment, the results demonstrated that the Ti-15Nb alloy did not present cytotoxic effects on the osteogenic cells. In addition, we did not find variations in the cell quantity in the microscopy results that could suggest cell adhesion or proliferation modification.

This study produced non-equiatomic TiNbZrTaMn and TiNbZrTaMo high entropy alloy (HEAs) by argon arc-melting and heat-treated for microstructural homogenization. The phase composition, microstructure, and selected mechanical properties were measured and compared with theoretical predictions. Additionally, electrochemical and cytotoxicity tests evaluated their potential applicability for use as biomaterials. X-ray diffraction measurements patterns showed a single BCC phase for the TiNbZrTaMn and a secondary HCP phase for the TiNbZrTaMo sample. The microstructural analysis revealed the formation of irregular grain boundaries and some lamellae formation, with chemical segregation of the alloying elements at the sub-micro-scale. The samples exhibited elastic modulus (80–110 GPa) closer to CP-Ti grade 2 (100 GPa) and higher Vickers microhardness (450–550 HV) than Ti–6Al–4V alloy (400 HV). The electrochemical and biological tests indicated a superior corrosion resistance against 0.9% NaCl solution compared with commercial metallic biomaterials, with proper cell adhesion and viability of pre-osteoblastic cells and hydrophilic behavior. Altogether, the data indicate that TiNbZrTaMn depicts better applicability potential for being used as a biomaterial in biomedical applications than some commercial materials (SS 316L, CP-Ti grade 2, and Ti–6Al–4V), mainly considering load-bearing orthopedical implants.

Abstract Purpose The aim of this study was to investigate the response of osteogenic cell lineage and gingival fibroblastic cells to different surface treatments of grade IV commercially pure Titanium (cpTi) disks. Material and methods Grade IV cpTi disks with different surfaces were produced: machined (M), sandblasting (B), sandblasting and acid subtraction (NP), and hydrophilic treatment (ACQ). Surface microtopography characteristics and chemical composition were investigated by scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDS). Adhesion and proliferation of SC-EHAD (human surgically-created early healing alveolar defects) and HGF-1 (human gingival fibroblasts) on Ti disks were investigated at 24 and 48 h, and osteogenic differentiation and mineralization were evaluated by assessing alkaline phosphatase (ALP) activity and alizarin red staining, respectively. Results No significant differences were found among the various surface treatments for all surface roughness parameters, except for skewness of the assessed profile (Rsk) favoring M (p = 0.035 ANOVA). M disks showed a slightly higher (p > 0.05; Kruskal-Wallis/Dunn) adhesion of HGF-1 (89.43 ± 9.13%) than SC-EHAD cells (57.11 ± 17.72%). ACQ showed a significantly higher percentage of SC-EHAD (100%) than HGF-1 (69.67 ± 13.97%) cells adhered at 24 h. SC-EHAD cells expressed increased ALP activity in osteogenic medium at M (213%) and NP (235.04%) surfaces, but higher mineralization activity on ACQ (54.94 ± 4.80%) at 14 days. Conclusion These findings suggest that surface treatment influences the chemical composition and the adhesion and differentiation of osteogenic cells in vitro. Clinical relevance Hydrophilic surface treatment of grade IV cpTi disks influences osteogenic cell adhesion and differentiation, which might enhance osseointegration.

Abstract Titanium is one of the most utilized metals for orthopedic implants. This element has excellent mechanical and biological properties. As a strategy to develop a new system of alloys that do not cause health problems to the patient, such as the Ti-6Al-4V alloy, a new group of alloys has been designed to meet these expectations. Molybdenum, when associated with titanium, reduces the transition temperature from α to the β phase. Zirconium increases the corrosion resistance, decreases the melting point, and improves the alloy's biocompatibility. The alloys with the beta phase's predominance are the most desirable for biomedical applications due to their higher mechanical compatibility with the bone tissue. This paper presents the preparation of as-cast Ti-10Mo-xZr (x= 30, 40, and 50 wt%) alloys and their characterization by measurements of density, energy dispersive spectrometry (EDS), x-ray diffraction, optical and scanning electron microscope (SEM). The density values were higher than that of pure titanium due to the zirconium and molybdenum. The EDS measurements reveal a suitable stoichiometry of the elements and no impurities contamination. In the x-ray diffraction and microscopy measurements, it was observed only peaks of the beta phase. This new system of Ti-alloys is promising for biomedical applications.

