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Welding thermomechanically-strengthened materials is accompanied with certain difficulties in terms of loss of strength characteristics in the zone of thermal influence. This issue can be resolved by using the technological welding schemes that include fusion of materials in a narrow contact area. One such technological scheme is electron beam welding, which is currently widely used to fabricate structures from refractory and chemically active materials. One of the main advantages of the electron beam welding process is a small quantity of heat input, which leads to the formation of narrow zones of melting and thermal influence and, as a result, minor deformities in the structure of the material. The welded joint can structurally be divided into several zones, which differ in the morphological characteristics of the structure. The most interesting, in terms of ensuring the quality of the joint, are the boundaries between the zones. It has been shown that the use of local heating sources, which is the case at electron beam welding, leads to the migration of the boundaries of grains. As a result, clear intersections, fusion lines, form at the boundaries between zones of the welded joint. The formation of the structural state of a welded joint is predetermined by the simultaneous course of several processes. First, a crystallization from the liquid state – the formation of a welded joint structure, as well as the boundary between a welded joint and the zone of thermal influence. Second, the phase-structural transformations in the solid state – a thermal impact zone, the boundary between a thermal impact zone and the main metal. Given this, one should note that the geometry and quality of joints at electron beam welding are more interrelated than in other welding techniques. Thus, one of the main parameters that ensure the quality of a welded joint is the structural state of the material that forms during welding

Analysis of fracture surfaces morphology of material of welded joints of Ti-TiB system alloys and (α + β) Тi alloy, obtained by electron-beam welding under various technological modes, is carried out. Parameters alterable were the electron beam displacement velocity and initial temperature of the parts welded. Prevalent effect of boron phase on fracture character of Ti-TiB system alloys and possibility of ductility increase both Ti-TiB system and (α+β Тi alloy, due to thermal effect action, is shown.

An article present the result of macrostructure formation with distribution of mechanical properties in cross-sections of 8 mm-thick one-sided butt-welded FSW joints of EN AW 6082-T6 alloy which were obtained using three types of specially designed tools: C-type – conventional tool consisting of a housing, cylindrical threaded probe and a shoulder with a grooved spiral, T-type – Triflute-type tool consisting of a housing, cylindrical threaded probe with three grooves and a shoulder with a grooved spiral, S-type – simple tool consisting of a housing, smooth cylindrical probe without a thread and a flat shoulder. Friction stir welding was performed using equipment of the Institute of Welding in Gliwice of Poland, and mechanical tests in the E.O. Paton Electric Welding Institute of the NAS of Ukraine. Mechanical test by indentation was performed using Micron-gamma device, which allows experimental identification of structural state of metal and determination of the strain hardening presence by limiting values of ratio of hardness to Young’s modulus of elasticity. It was found that for all three specimens the HAZ hardness decreases, and in the zone of thermomechanical effect the hardness increases. Maximum hardness values are inherent to the central part of welded joint nugget, as well as to light-coloured oval concentrated fragments of structure in the nugget upper and lower part. Judging by the presence of nanosized hardened structure and uniformity of its distribution in the nugget, as well as good dispersion of oxide films and absence of discontinuities, the friction stir welding with C-type tool can be regarded as the optimum variant. An assumption was made that formation of a uniform structure in welds can be achieved at three–four revolutions of the tool in friction stir welding in one place. The model of thermal fields distribution in Al-plate during FSW using a C-type tool visualized the metal’s thermal condition when formated hardened nano-dispersed weld zones.

To improve the structure of metal in welded butt joints of railway rails produced by flash-butt welding and increase the reliability of butt joints, it is advisable to carry out their induction heat treatment using high-frequency currents. Solving the problem of a uniform bulk heating of weld metal of railway rails in a narrow area during its heat treatment remains an urgent task. The work describes the principle of designing an inductor without magnetic cores for carrying out a uniform bulk heat treatment of welded butt joints of railway rails for realization of favorable phase transformations of metal and normalization of its structure. The principle is based on the physical laws of propagation of electromagnetic fields and electric currents in the inductor and a rail. Based on the carried out investigations, an inductor was designed that has a variable shape along the perimeter of a rail and a variable distance from it, as well as a partial splitting of the inductor busbar for current parallelization, which provides a uniform bulk heating of a rail butt joint. Splitting of the inductor busbar allowed adjusting the propagation of currents in the inductor and a rail in such a way as to avoid overheating of a rail in its particular areas without a significant increase in the distance between the inductor and a rail, and respectively without a significant increase in the reactive power of the “inductor-product” system. The carried out experiments on heating the welded butt joint of a rail by the designed inductor showed the indices of uniformity and rate of its bulk heating, which are acceptable for heat treatment of rails both on the surface as well as in the depth of a rail in a narrow heating zone with providing the required temperature levels.

