Titanium-based Alloys Research Articles

Development of a biocompatible Ti-Nb alloy for orthopaedic applications

Metallic biomedical implants such as titanium-based alloys are very useful for orthopaedic applications due to their excellent properties which responds to changes in temperature and other conditions. However, biological toxicity due to alloying elements and relatively high Young’s modulus or mechanical incompatibilities of previously used Ti alloys have necessitated the development of biocompatible alloys with compatible mechanical properties such as beta-titanium alloys. This study aims at production of beta-titanium alloy with enhanced properties by varying milling speeds. Ti and Nb powders were mechanically alloyed using the high energy ball-mill Zoz-Simoloyer® to produce Ti-7Nb alloys by varying the milling speed. The milling process produced irregular shaped powders with increasing particles sizes as the milling speed increased due to fragmentation and cold welding during agglomeration. The mechanical alloying process had good yield. The predominant phases of the inhomogeneously milled alloy were alpha and beta phases.

Новые перспективные сплавы на основе титана

Новые перспективные сплавы на основе титана

Quasi-Homogenous Model of Electrochemical Machining of Turbine Engine Parts

Abstract In order to increase the efficiency of jet engines hard to machine nickel-based and titanium-based alloys are in common use for aero engine components such as blades and blade integrated disks (BLISK). Electrochemical Machining (ECM) provides an economical and effective method for machining high strength and heat-resistant materials into complex shapes with high material removal rate without tool wear and without inducing residual stress. This article presents the physical and mathematical models of electrochemical shaping used in the manufacture of turbine engine parts. The modelling is based on the assumption that the multi-phase mixture filling the gap is treated as two-phase quasi-homogenous medium. The model describes the workpiece shape evolution in time, distribution the local gap size, flow parameters such as the static pressure and the velocity, temperature and void fraction as result of gas generation. The major features of the numerical computer program are briefly described with a selected example of machining a typical turbine blade. The results of computer simulation of effects of setting parameters ECM on accuracy-machined profile are discussed. The improvement of accuracy has been reached by using described sequence of ECM and Pulse ECM processes.

Formation and Properties of Biomedical Ti-Ta Foams Prepared from Nanoprecursors by Thermal Dealloying Process.

The paper presents a promising method of preparation of titanium-based foams by the thermal dealloying method. The first step of this study was the Ti-Ta-Mg based nanopowder preparation using the mechanical alloying (MA) process performed at room temperature. The next step was forming the green compacts by cold pressing and then sintering with magnesium dealloying from the titanium-based alloy structure. The mechanism of the porous structure formation was based on the removal of magnesium from the titanium alloy at a temperature higher than the boiling point of magnesium (1090 °C). The influence of the Mg content on the formation of the porous Ti-30Ta foam has been investigated. The sintering stage was performed in vacuum. During the dealloying process, the magnesium atoms diffuse from the middle to the surface of the sample and combine to form vapors and then evaporate leaving pores surrounded by the metallic scaffold. The porosity, the mechanical properties as well as biocompatibility have been investigated. The titanium-based foam of high porosity (up to 76%) and the pore size distribution from nano- to micro-scale have been successfully prepared. For the medical applications, the Ti-Ta metallic foams have shown a positive behavior in the MTT test. The as-shown results clearly exhibit a great potential for thermal dealloying in the preparation of porous structures.

Effect of Al alloying on cavitation erosion behavior of TaSi2 nanocrystalline coatings.

To broaden the scope of non-aerospace applications for titanium-based alloys, both hexagonal C40 binary TaSi2 and ternary Al alloyed TaSi2 nanocrystalline coatings were exploited to enhance the cavitation erosion resistance of Ti-6Al-4V alloy in acidic environments. To begin with, the roles of Al addition in influencing the structural stability and mechanical properties of hexagonal C40 Ta(Si1-xAlx)2 compounds were modelled using first-principles calculations. The calculated key parameters, such as Pugh's index (B/G ratio), Poisson's ratio, and Cauchy pressures, indicated that there was a threshold value for Al addition, below which the increase of Al content would render the Ta(Si1-xAlx)2 compounds more ductile, but above which no obvious change would occur. Subsequently, the TaSi2 and Ta(Si0.875Al0.125)2 coatings were prepared and their microstructure and phase composition were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Both the two coatings exhibited a uniform thickness of 15 μm and a densely packed structure mainly composed of spherically shaped nanocrystallites with an average diameter of about 5 nm. Nanoindentation measurements revealed that Al alloying reduced the hardness (H) and elastic modulus (E) values of the TaSi2 coating. Ultrasonic cavitation erosion tests were carried out by immersing coated and uncoated samples in a 0.5 M HCl solution. The cavitation-erosion analysis of the tested samples was investigated by various electrochemical techniques, mass loss weight and SEM observation. The results suggested that both coated samples provided a better protection for Ti-6Al-4V against the cavitation-erosion damage in acidic environments, but the addition of Al further improved the cavitation-erosion resistance of the TaSi2 coating.

