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The main goal of this study was to achieve poreless titanium alloys with nanocrystalline structure. To this end, the influence of Ta, Mg and Zn content on the properties of Ti alloys was investigated. At first, nanocrystalline powders of TixTayMg and TixTayZn, where x = (30 and 40 wt.%) and y = (3 and 5 wt.%), were prepared using the mechanical alloying process at room temperature. Then, hot-pressing at 750 °C under vacuum was applied for 10 s to consolidate powders. The structure, microstructure, chemical composition, mechanical properties, corrosion resistance, wettability and MTT assay have been investigated. Alloys with Mg were allowed to undergo a shorter mechanical alloying process, achieve greater grain refinement after consolidation and improve mechanical properties. In all cases with increasing amounts of additives in titanium, more Ti-β phase was available. Furthermore, with increasing elements content, hot-pressed alloys consisting of Mg tended to have a more hydrophobic surface. According to the MTT test, all new alloys show non-toxic properties. Among all alloys tested in this study, Ti40Ta5Mg had the most interesting properties for biomedical applications, the highest content of Ti-β phase (81.3%), lowest porosity (0.07%), lowest Young modulus (102.1 GPa) and the lowest surface free energy (38.45 mN/m). [ABSTRACT FROM AUTHOR]

With the continuously rapid development of materials science, better properties are equably required in the area of material surface engineering, especially the surface friction and high-temperature oxidation resistance of titanium alloy. It is a great approach to select a scientific way for surface treatment to improve the surface performance so as to obtain surface films/coatings/layers. It can provide a vital latent remedy to the insufficient high-temperature oxidation resistance and wear resistance of titanium alloys. Pack cementation is a reliable means at present by virtue of its distinct composition, covering pollution-free and the firm metallurgical bonding between the alloying coating and the matrix. In the last few years, with the growing demands for the surface performance of materials in multifarious harsh environments, the coating obtained by pack cementation is developing toward controlling coating composition accurately and applying it to complex parts. This review opens with an abbreviated introduction of pack cementation technology. The recent developments of pack cementation technology for enhancing diverse surface properties are scientifically reviewed in the aspects of background, previous research results and the future development directions. [ABSTRACT FROM AUTHOR]

The aircraft industry is always looking for improved efficiency through higher in-service engine temperatures and lighter structures. Titanium-based alloys are good candidates for such applications because of their high specific strength. However, when exposed to high-temperature oxidizing environments, a large amount of dissolved oxygen can be found in such alloys beneath the growing oxide scale, possibly leading to embrittlement. Consequently, evaluating the oxidation resistance of these alloys is essential. With this aim, long-term oxidation tests were carried out on Ti6242S alloy between 500 and 650 °C to study the effect of temperature, surface preparation and microstructure on oxide scale and oxygen dissolution. While increasing the temperature from 560 to 625 °C led to accelerated oxidation kinetics, surface preparation had no noticeable effect on mass variations and oxygen diffusion profiles. Regarding microstructure, when comparing Ti6242S samples having similar α-phase fraction but very different microstructures (fineness and morphology), there wasn't any significant effect found on mass change and oxygen diffusion after 1 kh at 650 °C. [ABSTRACT FROM AUTHOR]

Amorphous metallic glass has excellent mechanical, physical, chemical and mechanical properties, and is an important development direction and research hotspot of metal composite reinforcements. As a stable, simple, efficient and scalable technology, mechanical alloying provides an effective way to prepare amorphous metal glass. In this work, titanium-based amorphous metallic glass was used to the research object, and the mechanical alloying method was used to achieve efficient and controllable preparation of amorphous powders. The micro-morphology of sample surface was analyzed with the help of scanning electron microscope, amorphous phase structures were characterized by X-ray diffraction, and mechanical properties were measured by micro hardness tester. The results show that the prepared metal powders were relatively uniform and had good amorphous structure characteristics. The hardness test shows that as prepared amorphous metal powder hadan improved hardness of 6 615 Mpa, which could be used as an important part in reinforcing materials. [ABSTRACT FROM AUTHOR]

