Papers by Keyword: Titanium

Abstract: Titanium alloys due to their low density and high mechanical properties are a group of materials that are being used willingly nowadays. A promising method of titanium heat treatment is laser surface alloying. Process parameters like laser beam power, its transverse speed, amount of alloying elements and shield gas, have influence on the material. Different chemical composition and morphology can be achieved resulting in a change of properties on the surface of the material. The paper presents the investigation of titanium GRADE 1 processed with iron‐nickel powder using laser alloying. The treatment was performed using a high power diode laser. Different laser beam power values were used.

Abstract: Superplastic forming is a cost-effective process for manufacturing complex-shaped titanium parts. TIMETAL^® 54M (Ti54M) is a titanium alloy that has been commercially available since 2003, however studies on modelling its superplastic behaviour are scarce in the literature. Finite element modelling can be used to enable the manufacturing of complex-shaped parts economically as the number of experimental trials can be reduced. This paper illustrates the implementation of a microstructural-based model to predict the superplastic behaviour of Ti54M alloy during forming at elevated temperature. The parameters of the material model are derived in this work for the Ti54M alloy. A Matlab script has been developed for the calculation and calibration of the material model parameters based on material experimental data. The material model was implemented into the finite element commercial software Abaqus by means of a user-defined subroutine. The finite element calculations take into account also grain size evolution. Finally, a pressure profile was numerically calculated for forming a non-commercial part via superplastic forming targeting optimal conditions for the material.

Abstract: The Article presents the findings of the studies of the microstructure, chemical and phase composition of the Cr₃C₂-Ti system alloys obtained by the explosion. Scanning electron microscopy, energy dispersive and x-ray diffraction analyses were used. The program Thermo-Calc software was used to calculate the equilibrium phases. The phase composition of the compact was shown to fully correspond to that of the initial powder mixture during explosive pressing in the modes of heating from 300 ̊С to 600 ̊С. When heated above 600 ̊С, the chemical interaction of the initial components begins with the formation of new boundary phases. Meanwhile, there is a change in the sample destruction nature and a significant increase in hardness, which points to the hard alloy consolidation. The increase in the powder mixture heating in shock waves to 1000 ̊С leads to intensive macrochemical interaction of the powder mixture components and to formation of an equilibrium phase composition. The established temperature limits determine the most appropriate parameters of shock-wave loading when producing hard alloys by explosive pressing.

Abstract: Transmission electron microscopy investigations were carried out to study the structural-phase state of ultra-fine grain (UFG) titanium with the average grain size of ~0.2 μm, implanted with aluminum ions. Implantation was carried out on MEVVA-V.RU ion source at room temperature, exposure time of 5.25 h and ion implantation dosage of 1⋅10¹⁸ ion/cm². UFG-titanium was obtained by a combined multiple uniaxial compaction with rolling in grooved rolls and further annealing at 573 К for 1h. The specimens were investigated before and after implantation at a distance of 70-100 nm from the specimen surface. Concentration profile of aluminum implanted with α-Ti was obtained. It was revealed that the thickness of implanted layer was 200 nm, while maximum aluminum concentration was 70 at.%. Implantation of aluminum into titanium has resulted in formation of the whole number of phases having various crystal lattices, like β-Ti, TiAl₃, Ti₃Al, TiC and TiO₂. The areas of their localization, the sizes, distribution density and volume fractions were determined. Grain distribution functions by their sizes were built, and the average grain size was defined. The paper investigates the influence of implantation on the grain anisotropy factor. It was revealed that implantation leads to the decrease in the average transverse and longitudinal grain size of α-Ti and decrease in the anisotropy factor by three times. The yield stress and contributions of separate strengthening mechanisms before and after implantation were calculated. The implantation has resulted in increase in the yield stress by two times.

Abstract: TiNb coatings were obtained by the electro-explosive doping on the surface of a titanium dental implant (VT6 alloy). The elemental and phase composition was determined by the methods of scanning and transmission electron microscopy and by X-ray structural analysis. The morphology and defective substructure of the coating were studied. Hardness and Young's modulus, friction coefficient and wear resistance of the formed coating were determined. It has been established that the electro-explosive coating is multi-element and multi-phase and possesses submicro-and nanocrystalline structure, high strength and tribological properties. It was found, that the formation of TiNb coating is accompanied by a multiple (more than 2 times) decrease in the wear parameter, i.e. wear resistance increase of the surface layer, an increase in the friction coefficient by 1.5 times, significant increase in hardness (1.5 times) and Young's modulus (1.3 times).