Microstructure features of Ni-based and Ti-based alloys formed by method of wire-feed electron beam additive technology

In the present study, a microstructural investigation of wire-feed EBAM-manufactured nickel-based and titanium-based alloys were conducted by producing single wall sample with 16 and 19 vertical layers, respectively. It was shown that in obtained material microstructural and elemental gradient presents. The results of the research show that dendrites and grains grow epitaxial in the direction of temperature gradient. Non-directional dissipation of heat on the edge of the sample leads to formation of equiaxed structure. Chosen parameters allow to produce low-defective samples by EBAM technology.

Standardization of proton induced X-ray emission for analysis of trace elements in thick samples

This paper presents the standardization of proton induced X-ray emission (PIXE) technique for the analysis of trace elements in thick, standard samples. Three standard reference materials, titanium, copper, and iron base alloys, were used for the study due to their availability. The proton beam was accelerated up to 2.57 MeV energy by 5UDH-II tandem Pelletron accelerator, and samples were irradiated at different geometries and durations. Spectra were acquired using a multi-channel spectrum analyzer, and spectra analyses were done using GUPIXWIN software for determination of elemental concentrations of trace elements. The obtained experimental data were compared with theoretical data and results were found to be in close agreement.

Homogeneous Modelling and Analysis of Hip Prosthesis Using FEA

With keen interest in hip prosthesis, optimization of orthopaedic implant is carried out in this work to limit probability of implant failure and increase success rate of surgery. The focal point of work is to calculate stress at the interface between implant and bone. Reduction of stress level in the femur implant because of major load carried by prosthesis because of its higher stiffness cause aseptic loosening of the implant which is a consequence of bone resorption phenomenon. The problem of bone resorption can be resolved by using porous titanium-based alloy with low young’s modulus but these materials cannot sustain desirable mechanical properties because of high porosity. In proposed work finite element analysis of hip prosthesis by using three different titanium-based alloys with varying young’s modulus (Homogeneous Material) has been carried out to identify material with optimum balance of porosity and stress shielding. On doing comparisons of results among three different models, model with intermediate value of young’s modulus was realised to deliver the best result.

Investigation of cast and annealed Ti25Nb10Zr alloy as material for orthopedic devices

In the present work, we report the preparation of a novel titanium-based alloy, namely Ti25Nb10Zr, by cold crucible levitation melting technique. The cast alloy consists of a complex microstructure with large Beta phase grains (54%, ˜50–150 µm) with a regularly connected net of Alpha′ (orthorhombic, 46%) phase running along boundaries and across the grains and keeping a regular misorientation with respect to the Beta phase. An intermeshed 51% Alpha and 49% Beta phases with lamellar microstructure were found by annealing. The electrochemical tests showed that both alloys were affected by the corrosion process. A good corrosion resistance in SBF at 37 °C was found for the cast form. The cast alloy is more resistant when immersed into solutions with pH2 and pH7, while the annealed one is resistant in pH5 solution. Surface potential of both alloys is negative, with the annealing process leading to a slight decrease of that property. Collectively, the biological results indicate a more favorable viability on cast form as compared to annealed one, suggesting that the cast alloy is promising for biomedical applications.

MICROSTRUCTURAL AND MECHANICAL ASPECTS OF FRICTION WELDED DISSIMILAR JOINTS FOR AERO ENGINE APPLICATION

Gas turbine engines demand material with unique properties like high-temperature oxidation and corrosion resistance, high specific strength, etc. All over the world material development to meet these requirements has led to the development of novel alloys. While Titanium base alloys are used in the low-temperature regime of the gas turbine engine, Nickel-basedsuperalloys are used for hot end components of the engine. With the increase in the temperature requirement for the turbine parts, the form of the Ni-based superalloys changed from wrought to cast superalloys. As an inherent process of investment cast superalloy blades and vanes which has serpentine passages for air cooling, these passages are required to be closed after casting. The numerous adapters also need to be joined on the cast superalloy casings for various instrumentation, lube oil ports. These cast superalloys are nonweldable and joining these pose a challenge. In this present investigation, the joining of the Nibasedsuperalloy BZL12Y and martensitic stainless steel AE961W using rotary friction welding process. The mechanical properties of the dissimilar joints were evaluated as per the ASTM standards. Microstructural features of various regions of welded joints using optical microscopy (OM) and scanning electron microscopy (SEM). The material is welded in different condition to obtain the maximum tensile strength of the weld joint. From this investigation, it was found that the combination of aging and h & t condition weld joint gives good strength and a stable hardness value. Correlation between tensile properties and microstructural features were analyzed and reported in this paper.

