Materials science
Change in the phase composition of an alloy based on titanium nickelide during the implementation of the shape memory effect
O.S. Alsaeva, D.E. Gusev, M.Yu. Kollerov, A.O. Snegirev, A.V. Shalin
The relationship between phase transformations during heating and cooling of a Ti-55.6% Ni alloy by mass in a state aged in various modes with its shape change during the implementation of a one-sided shape memory effect has been studied. It has been shown that after deformation at -10°C by 2% by bending, shape restoration occurs in two stages. In this case, one stage is characterized by a small (0.3–0.4%) value of the restored deformation, and the other – by a large one (1.0–1.1%). After two hours of aging at 520°C and two-stage processing at 520°C + 460°C, a small part of the deformation (0.3–0.4%) is eliminated at the low-temperature stage of shape restoration, and after aging at 460°C – at the high-temperature stage. X-ray diffraction studies showed that the extent of the first and second stages of shape change is determined by the sequence of occurrence and/or the superposition of R->B2, B19'->R and B19'->B2 transformations upon heating.
Keywords: shape memory effect, NiTi, phase composition, deformation, transformation.
On the possibility of predicting the long-term strength of titanium alloys based on strength equivalents for aluminum and molybdenum
Yu.B. Egorova, L.V. Davydenko, I.M. Mamonov, N.I. Dergileva
The results of statistical studies of the dependence of the , long-time rupture strength of sheets and rods made of titanium alloys on their chemical composition at temperatures of 200–600°C are presented. Based on a generalization of literature data, a comparison was made of the temperature dependences of the long-time rupture strength of titanium alloys of different classes. A regression relationship has been obtained that allows us to estimate the average typical value of 100-hour long-time rupture strength depending on temperature and strength equivalents for aluminum and molybdenum. The possibility of predicting the long-time rupture strength of α-, pseudo α-, α+β-titanium alloys with strength equivalents for aluminum of 2–16% and molybdenum of less than 5% at temperatures up to 500-550°C has been confirmed.
Keywords: titanium alloys, aluminum and molybdenum equivalents, strength properties, test temperature, long-time rupture strength, statistical studies, property prediction.
Metallographic and regulatory-technical issues in the production of pipes from titanium alloys
S.V. Serikov
Using examples of the production of hot-rolled and cold-deformed seamless pipes from titanium alloy PT-7M, a method for assessing their operational reliability is analyzed. It is proposed to revise the technical content of existing GOST, TU, OST for the production of pipes from titanium alloys in the light of new achievements in science and technology. The new approach is based on the principle of metal identification.
Keywords: identification of metals, specific work of fracture, impact strength, coefficient of dynamic viscosity, strain rate, temperature.
Manufacturing technologies
Investigation of temperature fields in Ti-6Al-4V titanium alloy rod rolling process
A.Yu. Postylyakov, A.A. Koksharov, D.L. Shvarts
Using the finite element method, the rolling process of a 45 mm round bar made of Ti-6Al-4V Eli alloy on a medium-grade mill 450 using the flat oval - ribbed (oval) and oval - circle systems was simulated. The temperature fields in the outlet sections of the calibers and pauses between passes were analyzed. A non-uniform nature of the temperature distribution with localization of heating in the inner central region of the strip was revealed. At the same time, during pauses, even of long duration, there is no significant equalization of temperatures across the cross section. It has also been established that the difference in average temperatures between the free and contact surfaces after rolling in ribbed grooves decreases, and after rolling in flat oval grooves it increases. In this case, smaller values occur on the former contact and free surfaces, respectively, which must be taken into account when measuring temperature in industrial conditions.
Keywords: shape rolling, system of rolls passes, titanium bars, Ti-6Al-4V Eli alloy, temperature field, finite element method.
Connection of titanium steam turbine structural elements by electron beam welding
V.V. Travin, A.I. Zmozhniy, G.A. Shevelev
The collaboration between PJSC «Kaluga turbine works» and Kurchatov NRC – CRISM «Prometey» allowed to develop and introduce technological processes of electron beam welding of pseudo-alpha titanium alloys into steam turbine equipment production. These processes provide required static strength and cyclical endurance of welded joints. The article contains the examples of practical electron beam technology using for production important assemblies titanium steam turbine unit.
Keywords: weldability, technological process, electron beam welding, titanium alloys, steam turbine, examples of using.
Processing technologies
Obtaining biomedical materials with biocompatible and biostable properties based on multilayer coatings
M.M. Grebenshchikova
High-strength titanium alloys are the main structural material for traumatology and orthopedics. Domestic industrial alloys contain vanadium and molybdenum, which are toxic. Condensation of thin-film titanium hafnium nitride coatings with a layer thickness of 6–20 nm makes possible to reduce the transition of alloy ions into body tissue and increase the biocompatibility of the material. The developed method is based on the ion-plasma formation of multilayer coatings of titanium hafnium nitrides in a nitrogen atmosphere at a pressure of 0.1 Pa with short-term exposure to metal plasma and condensation of a nano-sized phase of hafnium nitride on the surface.
Keywords: titanium alloys, biological compatibility, titanium hafnium nitrides, ion plasma method, nano-sized phase of hafnium nitride
Approbation of low-temperature ion nitriding technology for monowheel imitator made of titanium alloy Ti-6Al-4V
A.F. Tagirov, R.D. agzamov, V.V. Astanin
The results of experiments on the process of low-temperature ion nitriding of a monowheel sector simulator made of titanium alloy Ti-6Al-4V in a glow discharge are presented. The results of microhardness by depth of the modified layer, microstructure, residual stresses in the surface layer of the blade samples are presented. The results of the coating adhesion study by scratch testing technique are presented.
Keywords: titanium alloy, ion nitriding, microhardness, residual stresses, coating.
Application. Quality. Market
Current problems of the use of titanium alloys for the production of intraosseous dental implants (review)
Y.N. Kusakina, L.V. Fedorova
The paper considers topical issues of the use of titanium alloys as materials for the manufacture of intraosseous dental implants. The concept of this work implies an overview of various aspects of the use of titanium alloys, both unalloyed, such as Grade 4, and various alloying systems, for example titanium-aluminum-vanadium, titanium-niobium-zirconium, titanium-niobium-tantalum as biologically compatible materials. Various surface treatment technologies of titanium implants providing the process of osseointegration are also presented, including both traditional technologies of air-abrasive treatment followed by acid etching, and innovative surface structuring technologies, including surface treatment with an ytterbium laser, plasma electrolytic oxidation technologies, as well as the use of bioactive electrochemically deposited calcium phosphate coating.
Keywords: titanium alloys, nanostructural state of titanium alloy, dental implants, surface treatment, biologically compatible materials.