Titanium alloys are widely used in the biomedical field due to their good corrosion resistance, high mechanical strength/density ratio, low elastic modulus, and good biocompatibility. With the addition of β-stabilizers elements (such as tantalum), the decrease of the elastic modulus and excellent corrosion resistance are obtained. Zirconium despite being a neutral element appends a good corrosion resistance to titanium alloys. In this paper, Ti-25Ta-10Zr alloy was prepared and characterized aiming biomedical applications. Structural and microstructural analysis corroborated each other and showed the presence of characteristic peaks of three crystalline structures, hexagonal (α phase) and orthorhombic (α’’ phase), dissolved in a matrix with body-centered cubic crystalline structure (β phase). In the indirect cytotoxicity test, no cytotoxic effects were observed on the produced alloy. Keywords: Ti alloys, Microstructure, Biomaterials

The development of new β-Ti alloys has been extensively studied in the medical field in recent times due to their more suitable mechanical properties, such as a relatively low Young’s modulus. This paper analyzes the influence of heat treatments (homogenization and annealing) and hot rolling on the microstructure, phase composition, and some mechanical properties of ternary alloys of the Ti-xNb-5Mo system, with an amount of Nb varying between 0 and 30 wt%. The samples are produced by argon arc melting. After melting, the samples are homogenized at 1000 °C for 24 h and are hot rolled and annealed at 1000 °C for 6 h with slow cooling. Structural and microstructural analyses are made using X-ray diffraction and optical and scanning electron microscopy. Mechanical properties are evaluated by Vickers microhardness and Young’s modulus. The amount of β phase increases after heat treatment and reduces after hot rolling. The microhardness and Young’s modulus of all heat-treated samples decrease when compared with the hot rolled ones. Some samples exhibit atypical Young’s modulus and microhardness values, such as 515 HV for the as-cast Ti-10Nb-5Mo sample, indicating the possible presence of ω phase in the microstructure. The Ti-30Nb-5Mo sample suffers less variation in its phase composition with thermomechanical treatments due to the β-stabilizing effect of the alloying elements. The studied mechanical properties indicate that the annealed Ti-30Nb-5Mo sample has potential for biomedical applications, exhibiting a Young’s modulus value of 69 GPa and a microhardness of 236 HV.

With the increase in the world’s population, the rising number of traffic accidents, and the increase in life expectancy, the need for implants, dental work, and orthopedics is growing ever larger. Researchers are working to improve the biomaterials used for these purposes, improve their functionality, and increase the human body’s life span. Thus, new titanium alloys are being developed, usually with β-stabilizer elements (which decrease the elastic modulus), with the Ti-Mn-Mo alloys being one example of these. This study of the Ti-5Mn-10Mo and Ti-5Mn-15Mo alloys only showed signs of the β phase in the structure and microstructure, presenting a combination of low modulus of elasticity and high corrosion resistance compared to the values of commercial alloys. In this sense, this work presents an analysis of the influence of some thermomechanical treatments, such as homogenization, hot-rolling, solution, and annealing, on the structure, microstructure, and selected mechanical properties of the Ti-5Mn-10Mo and Ti-5Mn-15Mo alloys.

Ti alloys are the most used metallic materials in the biomedical field due to their excellent biocompatibility associated with good corrosion resistance in body fluids and relatively low elastic modulus. However, the alloys used in the orthopedic area have an elastic modulus that is 2 to 4 times higher than that of human cortical bone. Searching for new alloys for biomedical applications and with low elastic modulus, zirconium gained prominence due to its attractive properties, especially its biocompatibility. The purpose of this paper is to present novel as-cast alloys of the Zr-25Ta-xTi system and analyze the influence of titanium on the structure, microstructure, microhardness, and elastic modulus of the alloys. The alloys were prepared using an arc-melting furnace. X-ray diffraction measurements and microscopy techniques were used to characterize the crystalline structure and microstructure. From structural and microstructural characterizations, it was observed that titanium acted as an α-stabilizing element since its increase in the precipitation of the orthorhombic α” phase, an intermediate phase from β to α phases, in the alloys. Regarding microhardness measurements, the alloys have higher hardness than pure zirconium due to solid solution hardening that detaches the Zr-25Ta alloy, which has a high hardness value of the precipitation of the ω phase. Among the studied alloys, the Zr-25Ta-25Ti alloy is highlighted, demonstrating the lowest result of modulus of elasticity, which is approximately 2 times higher than the human cortical bone, but many alloys used in the biomedical field, such as pure titanium, have elastic modulus values almost 3 times higher than that of human bone.