Superplasticity of Ti-6Al-4V Titanium Alloy: Microstructure Evolution and Constitutive Modelling.

Determining a desirable strain rate-temperature range for superplasticity and elongation-to-failure are critical concerns during the prediction of superplastic forming processes in α + β titanium-based alloys. This paper studies the superplastic deformation behaviour and related microstructural evolution of conventionally processed sheets of Ti-6Al-4V alloy in a strain rate range of 10–5–10–2 s–1 and a temperature range of 750–900 °C. Thermo-Calc calculation and microstructural analysis of the as-annealed samples were done in order to determine the α/β ratio and the grain size of the phases prior to the superplastic deformation. The strain rate ranges, which corresponds to the superplastic behaviour with strain rate sensitivity index m ˃ 0.3, are identified by step-by-step decreasing strain rate tests for various temperatures. Results of the uniaxial isothermal tensile tests at a constant strain rate range of 3 × 10−4–3 × 10−3 s−1 and a temperature range of 800–900 °C are presented and discussed. The experimental stress-strain data are utilized to construct constitutive models, with the purpose of predicting the flow stress behaviour of this alloy. The cross-validation approach is used to examine the predictability of the constructed models. The models exhibit excellent approximation and predictability of the flow behaviour of the studied alloy. Strain-induced changes in the grain structure are investigated by scanning electron microscopy and electron backscattered diffraction. Particular attention is paid to the comparison between the deformation behaviour and the microstructural evolution at 825 °C and 875 °C. Maximum elongation-to-failure of 635% and low residual cavitation were observed after a strain of 1.8 at 1 × 10−3 s−1 and 825 °C. This temperature provides 23 ± 4% β phase and a highly stable grain structure of both phases. The optimum deformation temperature obtained for the studied alloy is 825 °C, which is considered a comparatively low deformation temperature for the studied Ti-6Al-4V alloy.

Property optimization of Zr-Ti-X (X = Ag, Al) metallic glass via combinatorial development aimed at prospective biomedical application

Exceptional materials with enhanced bio-compatibility are a quest among the researchers in the medical community. Conventional crystalline materials, including 316L stainless steel, titanium and titanium-based alloys, are most commonly used for medical equipment or devices. However, materials with greater compatibility with biological systems should be studied. An amorphous solid, such as Zirconium (Zr)-based metallic glass, is a possible alternative to the conventional crystalline materials. The prospect of achieving multi-property requirements (i.e., high corrosion and wear resistance, lower elastic modulus and enhanced antibacterial capacity) with Zr-based thin film metallic glass (TFMG) were studied in this work. To form a ternary system with the optimized composition of Zr46Ti40Ag14 and Zr46Ti43Al11, TFMGs were fabricated by magnetron co-sputtering or combinatorial development of a binary Zr-Ti alloy with silver (Ag) or aluminum (Al). The structural characterization via grazing incidence x-ray diffraction (GI-XRD) and high-resolution transmission electron microscopy (HR-TEM) manifested an amorphous structure for the ternary TFMGs. The electrochemical analyses of the ternary systems revealed lower corrosion- and passive-current density when compared to 316L stainless steel and commercially pure titanium (cp-Ti). These data demonstrated that TFMGs have better corrosion resistant characteristics. Moreover, the systems exhibited appreciable hardness and elastic modulus lower than 316L stainless steel and cp-Ti. Both of the ternary TFMGs exhibited hydrophobicity, whereas only the Zr46Ti40Ag14 exhibited significant antibacterial properties and reduced the growth of methicillin-resistant Staphylococcus aureus. The combination of such desirable properties makes these TFMGs an excellent candidate material for a wide range of biomedical applications.