It was revealed that spatial position during laser welding of AISI 321 stainless steel influences the processes in the weld pool and the process of its crystallization. The geometry, structure, distribution of chemical elements depend on the cooling rate of the welded joint, which varies in different spatial positions during laser welding of stainless steel AISI 321. To achieve the lowest variance of results and the maximum values of mechanical characteristics of the welded joints of AISI 321 stainless steel it is recommended to produce laser welding in a vertical position.

The basic regularities and ways of optimizing the production of welded joints of Ti – TiB alloy plates and 12Х18Н10Т steel were studied. The ways to achieve the necessary mechanical characteristics of welded structures from elements with a thickness of 10 mm obtained by electron beam welding were found out. It was determined that electron beam welding of Ti – TiB alloy compounds with 12Х18Н10Т steel is effective when using a double strip of niobium and 10Г2 steel. It was found that in order to obtain welded joints of the Ti – TiB alloy with Nb electron beam welding, it is necessary to ensure the melting of the Ti – TiB alloy, conditions for wetting niobium with the obtained melt, and to prevent the formation of an intermetallic layer in the weld. It is shown that the welded joint Ті-TiB - Nb - 10Г2 - 12Х18Н10Т obtained by electron beam welding allows to achieve a strength level of at least σв = 260 MPa.

The article presents the results of studying the surface layers of structural steel samples alloyed with 48(WC–W 2 C) + 48Cr + 4Al powder materials mixture using laser-plasma alloying technology. ROFIN-SINAR Nd:YAG-laser DY044 (Germany) with irradiation wave length λ = 1.06 μm was used for laser alloying. Equipment and technologies of laser-plasma alloying were developed at the E.O. Paton Electric Welding Institute. Detailed studies at all structural levels of grain, subgrain, dislocation structures, including phase precipitates and their stoichiometric composition, were carried out using optical, scanning electron, and microdiffraction transmission electron microscopy. It was found that the formation of crack concentrators in the treated surfaces is due to such structural factors as coarse-grained structure, chemical inhomogeneity, and the formation of dislocation density gradients in grain-boundary areas. Under the optimal mode of laser-plasma alloying of the treated surfaces, a fine-grained structure is formed with a uniform distribution of the dislocation density. In this case, the dislocation substructure is characterized by a cellular type with a cell size of 50…110 nm and by the presence of dispersed phase precipitates up to 100 nm in size in the internal volumes of grains. Dispersion of the structure, the formation of a non-disoriented cellular dislocation substructure with a uniform distribution of dislocation density, the presence of dispersed phase precipitates (nanoscale type) will contribute to an increase in crack resistance and strength characteristics due to substructural and dispersion hardening.

In this article, structural features of Ti-TiB and (&alpha, +&beta, ) Ti alloys in the initial state, in the weld and in the heat-affected zone of electron beam welds were investigated. The influences of welding parameters, such as influence of the electron beam velocity, preheating of the welded alloys and the subsequent annealing of the welded joint on the its microstructure, and the mechanical strength and ductility of the critical elements of the joint were studied by scanning electron microscopy using microprobe Auger spectral and X-ray diffraction analysis and tensile tests. It has been shown that the conditions for rapid crystallization of the material from the melt of the weld contribute to refining of reinforcing fibers of TiB and its hardening in comparison with the starting material Ti-TiB. Besides that, influences of the preferential orientation of TiB reinforcing microfibers (along and across the welded butt joint) on the mechanical properties of the welded joint were investigated bz tensile testing. Using the methods of fractographic analysis, the effect of the boron-containing phase on the fracture character of Ti-TiB welded joints was established. It was shown that, along with the strengthening effect, TiB fibers cause embrittlement of the material.

The article presents test results concerning the structure of welds made of high strength low-alloy steel 14HGNDC which, in the molten state, was provided with nanoparticles of various refractory compounds including oxides, carbides, and nitrides (TiC, TiN, SiC, VC, NbC, TiO2, Al2O3, MgO and ZrO2). The performed tests revealed the effective use of the nanooxides of titanium (TiO2) and zirconium (ZrO2) enabling the obtainment of high mechanical properties of the weld metal (Rm—708 MPa and 621 MPa, KCV-20—60 J/cm2 and 72.9 J/cm2, a—21 and 19%). The use of a Gleeble 3800 welding cycle simulator made it possible to determine the dependence between temperature ranges of transformations, amount of structural constituents and types of modifying nanoparticles.