This work is devoted to the finite-element modeling of the deformation mode of a small-diameter rod billet during pressure hot treatment in the combination of radial shear rolling (RSR) and rotary forging (RF). Modeling is performed using a rheological model of the Ti–6Al–4V titanium alloy using the QForm VX program. The combination of RSR for one passage of a billet 15 mm in diameter to a rod 12 mm in diameter and subsequent RF in 1, 2, and 3 passages with the formation of rods 11, 10, and 8 mm in diameter is modeled. The operation-by-operation accumulation of the plastic deformation in nonuniformity conditions of its distribution is taken into account. Intermediate and final plastic deformation fields, deformation rates, and average stresses are found. It is shown that the distribution of the plastic deformation after RSR has the pronounced gradient character with a minimal value (3 and larger) at the cross-section periphery and a minimal value (about 1) in the center. Due to this, RF, even with small reductions, leads to a substantial increase in uniformity of the deformation mode when compared with the billet after the same diameter after radial shear rolling only. In addition, residual tensile stresses decrease due to compressing stresses during RF. The direct experimental approval of the combined deformation method is performed for the promising Ti–Zr–Nb shape memory alloy of medical prescription when fabricating rods 7–8 mm in diameter under pilot production conditions. The results of modeling are qualitatively confirmed by the metallographic analysis. The prospects of a combination of RSR and RF for the development of industrial fabrication technologies of small-diameter rods with a high uniformity of finely dispersed structure are shown. [ABSTRACT FROM AUTHOR]

At high temperatures under oxidizing environments, titanium-based alloys form an oxide scale and dissolve large amount of oxygen in their metallic matrix. Oxygen dissolution is a cause of embrittlement. Nitrogen is a secondary oxidant, which also dissolves in titanium during oxidation in air. Oxidation experiments of Ti-6Al-2Sn-4Zr-2Mo-0.1Si titanium-based alloy at 650 °C for 1000 h in synthetic air (20%O2- 80%N2) and in a mixture of 20%O2-80%Ar, showed that nitrogen reduces both oxide scale growth and oxygen dissolution. Atom probe tomography revealed that nitrogen effect is due to the formation of an interfacial layer of nitride Ti2N but also to the formation of a nitrogen rich a-Ti-based solid solution, which both act as difiusion barriers for oxygen because of their low oxygen solubility.

A comparative study of the antifriction characteristics of specimens of the VT6 titanium-based alloy subjected to nitriding without preliminary treatment and after hydrogen heat treatment has been carried out. Hydrogen heat treatment that precedes nitriding reduces the coefficient of friction of the nitrided specimens of the VT6 alloy in pair with the 12Kh18N10T stainless steel by 4-9% under dry friction and increases it by ~47% in a working fluid, which is a 0.9% NaCl solution. Hydrogen heat treatment combined with ionplasma nitriding reduces the coefficient of friction in working fluid by ~41%. [ABSTRACT FROM AUTHOR]

Nowadays, one of the main challenges in metal implants for bone substitution is the achievement of an elastic modulus close to that of human cortical bone as well as to provide an adequate interaction with the surrounding tissue avoiding in vivo foreign body reaction. From this perspective, a new Ti-based alloy has been developed with Nb and Hf as alloying elements which are known as non-toxic and with good corrosion properties. The microstructure, mechanical behaviour and the physicochemical properties of this novel titanium alloy have been studied. Relationship of surface chemistry and surface electric charge with protein adsorption and cell adhesion has been evaluated due to its role for understanding the mechanism of biological interactions with tissues. The Ti25Nb21Hf alloy presented a lower elastic modulus than commercial alloys with a superior ultimate strength and yield strength than CP-Ti and very close to Ti6Al4V. It also exhibited good corrosion resistance. Furthermore, the results revealed that it had no cytotoxic effect on rat mesenchymal stem cells and allowed protein adsorption and cell adhesion. The experimental results make this alloy a promising material for bone substitution or for biomedical devices. [ABSTRACT FROM AUTHOR]

