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|Paton B. Ye., Shpak A. P., and Ivasyshyn O. M. Basic trends of scientific investigations on titanium-related issues in Ukraine |
SUMMARY. The current status and future trends of R&D in the Ukrainian scientific institutions, aimed at creation of physical and metallurgical fundamentals of new titanium-based alloys and cost-effective technologies for their production and treatment are analyzed, allowing to improve service properties and thus, to provide wider application of these unique constructional materials are discussed.
|Fedirko V. M., Pohreliuk I. M., and Yaskiv O. I. Formation of functional coatings based on interstitial components under thermodiffusion saturation |
SUMMARY. Modern approaches to the protective coatings formation on titanium alloys surface based on binary and triple compounds using the method of thermodiffusion saturation have been analyzed. By summarizing the obtained result the prospect of priorities change in surface engineering from formation of binary compounds (oxides, nitrides, carbide) to triple ones (carbooxides, carbonitrides, oxynitrides) was substantiated in order to improve the service properties of the surface. The experimental results which confirm the advantage of coating based on triple compounds have been carried out.
|Firstov S. O., Kuzmenko M. I., Kulak L. D., Kotko A. V., Koval O. Yu., and Horna I. D. Structure and properties of high-modulus Ті–В alloys
SUMMARY. The effect of alloying with Al, Zr and Si on structure and mechanical properties including elasticity modulus of cast and deformed Ti–B alloys is studied. It is shown that optimization of compositions under combined silicide-boride strengthening of titanium alloys with additional alloying by aluminum can allow to obtain an elasticity modulus of about Е = 160 MPa, strength = 1500 МРа and plasticity = 2…5% at room temperature.
|Ilyin O. A., Skvortsova S. V., Mamonov А. M., and Kollerov М. Yu. The influence of hydrogen on phase and structural transformations in different grade titanium alloys |
SUMMARY. Regularities of phase and structure transformations in Ti-base alloys were investigated under the dissolved hydrogen action and during the following degassing. The possibility of control of structure formation process using hydrogen alloying in Ti-base alloys and obtaining the structure that could not be obtained by conventional technological techniques is shown. It was determined that alloying system defines the nature of Ti-base alloys-hydrogen interaction during hydrogen saturation. In Ti-base alloys with -isomorphic stabilizers (V, Nb) additional hydrogen alloying results in formation of intermediate hydrides, in the case of alloys with -eutectoid stabilizers (Cr) it results in formation of TiCr2 intermetallic, and in the alloys with higher content of aluminum it results in formation of Ti3Al intermetallic. It was shown that vacuum annealing of hydrogen-containing specimens at 600°С leads to formation of composite heterophase (++2) or (++TiCr2) structure in which intermetallic particles have an incoherent border.
|Liubin O. H. Life assessment of a tribosystem “shaft-bushing” |
SUMMARY. Based on solving the wear-contact problems life-times for couples nonwearing shaft–wearing bearing bush were evaluated. Results of numerical calculations of relative life-times are presented.
|Akhonin S. V., Mishchenko R. M., and Petrychenko I. K. Investigation of weldability
of titanium alloys, obtained by different melting methods
SUMMARY. The influence of the metal melting method (vacuum-arc and electron-beam melting with an intermediate capacity) on the properties and weald ability of titanium alloys is investigated. The weld ability of ВТ1-0 and ВТ6 alloys is shown to be practically independent on their melting method.
|Ostash O. P., Ivasyshyn A. D., Vasyliv B. D., and Okun’ I. Yu.
High-temperature and corrosion fatigue crack growth resistance of Ti–Si–Al–Zr alloys |
SUMMARY. The new Ti–Si–Al–Zr metal-matrix composites were the objects of investigations. It was established that high-temperature and corrosion fatigue crack growth resistance characteristics of the cast materials do not change up to the temperature of 700…800С and in 3% aqueous solution of NaCl (рН7) , respectively. Annealing and quenching of cast Ti–4Si–5Al–5Zr alloy from (+β)- and β-phase regions causing mainly matrix structure changes do not improve its strength and fatigue crack growth resistance in investigated environments except for the case of corrosion fatigue threshold increase after treatment from β-phase region and formation of lamellar -matrix . Increase of strength, plasticity and fatigue crack growth resistance of the composites at room and high temperatures is attained due to formation of globular structure of the matrix and silicide phase after thermomechanical treatment with deformation not less than 90%.
Riumshyna T. O., Volkova H. K., Loladze L. V., and Konstantinova T. Ye.Evolution of
Ti–5Al–5Mo–5V alloy structure deformed by high pressure
SUMMURY. The deformation features of Ti–5Al–5Mo–5V (ВТ22), alloy deformed by high pressure (cold extrusion, heat twist extrusion) are investigated by X-ray, optical and transmission electron microscopy depending on the phase state. It was shown, that the use of high pressure and complex deformation schemes jointly with temperature action allows the accumulation of the severe deformation without failure in the material. New structural states containing nanodimensional particles are formed in these conditions which cause the appearance of new properties. The deformation mechanisms on the mesolevel have been determined. It was established that under cold hydroextrusion the alloy which is in an amonophase state (100% β-phase) is deformed according to rotary deformation mechanism by formation of martensite phase. Deformation in two-phase α+β-alloy is realized by a bending mechanism. It is shown that the magnitude of elastic modulus essentially depends on the alloy initial phase composition and can be caused by the change of the deformation mechanism. During heat twist extrusion several deformation mechanisms operate. The knowledge of deformation mechanisms allows to choose purposefully the types of treatment and to create such a structure which provides a good combination of strength and plasticity.
