Investigation of the Chemical Composition, Microstructure, Density, Microhardness, and Elastic Modulus of the New ß Ti-50Nb-xMo Alloys for Biomedical Applications.

ß-type titanium alloys with a body-centered cubic structure are highly useful in orthopedics due to their low elastic modulus, lower than other commonly used alloys such as stainless steel and Co-Cr alloys. The formation of the ß phase in titanium alloys is achieved through ß-stabilizing elements such as Nb, Mo, and Ta. To produce new ß alloys with a low modulus of elasticity, this work aimed to produce our alloy system for biomedical applications (Ti-50Nb-Mo). The alloys were produced by arc-melting and have the following compositions Ti-50Nb-xMo (x = 0, 3, 5, 7, and 12 wt% Mo). The alloys were characterized by density, X-ray diffraction, scanning electron microscopy, microhardness, and elastic modulus. It is worth highlighting that this new set of alloys of the Ti-50Nb-Mo system produced in this study is unprecedented; due to this, there needs to be a report in the literature on the production and structural characterization, hardness, and elastic modulus analyses. The microstructure of the alloys has an exclusively ß phase (with bcc crystalline structure). The results show that adding molybdenum considerably increased the microhardness and decreased the elastic modulus, with values around 80 GPa, below the metallic materials used commercially for this type of application. From the produced alloys, Ti-50Nb-12Mo is highlighted due to its lower elastic modulus.

A New α + ß Ti-15Nb Alloy with Low Elastic Modulus: Characterization and In Vitro Evaluation on Osteogenic Phenotype.

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 + ß type, with slow cooling promoting the formation of the α phase and rapid cooling the formation of the ß 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.

Surface Characterization of New ß Ti-25Ta-Zr-Nb Alloys Modified by Micro-Arc Oxidation.

The technique of surface modification using electrolytic oxidation, called micro-arc oxidation (MAO), has been used in altering the surface properties of titanium alloys for biomedical purposes, enhancing their characteristics as an implant (biocompatibility, corrosion, and wear resistance). The layer formed by the micro-arc oxidation process induces the formation of ceramic oxides, which can improve the corrosion resistance of titanium alloys from the elements in the substrate, enabling the incorporation of bioactive components such as calcium, phosphorus, and magnesium. This study aims to modify the surfaces of Ti-25Ta-10Zr-15Nb (TTZN1) and Ti-25Ta-20Zr-30Nb (TTZN2) alloys via micro-arc oxidation incorporating Ca, P, and Mg elements. The chemical composition results indicated that the MAO treatment was effective in incorporating the elements Ca (9.5 ± 0.4 %atm), P (5.7 ± 0.1 %atm), and Mg (1.1 ± 0.1 %atm), as well as the oxidized layer formed by micropores that increases the surface roughness (1160 nm for the MAO layer of TTZN1, 585 nm for the substrate of TTZN1, 1428 nm for the MAO layer of TTZN2, and 661 nm for the substrate of TTZN2). Regarding the phases formed, the films are amorphous, with low crystallinity (4 and 25% for TTZN2 and TTZN1, respectively). Small amounts of anatase, zirconia, and calcium carbonate were detected in the Ti-25Ta-10Zr-15Nb alloy.

Antimicrobial Cu-Doped TiO2 Coatings on the ß Ti-30Nb-5Mo Alloy by Micro-Arc Oxidation.

Among the different surface modification techniques, micro-arc oxidation (MAO) is explored for its ability to enhance the surface properties of Ti alloys by creating a controlled and durable oxide layer. The incorporation of Cu ions during the MAO process introduces additional functionalities to the surface, offering improved corrosion resistance and antimicrobial activity. In this study, the ß-metastable Ti-30Nb-5Mo alloy was oxidated through the MAO method to create a Cu-doped TiO2 coating. The quantity of Cu ions in the electrolyte was changed (1.5, 2.5, and 3.5 mMol) to develop coatings with different Cu concentrations. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron and atomic force microscopies, contact angle, and Vickers microhardness techniques were applied to characterize the deposited coatings. Cu incorporation increased the antimicrobial activity of the coatings, inhibiting the growth of Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa bacteria strains, and Candida albicans fungus by approximately 44%, 37%, 19%, and 41%, respectively. Meanwhile, the presence of Cu did not inhibit the growth of Escherichia coli. The hardness of all the deposited coatings was between 4 and 5 GPa. All the coatings were non-cytotoxic for adipose tissue-derived mesenchymal stem cells (AMSC), promoting approximately 90% of cell growth and not affecting the AMSC differentiation into the osteogenic lineage.

Preparation, structural, microstructural, mechanical and cytotoxic characterization of as-cast Ti-25Ta-Zr alloys.