Phase equilibria in the Fe–Sn–Ti ternary system at 1073 and 1273 K were experimentally investigated through alloy sampling approach facilitated with electron probe micro-analyzer and X-ray diffraction. Two ternary compounds TiFe 2 Sn and Ti 2 FeSn were detected. Ten 3-phase equilibria at 1073 K, including β(Ti)+Ti 3 Sn+FeTi, Ti 3 Sn+FeTi+Ti 5 Sn 3 , FeTi+Ti 5 Sn 3 +Ti 2 FeSn, Ti 2 FeSn+Fe 2 Ti+TiFe 2 Sn, Ti 2 FeSn+Ti 5 Sn 3 +Ti 6 Sn 5 , FeTi+Fe 2 Ti+Ti 2 FeSn, Ti 2 FeSn+Ti 6 Sn 5 +TiFe 2 Sn, TiFe 2 Sn+Ti 6 Sn 5 +Liquid, TiFe 2 Sn+Fe 5 Sn 3 +Liquid and α(Fe)+Fe 2 Ti+TiFe 2 Sn, and seven 3-phase equilibria including β(Ti)+Ti 3 Sn+FeTi, Ti 3 Sn+FeTi+Ti 5 Sn 3 , Ti 3 Sn+Ti 2 Sn+Ti 5 Sn 3 , FeTi+Fe 2 Ti+Ti 5 Sn 3 , Fe 2 Ti+Ti 2 FeSn+Ti 5 Sn 3 , Ti 2 FeSn+Fe 2 Ti+TiFe 2 Sn and Ti 2 FeSn+Ti 6 Sn 5 +TiFe 2 Sn at 1273 K were experimentally confirmed. At 1073 K, the homogeneity ranges of Ti 2 FeSn were 45.5–51.4 at% Ti and 24–27.7 at.% Sn while TiFe 2 Sn exhibited a large homogeneity range of 46.9–66.4 at% Fe and 22.7–26.4 at% Sn, the solubility of Sn in Fe 2 Ti,Fe in Ti 5 Sn 3 , Ti in Fe 5 Sn 3 and Fe in Ti 6 Sn 5 can be up to 4.6 at.%, 10.2 at%, 3.7 at% and 21 at%, respectively, while at 1273 K, Solubility of Sn in Fe 2 Ti considerably increased to 10.8 at%, Fe in Ti 5 Sn 3 changes little. According to the measured phase relations, an invariant reaction was further deduced, which was Fe 2 Ti+Ti 5 Sn 3 ↔FeTi+Ti 2 FeSn occurring between 1073 K and 1123 K. [ABSTRACT FROM AUTHOR]

Abstract: In order to increase the efficiency of jet engines hard to machine titanium- and nickel-based alloys are in common use for blade and disk materials. With Electrochemical Machining (ECM) highest material removal rates can be achieved at best surface qualities. However for tool design, knowledge of local material dissolution is indispensable. This paper deals with basic research on the electrochemical machinability of selected modern titanium- and nickel-based alloys for aero engine components. Therefor experimental results of feed rate as a function of current density for an ECM sinking operation with a cylindrical tool electrode and external flushing are compared to the theoretical dissolution behavior according to Faraday's law. Furthermore surface properties were examined in terms of SEM and EDX analysis of the rim zone. [Copyright &y& Elsevier]

The orientation relationships between austenite and α′ and α″ martensite lattices in titanium and zirconium alloys is performed in view of the possibility of the formation of self-accommodating complexes, which is an important component of the shape memory effect. Different diffraction patterns calculated for various matrices of the orientation relationship were compared with the experimental patterns for TiZrNb alloy using a formula developed for the optimal expression of the orientation relationship for α″. The generalization and analysis of the literature data for titanium- and zirconium-based solid solutions performed using the developed algorithm lead us to conclusions regarding the tendency of α′ martensite in titanium-based solid solutions to self-accommodate, which occurred more strongly than that in zirconium-based alloys, and the best results in shape memory realization should be expected in Ti-Ta and Ti-Nb systems. Possible reasons for the absence of the shape memory effect for α′ martensite in titanium- and zirconium-based alloys, with regard to the necessary crystallographic conditions for the formation of self-accommodating processes are analyzed. [ABSTRACT FROM AUTHOR]

Abstract: The effects of three electrode materials – stainless steel (SS), pure titanium (PT), and titanium-based alloy (TA) – on the PEF-induced degradation, spectral characteristics, visual colour, and antioxidant capacity of cyanidin-3-glucoside (Cy-3-glc) and cyanidin-3-sophoroside (Cy-3-soph) were studied. Cy-3-glc and Cy-3-soph were degraded by PEF; SS retained Cy-3-glc and Cy-3-soph the most, while PT and TA led to greater degradation. Cy-3-glc was more susceptible to PEF than Cy-3-soph. The intensity of UV–Vis spectra absorbance at 520nm decreased, but it increased at 280 and 325nm after PEF when using the three electrodes. Their lightness (L ∗) exhibited no changes with SS, but showed a significant reduction with PA and TA. Redness (a ∗) significantly decreased with all three electrodes; the yellowness (b ∗) of Cy-3-glc with PA and TA, and of Cy-3-soph with SS, were also significantly reduced. The antioxidant capacity of Cy-3-glc and Cy-3-soph with SS, in contrast to PT and TA, was enhanced after PEF. [Copyright &y& Elsevier]