In this paper, the effect of substitutional Mo amounts in internal friction and interstitial diffusion mechanisms was analyzed in Ti-15Zr-based alloys. Mechanical spectroscopy was obtained from room temperature up to 730 K with frequencies between 1 Hz and 40 Hz. Internal friction spectra were composed by anelastic relaxation peaks in β-type alloys (metastable and stable), due to stress-induced ordering of oxygen and nitrogen interstitially in octahedral sites of the bcc crystalline structure. Peak decomposition analysis exhibited interactions between matrix-interstitial (Ti-O and Ti-N), substitutional-interstitial (Zr-O, Mo-O and Mo-N), and clusters (Ti-O-O and Zr-O-O). The diffusion results showed that the introduction of Mo facilitates the diffusion of interstitial elements in the metallic matrix.

Abstract High levels of shrinkage stress caused by volumetric variations during the activation process are one of the main problems in the practical application of composite resins. Objective The aim of this study is to reduce the shrinkage stress and minimize the effects caused by composite resin volumetric variation due to the photopolymerization. In this way, this work proposes a systematic study to determine the optimal dimming function to be applied to light curing processes. Material and Methods The study was performed by applying mathematical techniques to the optimization of nonlinear objective functions. The effectiveness of the dimming function was evaluated by monitoring the polymerization shrinkage stress during the curing process of five brands/models of composites. This monitoring was performed on a universal testing machine using two steel bases coupled in the arms of the machine where the resin was inserted and polymerized. The quality of the composites cured by the proposed method was analyzed and compared with the conventional photoactivation method by experiments to determine their degree of conversion (DC). Absorbance measurements were performed using Fourier-transform infrared spectroscopy (FT-IR). A T-test was performed on DC results to compare the photoactivation techniques. We also used scanning electron microscopy (SEM) to analyze in-vitro the adhesion interface of the resin in human teeth. Results Our results showed that the use of the optimal dimming function, named as exponential, resulted in the significant reduction of the shrinkage stress (~36.88% ±6.56 when compared with the conventional method) without affecting the DC (t=0.86, p-value=0.44). The SEM analyses show that the proposed process can minimize or even eliminate adhesion failures between the tooth and the resin in dental restorations. Conclusion The results from this study can promote the improvement of the composite resin light curing process by the minimization of polymerization shrinkage effects, given an operational standardization of the photoactivation process.

Titanium alloys have excellent biocompatibility, and combined with their low elastic modulus, become more efficient when applied in orthopedic prostheses. Samples of Ti-15Mo-Zr and Ti-15Zr-Mo system alloys were prepared using an arc-melting furnace with argon atmosphere. The chemical quantitative analysis was performed using an optical emission spectrometer with inductively coupled plasma and thermal conductivity difference. The X-ray diffractograms, allied with optical microscopy, revealed the structure and microstructure of the samples. The mechanical analysis was evaluated by Vickers microhardness measurements. The structure and microstructure of alloys were sensitive to molybdenum and zirconium concentration, presenting α′, α″ and β phases. Molybdenum proved to have greater β-stabilizer action than zirconium. Microhardness was changed with addition of molybdenum and zirconium, having Ti-15Zr-10Mo (436 ± 2 HV) and Ti-15Mo-10Zr (378 ± 4 HV) the highest values in each system.