Досліджувалися можливості отримання зварного з'єднання сплавуТі-TiB заустенітної сталлю 12Х18Н10Т шляхом формування проміжного шару в зварному з'єднанні. Для цього на поверхні зразка сплаву Ті-TiB формувався легований прошарок, що містить армуючі волокна TiB і основні легуючі елементи стали 12Х18Н10Т. Було визначено, що такий прошарок одержується застосуванням електронно-променевого зварювання з'єднання сплаву Ті-TiB з ванадієм через фольгу зі сталі 12Х18Н10Т. Було виявлено, що мікроструктура сформованого прошарку сплаву на основі титану іванадію з легуючими добавками має характер металевої матриці, армованої мікроволокнами, склад яких відповідає боріду титану, легованого ванадієм. Було виявлено, що для армуючих боридних мікроволокон в мікроструктур і прошарку сплаву на основі титану і ванадію характерною особливістю є їх значне подрібнення в порівнянні з вихідним сплавом Ті-TiB. Крім того, в цьому прошарку в зоні розпаду первинних борідів титану, ініційованого впливом електронного променя, були виявлені фазові утворення за елементним складом близькі Ti2B. В результаті було зроблено припущення, що прошарок сплаву на основі Ti (63-68 at.%) І V (18-25 at.%) із легуючими добавками (Fe, Cr, Ni, B, C), сформований на поверхні сплаву Ті -TiB, перспективний для використання для електронно-променевого зварювання сталі 12Х18Н10Т зі сплавом Ті-TiB. Possibilities of obtaining and using an intermediate layer for joining of Ti-TiB and austenitic steel 12X18H10T (analog of AISI 321; 1.4541; X10CrNiTi18-10) were studied. An alloyed interlayer with TiB reinforcing fibers and the main alloying elements of 12X18H10T steel was formed on the surface of the Ti-TiB sample. Such interlayer was formed during electron beam welding of Ti-TiB with vanadium using foil made of 12X18H10T steel. The microstructure of the interlayer consists of a metal matrix reinforced with microfibers. It’s composition corresponds to vanadium-alloyed titanium boride. In comparison to the initial Ti-TiB alloy, significant grinding of reinforcing boride microfibers in the interlayer microstructure was observed. Besides, the phase formations close to Ti2B in zone of primary titanium borides decomposition in the interlayer, initiated by electron beam were determined. As a result, application of Ti (63–68 at. %) and V (18–25 at. %) based interlayer with alloying additives (Fe, Cr, Ni, B, C) has great potential for utilization in electron-beam welding of 12Х18Н10Т steel with Ti-TiB alloy. Исследовались возможности получения и использования промежуточной прослойки для выполнения сварного соединения сплава Ті-TiB с аустенитной сталью 12Х18Н10Т (аналоги AISI 321, 1.4541, X10CrNiTi18-10). Для этого на поверхности образца сплава Ті-TiB формировалась легированная прослойка, содержащая армирующие волокна TiB и основные легирующие элементы стали 12Х18Н10Т. Было определено, что такая прослойка получается применением электронно-лучевой сварки соединения сплава Ті-TiB с ванадием через фольгу из стали 12Х18Н10Т. Было выявлено, что микроструктура сформированной прослойки сплава на основе титана и ванадия с легирующими добавками имеет характер металлической матрицы, армированной микроволокнами, состав которых соответствует бориду титана, легированногованадием. Былообнаружено, что для армирующих боридных микроволокон в микроструктуре прослойки сплава на основе титана и ванадия характерной особенностью является их значительно еизмельчение в сравнении с исходным сплавом Ті-TiB. Кроме того, в этой прослойке в зоне распада первичных боридо втитана, инициированного влиянием электронного луча, были обнаружены фазовые образования по элементному составу близкие Ti2B. В результате было сделано предположение, что прослойка сплава на основе Ti (63–68 at. %) и V (18–25 at. %) с легирующими добавками (Fe, Cr, Ni, B, C), сформированная на поверхности сплава Ті-TiB, перспективна для использования для электронно-лучевой сварки стали 12Х18Н10Т со сплавом Ті-TiB.

Проведен анализ морфологии поверхностей разрушения материала сварных соединений сплавовсистемы Тi–TiB и (α+β) Тi сплава, полученных способом электронно-лучевой сварки при различныхтехнологических режимах. Изменяемыми параметрами были скорость перемещения электронноголуча и исходная температура свариваемых деталей. Показано превалирующее влияние борсодержащей фазы на характер разрушения сплавов системы Тi–TiB и возможность увеличения пластичности как сплава системы Тi–TiB, так и (α+β) Тi сплава за счет термического влияния.