|Zamkov V. M., Topolskyi V. P., Antoniuk S. L., and Moliar O. H. Development of a new system of high-strength titanium alloys alloying for welded constructions |
SUMMARY. Based on experimental data for redistribution of alloying elements between - and -phases during phase transformation and according to the concept of necessity to obtain equal molybdenum equivalent in different sites of -phase grain in cast condition, that is attained by complex alloying of titanium with -stabilizers having distribution factors higher and lower than 1, the alloying complex has been chosen and the alloying limits which provide high strength and weldability of a material was chosen. As a result of research work the chemical composition was developed,the operating modes of hot deformation, welding and heat treatment for new high-strength titanium alloy with high weldability were worked out on the basis of alloying system of Ti–Al–Mo–V–Nb–Fe–Zr.
|Shapovalova O. M. and Markova I. A.Investigation of the kinetics of b-phase decomposition in complex-alloyed titanium alloys |
SUMMARY. The serviceability of a welded joint (WJ) after ~19 104 h operation on thermal power station steam pipe-line was estimated according to the SINTAP procedure. The strength and fracture toughness parameters of the appropriate areas of WJ were used for calculation. It was assumed, that WJ was loaded by uniform tension, and in addition there were residual stresses in the WJ, and a semi-elliptical crack grows in the body metal and in the weld joint from external surface of the pipe. The critical state characteristics for the pipe element with WJ obtained using the calculation method, agree well with the expert conclusion about the reasons of steam pipe-line failure.
|Betsofen S. Ya. X-Ray methods for residual stresses measurement of gradient surface layers |
SUMMARY. The X-ray method of residual stress measurement in the surface layers of a variable chemical composition at a depth is developed. The method is based on measurement of lattice distances for various diffraction reflexes and separation of the contribution to the lattice distance size of elastic stresses and composition of a solid solution on the basis of features of elastic anisotropy of the crystal lattice of metals with cubic and hexagonal structures. Efficiency of the technique is shown on an example of ЭИ961 and 12Х18Н10Т steels and PT7M titanium alloy after ion nitriding and also of ЭП975ИД nickel superalloy after processing by electric erosion cutting.
Markovskyi P. Ye., Pishchak V. K., Mordiuk B. M., and Okrainets P. N. Improvement of fatigue characteristics of ВТ1-0 titanium alloy by surface mechanical and high-speed heat treatment |
SUMMARY. The influence of various regimes of thermo-mechanical and subsequent rapid heat treatments on surface layers hardening of the commercial pure titanium ВT1-0 was studied. It was found that the highest hardening level was obtained after treatment route that included vacuum annealing at 10–5 Pa, 800°C, 1h → surface deformation with ultrasonic impact treatment → rapid induction heating of surface up to 600°C. The evolution of structure in surface layers of ВT1-0 after this treatment was analyzed. It was shown that the fatigue limit increases by 50% as compared to the reference-annealed condition.
|Makhutov N. A. and Matvienko Yu. H.Experimental-calculation evaluation of elastic-plastic crack growth resistance of thin sheets |
SUMMARY. It has been shown that experimental-calculated methods are very useful for thin-sheet materials and thin-walled structures when the use of standard experimental methods is limited. The use of such methods for the evaluation of the contour J-integral and critical rstrain intensity factor in a thin plate with a crack has been illustrated. This approach is based on the dividing grids method, the deformation theory of plasticity and basic equations for considered fracture mechanics parameters.
|Yasnii P. V., Pshoniak P. V., and Okipnyi I. B. The influence of combined warm prestressing on brittle fracture of heat-resistant steel
SUMMARY. The influence of preliminary combined loading (which involves addition of a low-amplitude cyclic component to static tension at the stage of overstressing), on tension strength, crack tip opening displacement, and brittle fracture resistance of heat resistant 15Х2МФА steels after heat treatment which simulates materials embrittlement of the reactor case at the end of the reactor operation time is investigated. Tension strength was determined by uniaxial tension of cylindrical specimens of the working part diameter of 5 and 8 mm in liquid nitrogen. Compact tension specimens of thickness 19 mm were tested for tension according to the scheme heating – loading – unloading – cooling – fracture. The basic regularities of the influence of temperature, level and the amplitudes of a cyclic combined overload on the tension strength and critical stress intensity factor of 15Х2МФА steel are revealed. At a warm pre-stressing (WPS) temperature of 623 K, which is much higher than the brittle-to-ductile transition temperature for the given steel (Тbd = 390 K), the combined WPS increases the critical SIF, Kf, of 15Х2МФА steel up to 30% as compared to the static WPS. At a temperature of warm pre-stressing of 423 K, which is close to the brittle-to-ductile transition temperature for the given steel, the combined WPS decreases the critical SIF, Kf, of 15Х2МФА steel compared to the static WPS. The influence of the combined WPS on the critical SIF of 15Х2МФА steel prevails by two factors, namely, the crack tip opening displacement and changes in the tensile strength. At high temperature (623 K), dynamic creep is initiated at the crack tip, which leads to an increase in the crack tip opening displacement. On the other hand, an additional cyclic component decreases cleavage stresses compared to static loading under similar plastic strain.
|Nekliudov I.M. and Voievodin V. N. Problems of radiation stability austenitic steels |
SUMMARY. At present austenitic steels are the basic structural materials for cores and claddings of fast reactors for the first wall of thermo nuclear reactor (TNR). In this paper, results of the analysis of swelling behaviour of the alloyed austenitic stainless steels (ASS) are described from the point of view of the cooperative interaction of defect structure, solid solution decay and precipitates evolution. The role of alloying elements on evolution of structure, composition and its radiation stability under irradiation was investigated.
|Gabetta G. and Dietzel W. Knowledge management for environmentally assisted cracking problems|
|Macha E., Łagoda T., Niesłony A., and Kardas D. Fatigue life under variable-amplitude loading according to the cycle counting and spectral methods using the Serensen–Kogayev hypothesis||