Abstract: This study investigates the microstructure and the solidification behavior of titanium-alloyed gray irons. Thermal analysis technique was used to identify the Temperature of Liquidus Arrest (T_LA), the Temperature of Eutectic Undercooling (T_EU) and the Temperature of the Eutectic Recalescence (T_ER). It was found that the titanium addition promoted the formation of the primary austenite causing the larger difference in T_LA and T_EU. In addition, titanium encouraged the refining of eutectic mixture. The SEM showed the graphite particles were refined with increasing titanium. Fine particles of titanium-containing compound were readily observed throughout the microstructure. The hardness as high as 176 HB was achieved at 0.495%Ti addition.

Abstract: Surface wettability is thought to influence the osteoconductivity of bone-substituting materials; however, the effects of surface wettability on osteoblast behavior are not well understood. In this study, we prepared both an as-polished pure titanium with a water contact angle (WCA) of 57° and heat-treated pure titanium with more hydrophobic surface and WCAs of 68°-98°. The effects of the surface wettability of pure titanium on osteoblast behaviors were evaluated by in vitro assays. Compared with the as-polished titanium, the proliferation rate of osteoblast increased on heat-treated titanium. This suggested that surface wettability affects osteoblast behaviors, meaning osteoconductivity is influenced by surface wettability.

Abstract: Ti-Mn alloy has a high specific strength, excellent cold workability and good biocompatibility. A cold rolled Ti-7 wt.% Mn was compared to annealed sample at 900°C for 10 min and the corrosion resistance property was tested in artificial saliva solution (AS). The Ti-7 wt.% Mn alloys (cold rolled and annealed) were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX) and compared to pure Ti. Simultaneously, the alloys tested in the AS solution for up to 28 days mainly by following the open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), SEM and EDX. Annealed Ti-7wt.% Mn showed good corrosion properties similar to that of pure Ti, hence the new Ti-7wt.%Mn alloy have higher specific strength than pure Ti, yet showed same corrosion properties which favor implanted dental applications.

Abstract: It is shown that micro-arc oxidation (MAO), implemented according to traditional schemes in electrolytic baths with mechanical and pneumatic mixers, does not provide the formation of uniform ceramic coatings on the surfaces of holes, grooves and slots in the details from the alloys of the metals of valve group, and is characterized by a significant cost and relatively low safety. Fundamental possibility of MAO realization in the inner cavities of the special counter electrodes by passing solutions of electrolytes through them is installed. The calculated and experimental researches of MAO, applied to the processing of ball details from aluminum and titanium alloys, are conducted. The most rational design parameters of counter electrodes, as well as the rational parameters of the flow of electrolyte solutions in the clearances between the surfaces of details and counter electrodes are revealed. Innovative schemes for MAO of spherical details are developed. By measuring the thickness and hardness of the formed coatings it is proved that MAO, in the internal cavities of the counter electrodes, provides for the formation of more uniform ceramic coatings on the details from alloys of valve metals, in comparison with the traditional MAO in electrolytic baths with pneumatic and mechanical mixers.

Abstract: Improving the quality of hardware through the improvement of the microstructure is one of the main trends of modern metallurgy. This approach allows us to achieve special properties without the expense of expensive alloying additives. The basic idea is to grind the grain structure of the material to a size less than 1 μm. At the specified grain sizes, the hardening properties begin to manifest with a relatively small loss of plasticity. In this case, one can speak of ultrafine-grained (UFG) materials. This direction is especially important for areas of science and technology, where there are very strict requirements for the size and weight of parts with their high strength. These are aerospace engineering and medicine (implantology and orthopedics). Therefore, it makes sense to conduct research primarily on relevant materials. Titanium is known for its biological inertness, therefore it is the basis for prosthetics. In this work, the experiments on technically pure titanium using a technology close to industrial implementation, were performed. An experiment, in which a lengthy number billet at a temperature of 500 °C rolled from a diameter of 30 mm to a diameter of 15 mm in the mill SVP-08, was conducted. After that, the billet was cooled with water, and samples for studying the microstructure and samples for studying the mechanical properties, were prepared. Analysis of the microstructure showed the presence of an equiaxial ultrafine-grained structure in the peripheral areas of the work-piece and the presence of an elongated fibrous texture in the axial zone. The strength of the work-piece has increased by more than 1.5 times, while the plasticity has decreased not so much.