Dynamical Elastic Moduli of the Ti-13Nb-13Zr biomaterial alloy were obtained using the mechanical spectroscopy technique. The sample with heat treatment at 1170K for 30 minutes and water quenched with subsequent aging treatment at 670 K for 3 hours (TNZ + WQ + 670 K/3 h), was characterized through decay of free oscillations of the sample in the flexural vibration mode. The spectra of anelastic relaxation (internal friction and frequency) in the temperature range from 300 K to 625 K not revealed the presence of relaxation process. As shown in the literature, the hcp structure usually does not exhibit any relaxation due to the symmetry of the sites in the crystalline lattice, but if there is some relaxation, this only occurs in special cases such as low concentration of zirconium or saturation of the stoichiometric ratio of oxygen for zirconium. Dynamical elastic modulus obtained for TNZ + WQ + 670 K/3 h alloy was 87 GPa at room temperature, which is higher than the value for Ti-13Nb-13Zr alloy (64 GPa) of the literature. This increment may be related to the change of the proportion of α and β phases. Besides that, the presence of precipitates in the alloy after aging treatment hardens the material and reduces its ductility.

Titanium alloys are widely used in the manufacture of biomedical implants because they possess an excellent combination of physical properties and outstanding biocompatibility. Today, the most widely used alloy is Ti-6Al-4V, but some studies have reported adverse effects with the long-term presence of Al and V in the body, without mentioning that the elasticity modulus value of this alloy is far superior to the bone. Thus, there is a need to develop new Ti-based alloys without Al and V that have a lower modulus, greater biocompatibility, and similar mechanical strength. In this paper, we investigated the effect of Nb as a substitutional solute on the mechanical properties of Ti-Nb alloys, prepared in an arc-melting furnace and characterized by density, X-ray diffraction, optical microscopy, hardness and elasticity modulus measurements. The X-ray and microscopy measurements show a predominance of the α phase. The microhardness values showed a tendency to increase with the concentration of niobium in the alloy. Regarding the elasticity modulus, it was observed a nonlinear behavior with respect to the concentration of niobium. This behavior is associated with the presence of the α phase.

With the increase in life expectancy, biomaterials have become an increasingly important focus of research because they are used to replace parts and functions of the human body, thus contributing to improved quality of life. In the development of new biomaterials, the Ti-15Mo alloy is particularly significant. In this study, the Ti-15Mo alloy was produced using an arc-melting furnace and then characterized by density, X-ray diffraction, optical microscopy, hardness and dynamic elasticity modulus measurements, and cytotoxicity tests. The microstructure was obtained with β predominance. Microhardness, elasticity modulus, and cytotoxicity testing results showed that this material has great potential for use as biomaterial, mainly in orthopedic applications.

Mechanical spectroscopy measurements have been extensively used in the last decades to obtain information about many aspects of the behavior of solutes in metallic materials. Metals of body-centered cubic lattice that contain heavy interstitial elements (oxygen, nitrogen and carbon) in solid solution, present anelastic relaxation peaks when submitted to cyclic tensions, due to process know stress-induced ordering. Internal friction and frequency as a function of temperature were performed between 300 K and 650 K in a polycrystalline sample of Nb, for three distinct conditions, using a torsion pendulum inverted Kê-type operating in a frequency oscillation between 1Hz and 10 Hz range, with a heating rate of 1 K/min and pressure lower than 2 x 10-5 mbar. The experimental spectra obtained for each condition of the sample, were decomposed by the successive subtraction method in elementary Debye peaks. The following metal-interstitial interactions were identified: Nb-O and Nb-N for all conditions of the sample. From the anelastic relaxation parameters obtained (relaxation strength, peak temperature, activation energy and relaxation time) and lattice parameter (obtained from x ray diffraction), the determination of the oxygen and nitrogen interstitial diffusion coefficient in Nb was possible, for each condition of the sample.

Impurity interstitial atoms present in metals with BCC structure can diffuse in the metallic matrix by jumps to energetically equivalent crystallographic sites. Anelastic spectroscopy (internal friction) is based on the measurement of mechanical loss or internal friction as a function of temperature. Due to its selective and nondestructive nature, anelastic spectroscopy is well suited for the study of diffusion of interstitial elements in metals. Internal friction measurements were made using the torsion pendulum technique with oscillation frequency of a few Hz, temperature interval from 300 to 700 K, heating rate of about 1 K/min, and vacuum better than 10-5 mbar. The polycrystalline Nb and Ta samples used were supplied by Aldrich Inc. The results obtained showed thermally activated relaxation structures due to stress-induced ordering of oxygen atoms around the Nb (or Ta) atoms of the metallic matrix. The results were interpreted by three methods and led to activation enthalpy values for the diffusion of oxygen in Nb and Ta of 1.15 eV and 1.10 eV, respectively.