Structural, elastic, magnetic and electronic properties of TiX2(X = Cr, Mn) alloys

The structural, elastic, magnetic and electronic properties of titanium-based alloys TiX2(X = Cr, Mn) are investigated by the first-principles calculations based on density functional theory using the Vienna ab-initio simulation code. The lattice constants of TiX2(X = Cr, Mn) alloys are optimized for various possible structures such as hexagonal, tetragonal and orthorhombic. TiX2(X = Cr, Mn) alloys are highly stable in hexagonal structure with the space group P63/mmc at ambient pressure. A pressure-induced structural phase transition from hexagonal structure to the tetragonal structure is observed in TiCr2at 443.3 GPa and in TiMn2hexagonal structure to orthorhombic structure is at 295.05 GPa. The electronic structure shows that TiX2(X = Cr, Mn) alloys are metallic in nature at all pressures. The magnetic property of nonmagnetic TiX2(X = Cr, Mn) alloys are analyzed by doping with ferromagnetic materials (Fe, Co and Ni) using the stoichiometries of TiX[Formula: see text]Y[Formula: see text] (X = Cr, Mn; Y = Fe, Co and Ni; z = 0.5,1,1.5). It is seen that the magnetic moment is induced by the substitution of ferromagnetic materials with TiX2alloys.

Treating Titanium Particle-Induced Inflammation with Genetically Modified NF-κB Sensing IL-4 Secreting or Preconditioned Mesenchymal Stem Cells in Vitro.

Titanium and titanium-based alloys are widely used in orthopaedic implants. Total joint replacement is very successful; however, the foreign body response and chronic inflammation caused by implant-derived biomaterial debris still remain as unsolved issues. Aseptic loosening accompanied by wear debris-induced osteolysis (bone loss) is one of the most frequent causes for late failure and revision surgery. Mesenchymal stem cells (MSCs) and IL-4 may be possible treatment strategies because of their immunomodulatory properties. We investigated the efficacy of novel MSC-based treatments on immunomodulation and osteogenic differentiation in an innovative cell coculture model of titanium particle-induced inflammation in the periprosthetic tissues. MSCs and macrophages were collected from the bone marrow of Balb/c mice. Both MSCs and macrophages (representing endogenous cells at the periprosthetic tissue) were seeded on the bottom wells of the 24-well transwell plates. We generated genetically modified NF-κB sensing IL-4 secreting MSCs (inflammatory responsive MSCs) and MSCs preconditioned by lipopolysaccharide and TNF-α to further enhance their immunomodulatory function. These modified MSCs (representing exogenous therapeutic cells implanted to the periprosthetic tissue) were seeded on the upper chambers of the transwell plates. These cocultures were then exposed to titanium particles for 7 days. NF-κB sensing IL-4 secreting MSCs showed strong immunomodulation (significantly reduced TNF-α and induced Arg1 expression) and promoted early osteogenesis (significantly induced Runx2, ALP, and β-catenin as well as reduced Smurf2 expression) at day 7. IL-4 secreting MSCs also decreased TNF-α protein secretion as early as day 3 and increased IL-1ra protein secretion at day 7, suggesting efficacious immunomodulation of particle-induced inflammation. Preconditioned MSCs did not show significant immunomodulation in this short-term experiment, but ALP and β-catenin expression were significantly induced at day 7. Our results suggest that genetically modified IL-4 secreting MSCs and preconditioned MSCs have the potential to optimize bone regeneration in inflammatory conditions including periprosthetic osteolysis.

The Influence of Microstructure on the Passive Layer Chemistry and Corrosion Resistance for Some Titanium-Based Alloys.

The effect of microstructure and chemistry on the kinetics of passive layer growth and passivity breakdown of some Ti-based alloys, namely Ti-6Al-4V, Ti-6Al-7Nb and TC21 alloys, was studied. The rate of pitting corrosion was evaluated using cyclic polarization measurements. Chronoamperometry was applied to assess the passive layer growth kinetics and breakdown. Microstructure influence on the uniform corrosion rate of these alloys was also investigated employing dynamic electrochemical impedance spectroscopy (DEIS). Corrosion studies were performed in 0.9% NaCl solution at 37 °C, and the obtained results were compared with ultrapure Ti (99.99%). The different phases of the microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Chemical composition and chemistry of the corroded surfaces were studied using X-ray photoelectron spectroscopy (XPS) analysis. For all studied alloys, the microstructure consisted of α matrix, which was strengthened by β phase. The highest and the lowest values of the β phase’s volume fraction were recorded for TC21 and Ti-Al-Nb alloys, respectively. The susceptibility of the investigated alloys toward pitting corrosion was enhanced following the sequence: Ti-6Al-7Nb < Ti-6Al-4V << TC21. Ti-6Al-7Nb alloy recorded the lowest pitting corrosion resistance (Rpit) among studied alloys, approaching that of pure Ti. The obvious changes in the microstructure of these alloys, together with XPS findings, were adopted to interpret the pronounced variation in the corrosion behavior of these materials.