The most commonly used titanium (Ti)-based alloy for biological applications is Ti-6Al-4V, but some studies associate the vanadium (V) with the cytotoxic effects and adverse reactions in tissues, while aluminum (Al) has been associated with neurological disorders. Ti-Nb alloys belong to a new class of Ti-based alloys with no presence of Al and V and with elasticity modulus values that are very attractive for use as a biomaterial. It is well known that the presence of interstitial elements (such as oxygen, for example) changes the mechanical properties of alloys significantly, particularly the elastic properties, the same way that heat treatments can change the microstructure of these alloys. This article presents the effect of heat treatment and oxygen doping in some mechanical properties and the biocompatibility of three alloys of the Ti-Nb system, characterized by density measurements, X-ray diffraction, optical microscopy, Vickers microhardness, in vitro cytotoxicity, and mechanical spectroscopy. [ABSTRACT FROM AUTHOR]

Monocrystalline diamond structures (synthetic and naturally occurring), offer the potential to exploit the anisotropic characteristics of this material in cutting tools by enabling the best crystallographic orientation to be selected to suit the application conditions of the tool. This paper investigates the performance of monocrystalline chemical vapour deposition (CVD) diamond tools in micromilling of a titanium based alloy, Ti-6Al-4V. A comparison of single-blade milling cutters using two different crystallographic orientations is made on a high-precision four-axis miniature machine tool. Employing the cutting edges of the monocrystalline diamond with the rake/flank faces of {100}/{110} and {110}/{100} orientations respectively, the progressive wear of the tools has been micrographed, the coincidental workpiece surface quality assessed, and machined chips inspected. Examinations using scanning electron microscopy reveal clear differences in the predominant failure modes of the cutting edges: the {110} rake orientation showing abrasion; the {100} rake orientation showing fracture/cleavage. While the measured roughness (Ra, Rz) of the micromilled workpiece surfaces for the two diamond cutting edge orientations were not significantly different, the surface morphologies show the transition from cutting to tearing and dragging of the workpiece material. The analyses of tool wear and workpiece surface quality proved that monocrystalline CVD diamond cutting edges with preferential crystallographic orientation along rake and clearance faces can be successfully utilized for interrupted cutting operations (i.e. micromilling) of alloys which react with diamond, such as those based on titanium. [ABSTRACT FROM AUTHOR]

Abstract: Beta titanium alloys form one of the most versatile group of materials with respect to processing, microstructure and mechanical properties, mainly in applications as biomaterials. Development of new Ti-based alloys for implant application involves more biocompatible metallic alloying elements, such as Nb, Ta, Zr and Mo. Heat treatment of Ti alloys plays an important role in determining microstructure. The aim of this work is the analysis of microstructure and phases formed during water quenching of β Ti–20Nb alloy through different cooling rates. Ti–20Nb alloy was swaged at 780–860 °C and then machined as a cylinder. Cylindrical sample was treated within the β field and then water quenched from the bottom imposing different cooling rates through the sample. Samples from different regions (cooling rates) were characterized by using X-ray diffractometry (XRD), scanning (SEM) and transmission electron microscopy (TEM), and Vickers microhardness. XRD results showed the increase of β/α phases peak intensity ratio increase with decreasing of cooling rate. As the distance from the bottom (water source) of Ti–20Nb sample decreases, the imposed cooling rate increases, the volume of α martensite acicular phase increases and the size decreases with diminishing of α phase quantity. The lowest elastic modulus E =74 GPa was found for water quenched sample under a cooling rate of 160 K/s. [Copyright &y& Elsevier]

Abstract: The electrochemical and corrosion behavior of Ti-based alloys was investigated. The direct metal deposition technique was used to fabricate 21 alloys with different ratio of metals (0≤Al≤27wt.%, 0≤Fe≤25wt.%). Corrosion resistance of each alloy was evaluated both qualitatively and quantitatively by voltammetric measurements in the simulated human body fluid conditions (Hank''s solution). The corrosion rates of the materials were compared in Hank''s solution using Tafel extrapolation method. Among the Ti–xAl–yFe alloys the Ti–7Al–4Fe alloy exhibited the slowest corrosion rate of 7.7×10−4 mm/year and the least value of passive current density (6.3×10−3 A/m2). The alloy is resistant to pitting corrosion as well. [Copyright &y& Elsevier]