Measurements of internal friction as a function of temperature were performed in samples of Nb containing different amounts of substitutional (Zr) and interstitial (O, N) solutes. These data were resolved using the method of successive subtraction, into a series of constituent Debye peaks corresponding to different interactions. For each relaxation process we obtained the height (Q-1max) and temperature (Tp) of the peak, the activation energy (E) and the relaxation time (t0). The height, shape and temperature of the peaks depend on the concentration of interstitial and substitutional elements. With the addition of substitutional solute one can observed interactions between the two types of solutes (substitutional and interstitial), showing that the random distribution of the interstitial atoms was affected by presence of substitutional atoms. The peaks observed were associated with matrix-interstitial (Nb-O, Nb-N) and substitutional-interstitial (Zr-O) interaction processes.

Átomos de oxigênio, presentes em metais com estrutura cristalina cúbica de corpo centrado, são localizados preferencialmente em sítios octaedrais. Na ausência de uma tensão mecânica externa, estes átomos são distribuídos aleatoriamente. Na presença de oscilações mecânicas, a redistribuição dos átomos nos diferentes sítios deve ocorrer pela interação com esta tensão, levando a perdas na energia elástica. Este trabalho mostra o estudo da interação de átomos de oxigênio presentes em amostras da liga Nb-16% p. Ti, utilizando um pêndulo de torção. Os resultados mostram espectros bastante complexos, que foram decompostos em seus picos constituintes, representando os processos de relaxação devido à reorientação induzida por tensão de átomos e pares de átomos de oxigênio em torno de átomos de nióbio da matriz metálica e átomos de oxigênio em torno de átomos de titânio (interação substitucional-intersticial).

The Gorsky Effect was investigated by internal friction measurements in the Nb-46 wt.% Ti-H system. The internal friction measurements were performed in a torsion pendulum with frequency of 3.8 Hz in a temperature range from 80 to 700 K. An interpretation of the experimental data showed that the hydrogen diffusion coefficient D obeys the Arrhenius' law in the temperature interval of 300 to 700 K, with D0 = 7.4 × 10-4 cm²/s and activation energy E = (0.102 ± 0.005) eV. At low temperatures, Do and E were found to be respectively 2.0 × 10-4 cm²/s and (0.063 ± 0.005) eV, with a deviation of the Arrhenius law of higher temperatures.

In this study, MAO treatment was used to enrich, with bioactive Ca, Mg and P atoms, as-casted and heat-treated Ti-15Zr-xMo (x = 0, 5, 10 and 15 wt%) alloys, for potential use as advanced metallic biomaterials. The chemical composition of the surface was evaluated by EDS and XPS measurements. The morphology and microstructure was analyzed by OM and SEM images. Crystalline structure and phase composition were characterized by XRD measurements. The results indicated that the oxide layers were porous, with microstructural features of the bulk (grain size and secondary phases) slightly affecting the surface characteristics (pore size, chemical and phase composition). The crystalline structure of the oxide layers were composed by a mixture of anatase and rutile phases (TiO2), with a minority of tetragonal zirconia (ZrO2) and traces of CaCO3 and P2O3 compounds. Chemical analysis indicated that the oxide layers were composed mainly by Ti and Zr oxides, with successful incorporation of the bioactive elements. The obtained results evidenced that the surface characteristics of MAO-treated Ti surfaces can be properly adjusted by the addition of alloying elements and implementation of specific heat treatments on the substrate. This finding can be quite useful for the development of novel biomedical implants.

The present study produced binary titanium-niobium alloys Ti-xNb with high niobium percentage (x = 50, 80 e 90 wt.%) aiming to apply it as a base material in osseous implant devices. The produced TiNb alloys presented a cubic crystalline phase, lower corrosion rate than titanium, lower elastic modulus values, and superior cellular viability than titanium and niobium. The Ti50Nb alloy among all analyzed metallic substrates showed the best values of elastic modulus, corrosion properties, wettability, and cellular viability. Thus, this work suggests a Ti/Nb ratio close to 1 (Ti50Nb) displays optimum characteristics to apply in orthopedic devices.