Determinación experimental del equilibrio de fases en el sistema Ti- Nb-Mn a temperaturas entre 1150°C y 1200°C

El aumento y envejecimiento de la población mundial conlleva un progresivo uso de implantes biomédicos. Las aleaciones base titanio, han sido aplicadas extensamente. Aleaciones Ti-Mn, Ti-Nb, Ti-Nb-Mn y Ti-Ta-Nb-Mn se han postulado con un potencial uso biomédico para las siguientes generaciones. Información disponible del sistema en equilibrio Ti-Nb-Mn es escasa en la literatura. El presente trabajo contribuye en el estudio experimental de las isotermas 1150°C y 1200°C del diagrama ternario Ti-Nb-Mn, establecidas mediante técnicas de microscopia electrónica de barrido, espectroscopia por dispersión de energía y comparados con secciones isotérmicas simuladas mediante Thermo-Calc®. Se encuentran diferencias entre simulaciones ternarias y binarias. Los experimentos muestran la aparición de bTiMn a diferencia de lo reportado y simulado. Se presentan zonas obtenidas experimentalmente cercanas a composiciones líquidas de los diagramas ternarios a 1150°C y 1200°C. A 1150°C se presenta coexistencia de bTiMn y TiMn2. A 1200°C existe coexistencia de fases líquida, bTiMn y TiMn2.

Additive Manufacturing of Titanium and Titanium-based Alloys

Additive Manufacturing of Titanium and Titanium-based Alloys

In vitro biocompatibility of novel titanium-based amorphous alloy thin film in human osteoblast-like cells

In vitro biocompatibility of novel titanium-based amorphous alloy thin film in human osteoblast-like cells

Effects of reinforced nanoparticles with surfactant on surface quality and chip formation morphology in MQL-turning of superalloys

Superalloys (nickel and titanium-based alloys) are grouped as difficult-to-cut materials. Therefore, due to poor machinability of superalloys, their machining is a great challenge for manufacturing sectors. Surface quality of work part and chip formation morphology are considered as the main machinability attributes in machining superalloys. Although numerous studies have been focused on this context, however, no work was found on the effect of nanoparticles stability on nanofluid performance and consequently on machinability attributes, in principle surface quality and chip formation morphology. In the present study, the importance of nanoparticles stability by adding of surface active agent (surfactant) as additive elements was evaluated. Two kinds of nanoparticles including nano copper-oxide and nano silicon-oxide with different volume fraction were used to prepare nanofluid solution. In addition, surfactant from the group of Sodium Dodecyl Sulfate (SDS) which is appropriate for polar fluid was selected. Scanning Electron Microscope (SEM) images were utilized to analyse the machined surface of the work part. Cutting fluids were prepared in three conditions, including nanofluid with surfactant (reinforced nanofluid), nanofluid without surfactant, and conventional cutting fluid (without nanoparticles). The average surface roughness Ra was considered as the surface quality attribute. The recorded values of Ra and chip formation morphology indicated that reinforced nanofluid could significantly improve the cutting mechanism as compared with nanofluid without surfactant and conventional fluid. The main reason for this phenomenon can be attributed to high ability of surfactant to disperse nanoparticles in the fluid medium as well as high capability to prevent nanoparticles aggregation. After a short period, the nanoparticles in nanofluid without surfactant attached to other particles and a massive mass (nanoparticles aggregation) was formed which led to quick settling of nanoparticles. By settling of nanoparticles, the environment becomes free of nanoparticles and similar properties and capability as conventional fluid may occur.

Turning Titanium Alloy, Grade 5 ELI, With the Implementation of High Pressure Coolant.

In the machining of difficult-to-cut alloys, such as titanium-based alloys, the delivery of a cutting fluid with high pressure can increase machining efficiency and improve process stability through more efficient chip breaking and removing. Proper selection of machining conditions can increase the productivity of the process while minimizing production costs. To present the influence of cutting fluid pressure and chip breaker geometry on the chip breaking process for various chip cross-sections Grade 5 ELI titanium alloy turning tests were carried out using carbide tools, H13A grade, with a -SF chip breaker geometry under the cutting fluid pressure of 70 bar. Measurements of the total cutting force components for different cutting speeds, feeds, and cutting depth in finishing turning were carried out. The analysis of the obtained chips forms and the application area of the chip breaker have been presented. It was proved that for small depth of cut (leading to small chip cross-section) the cutting fluid pressure is the main cause of the chip breakage, since the insert chip breaker does not work. On the other hand, for bigger depths of cut where the chip breaker goes in action, the cutting fluid pressure only supports this process. For medium values of depths of cut the strength of chip is high enough so that the pressure of the cutting fluid cannot cause chip breaking. A chip groove is not filled completely so the chip breaker cannot play its role.