Titanium alloys have been widely used as biomaterials, especially for orthopedic prostheses and dental implants, but these materials have Young's modulus almost three times greater than human cortical bones. Because of this, new alloys are being produced for the propose of decreasing Young's modulus to achieve a more balanced mechanical compatibility with the bone. In this paper, it is reported the development of Ti-25Ta alloys as a base material, in which was introduced zirconium, with concentration varying between 0 and 40 wt%, with the aim of biomedical applications. The alloys were prepared in an arc-melting furnace. The microstructural analysis was performed by x-ray diffraction as well as optical and scanning electron microscopy. Selected mechanical properties were analyzed by microhardness and Young's modulus measurements, and cytotoxicity analysis by indirect test. X-ray measurements revealed the presence of α″ phase in the alloy without zirconium; α″ + ß phases for alloys with 10, 20, and 30 wt% of zirconium, and ß phase only for the alloy with 40 wt% of zirconium. These results were corroborated by the microscopy results. The hardness of the alloy was higher than that of cp-Ti due to the actions of zirconium and tantalum as hardening agents. The Young's modulus decreases with high levels of zirconium due to the stabilization of the ß phase. The cytotoxicity test showed that the extracts of studied alloys are not cytotoxic for osteoblast cells in short periods of culture.

Preparation, structural, microstructural, mechanical, and cytotoxic characterization of Ti-15Nb alloy for biomedical applications.

Titanium alloys are widely used in the biomedical field due to their excellent resistance to corrosion, high mechanical strength/density ratio, low elastic modulus, and good biocompatibility. Niobium is a ß-stabilizer element that has the potential to decrease elastic modulus and possesses excellent corrosion resistance. In this article, Ti-15Nb alloy was prepared via arc-melting, with the aim of using it in biomedical applications to replace implants that fail due to mechanical incompatibility with human bone. This Ti-15Nb alloy was structurally, chemically, and microstructurally characterized. Its mechanical properties were analyzed via Vickers microhardness and elastic modulus measurements. The cytotoxicity of the alloy was evaluated via direct and indirect MTT tests. In the direct MTT test, the cells were grown on alloy and in the indirect test, Ti-15Nb alloy extracts were prepared (1 g/1 mL at 310 K for 48 hours). The results of chemical composition showed that the alloy produced has good quality and low content of gaseous impurities, such as oxygen and nitrogen. The obtained results for structure and microstructure indicated the presence of the martensite α' phase. The microhardness of the Ti-15Nb alloy is superior to that of cp-Ti due to solid solution hardening, and the alloy has a better elastic modulus as compared to pure titanium. Cytotoxic effects were not observed. The Ti-15Nb alloy shows good results of mechanical properties and does not show cytotoxic effects. In addition, morphological variations were not found in the cells and good cell adhesion in all the studied conditions was observed. In general, the alloy proposed in this article has satisfactory characteristics as a biomedical material.

Effect of Thermomechanical Treatments on the Phases, Microstructure, Microhardness and Young's Modulus of Ti-25Ta-Zr Alloys.

Titanium and its alloys currently are used as implants, possessing excellent mechanical properties (more suited than stainless steel and Co-Cr alloys), good corrosion resistance and good biocompatibility. The titanium alloy used for most biomedical applications is Ti-6Al-4V, however, studies showed that vanadium and aluminum cause allergic reactions in human tissues and neurological disorders. New titanium alloys without the presence of these elements are being studied. The objective of this study was to analyze the influence of thermomechanical treatments, such as hot-rolling, annealing and solution treatment in the structure, microstructure and mechanical properties of the Ti-25Ta-Zr ternary alloy system. The structural and microstructural analyses were performed using X-ray diffraction, as well as optical, scanning and transmission electron microscopy. The mechanical properties were analyzed using microhardness and Young's modulus measurements. The results showed that the structure of the materials and the mechanical properties are influenced by the different thermal treatments: rapid cooling treatments (hot-rolling and solubilization) induced the formation of α" and ß phases, while the treatments with slow cooling (annealing) induced the formation of martensite phases. Alloys in the hot-rolled and solubilized conditions have better mechanical properties results, such as low elastic modulus, due to retention of the ß phase in these alloys.

Effect of molybdenum on structure, microstructure and mechanical properties of biomedical Ti-20Zr-Mo alloys.

Titanium has an allotropic transformation around 883°C. Below this temperature, the crystalline structure is hexagonal close-packed (α phase), changing to body-centered cubic (ß phase). Zirconium has the same allotropic transformation around 862°C. Molybdenum has body-centered cubic structure, being a strong ß-stabilizer for the formation of titanium alloys. In this paper, the effect of substitutional molybdenum was analyzed on the structure, microstructure and selected mechanical properties of Ti-20Zr-Mo (wt%) alloys to be used in biomedical applications. The samples were prepared by arc-melting and characterized by x-ray diffraction with subsequent refinement by the Rietveld method, optical and scanning electron microscopy. The mechanical properties were analyzed by Vickers microhardness and dynamic elasticity modulus. X-ray measurements and Rietveld analysis revealed the presence of α' phase without molybdenum, α'+α″ phases with 2.5wt% of molybdenum, α″+ß phases with 5 and 7.5wt% of molybdenum, and only ß phase with 10wt% of molybdenum. These results were corroborated by microscopy results, with a microstructure composed of grains of ß phase and lamellae and needles of α' and α″ phase in intra-grain the region. The hardness of the alloy was higher than the commercially pure titanium, due to the action of zirconium and molybdenum as hardening agents. The samples have a smaller elasticity modulus than the commercially pure titanium.