A friction- and wear-resistant Al–Cu–Fe–Cr quasicrystalline coating was fabricated on substrate of titanium alloy by low-pressure plasma-spraying (LPPS) method. The LPPS Al–Cu–Fe–Cr quasicrystalline coating has a rapidly solidified lamellar microstructure consisting of mainly decagonal phase and small amount of cubic phase peaks. The results showed that Al–Cu–Fe–Cr quasicrystalline coating improved the friction and wear resistance of titanium-based alloys under dry sliding wear test conditions. The excellent wear resistance may be attributed to the high hardness of Al–Cu–Fe–Cr quasicrystal. [Copyright &y& Elsevier]

The high-temperature oxidation behavior of titanium-based alloys coated with Al–Cu–Fe–Cr quasicrystal using the low-pressure plasma spraying (LPPS) method was studied. The results showed that Al–Cu–Fe–Cr quasicrystal line coating improved the oxidation resistance of titanium-based alloys. The weight gains at 750 and 800 °C for Al–Cu–Fe–Cr quasicrystalline coating are very low and the oxidation kinetics follows a parabolic law. During the oxidation period there is no evident spallation of the coating from the substrate. Oxide formed on the surface of Al–Cu–Fe–Cr quasicrystalline coating after oxidation consisted of Al2O3. [Copyright &y& Elsevier]

Ti-based alloys are widely used in medical applications. When implant devices are used to reconstruct disordered bone, prevent bone resorption and enhance good bone remodeling, the Young's modulus of implants should be close to that of the bone. To satisfy this requirement, many titanium alloys with different biocompatible elements (Zr, Ta, Mo, Si etc.) interact well with adjacent bone tissues, promoting an adequate osseointegration. Four new different alloys were obtained and investigated regarding their microstructure, mechanical, chemical and biological behavior (in vitro and in vivo evaluation), as follows: Ti20Mo7Zr15Ta, Ti20Mo7Zr15Ta0.5Si, Ti20Mo7Zr15Ta0.75Si and Ti20Mo7Zr15TaSi. 60 days after implantation, both in control and experimental rabbits, at the level of implantation gap and into the periimplant area were found the mesenchymal stem cells which differentiate into osteoblasts, then osteocytes and osteoclasts which are involved in the new bone synthesis and remodeling, the periimplant fibrous capsule being continued by newly spongy bone tissue, showing a good osseointegration of alloys. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay confirmed the in vitro cytocompatibility of the prepared alloys. [ABSTRACT FROM AUTHOR]

In view of the aging population and various diseases worldwide, the demand for implants has been rapidly increasing. Despite the efforts of doctors, engineers, and medical companies, the fabrication of and procedures associated with implants have not yet been perfected. Therefore, a high percentage of premature implantations has been observed. The main problem with metal implants is the mechanical mismatch between human bone and the implant material. Zirconium/titanium-based materials with graded porosity and composition were prepared by powder metallurgy. The whole samples are comprised of three zones, with a radial gradient in the phase composition, microstructure, and pore structure. The samples were prepared by a three-step powder metallurgy method. The microstructure and properties were observed to change gradually with the distance from the center of the sample. The x-ray diffraction analysis and microstructure observation confirmed the formation of diffusive connections between the particular areas. Additionally, the mechanical properties of the obtained materials were checked, with respect to the distance from the center of the sample. An analysis of the corrosion properties of the obtained materials was also carried out. [ABSTRACT FROM AUTHOR]

When used at high temperature in air, titanium-based alloys form an oxide scale at their surface but also dissolve large amount of oxygen in their metallic matrix and this is a cause of embrittlement. Nitrogen is a secondary oxidant, which also dissolves in and embrittles the alloy. Oxidation experiments of Ti-6Al-2Sn-4Zr-2Mo-0.1Si titanium-based alloy, for 1000 h at 650 °C in synthetic air (N 2 -20%O 2) and in a mixture of Ar-20%O 2 , showed that nitrogen decreases both oxide scale growth and oxygen dissolution. Atom probe tomography was used to investigate the alloy/oxide interface. The results revealed that the nitrogen effect is due to the formation of interfacial layers of oxynitrides and nitride (Ti 2 N), but also to the formation of a nitrogen rich α-titanium-based solid solution, which all act as diffusion barriers for oxygen, because of their low oxygen solubility. A comparison between the experimental results and thermodynamic calculations is also reported. [ABSTRACT FROM AUTHOR]