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Experimental laboratory equipment for friction stir welding (FSW) as a result of working out the optimal welding modes at different linear velocities allows producing high-quality butt joints from thin ductile metals. With the development of new mathematical methods for modeling thermodeformational processes, it became possible to analyze the stress-strain state and thermo-mechanical processes occurring in the FSW joint zone, which is necessary for predicting the operational properties, strength and service life of welded structures made of thin metal. Using mathematical models and finite element analysis, the temperature distributions from the volume heat source at FSW were visualized, and the residual deformations and stresses in the zone of butt-welded joints of thin sheets of magnesium alloys were numerically determined. In the future, it is advisable to determine the effective balance of the linear speed and the rotation speed of the FSW tool to obtain better homogeneity of the weld structure and reduce heat input into the metal during welding. [ABSTRACT FROM AUTHOR]

An installation for obtaining isotopes using the intense internal beam of protons on the U-240 cyclotron has been developed. A target was designed to produce the 22Na isotope under difficult conditions of thermal and radiation loads in a limited space of the cyclotron accelerator chamber. Radiochemical isolation of the 22Na isotope was carried out. [ABSTRACT FROM AUTHOR]

The article analyzes the results of research of structural features and tensile strength of butt joints of 2 mm thick sheets of structural MA2-1M magnesium alloy produced by argon arc welding with a non-consumable electrode and by friction with stirring. It is shown that in friction stir welding as a result of intense plastic deformation of the metal, a fine crystalline structure is formed in the welds. It was determined that microhardness of the metal in such a welded joint has minimum values in the zone of thermomechanical effect on the side of the deviation near the heat-affected-zone, where the fracture of the specimens occurs during their static tension. Tensile strength of specimens of welded joints produced by friction with stirring, and specimens with penetrations removed to the level of the base material and additionally cleaned reinforcements of welds produced by melting, is at the level of 233...236 MPa, which amounts to ~84% of this index for the base material. Ref. 13, Tabl. 1, Fig. 6. [ABSTRACT FROM AUTHOR]

The paper gives the results of investigations on vacuum diffusion welding of МА2-1 magnesium alloy. Different technological measures were used in welding: unsupported welding, welding with application of forming matrices, welding without interlayers and with a zinc interlayer. It is found that it is not possible to produce the joint in unsupported welding without an interlayer at 400 °С temperature and process duration less than 60 min. Increase of welding temperature or time leads to considerable grain growth. Application of 250 ~m zinc interlayer and of the following welding mode: Т = 320 ºС, Р = 10 MPa, t = 30 min allows producing the joint. Analysis of chemical composition in different areas of the joint zone shows that development of diffusion processes in the butt during welding results in pore formation with magnesium content on the level of 17.8 – 20.12 wt. % in the zinc interlayer at 2 – 3 ~m distance from magnesium/zinc contact line. In the central part of the joint zone the metal chemical composition is close to pure zinc composition. Application of forming matrices and an interlayer of zinc in the solid-liquid state in welding in the following mode: Т = 340 ºС, Р = 10 MPa, t = 30 min. allows producing sound joints due to localisation of plastic deformation in the butt joint. Results of metallographic investigations showed formation in the butt joint of common grains and remains of the interlayer in the form of dispersed particles of 15…50 ~m size, with chemical composition of Mg–4.53Al–0.20Mn–63.49Zn, wt. %, having an irregular elongated shape. [ABSTRACT FROM AUTHOR]

The possibility of manufacturing thin foils of high-entropy alloys (HEA) of Co‒Cr‒Fe‒Ni‒Si system by the method of highspeed (up to 10 μm/min) electron beam physical-vapour deposition (EB-PVD) is shown in the work. It was established that silicon content in the alloy composition of approximately 5 wt.% improves the values of high-temperature resistance of basic CoCrFeNi HEA. It is shown that at soaking in air for 28 h at the temperature of 1000 °C the specific change in the weight of CoCrFeNiSi0.2 sample is not more than 0.9 mg/cm². A technological scheme was proposed of manufacturing by welding three-layer thermal protection honeycomb panels with a low specific weight based on thin foils of high-entropy CoCrFeNiSi0.2 alloy. It was found that the produced by the proposed scheme three-layer thermal protection panels can stand multiple thermal cycling from 25 to 1000 °C in air without the structure failure. The derived results can be the base for development of the technology of manufacturing lightweight honeycomb structures, capable of ensuring thermal protection of aerospace equipment elements at their interaction with the atmosphere. [ABSTRACT FROM AUTHOR]

The paper presents the results of investigations on diffusion welding of high-temperature alloy EI437B, using foil from high-entropy alloy of CrMnFeCoNi system as an interlayer. The features of producing foil from high-entropy alloy and its main physical-chemical properties in as-rolled and as-annealed condition are given. Increase of the degree of the foil general deformation to 99.9 % results in up to three times increase of the yield limit, and further annealing of the foil leads to its lowering to values characteristic for EI437B alloy. During diffusion welding the Young’s modulus increased from 165 to 195 GPa in the joint zone corresponding to the high-entropy alloy, which may be indicative of a diffusion-induced redistribution of elements in the interlayer. Chemical element distribution in the joint zone is indicative of their sufficiently high diffusion mobility. It is shown that application of a high-entropy alloy interlayer in vacuum diffusion welding ensures formation of a diffusion zone of a rather homogeneous chemical composition with a monotonic nature of distribution of the main alloying elements. The thermo-deformational impact results in equalizing of the characteristics of hardness and modulus of elasticity in different regions of the joint, and their physical-mechanical properties become similar. [ABSTRACT FROM AUTHOR]

A literature review of the current state of magnesium alloy production technology is given, alloy properties and the influence of alloying elements on them are analyzed, microstructure and the main phases forming in the cast and wrought magnesium alloys are determined, a classification of modern magnesium alloys of foreign production is presented, further paths of their development are outlined, and problems in magnesium alloy application are defined. Magnesium alloying by other elements (Al, Mn, Zn, Si, Re, etc.) or strong nanoparticles allows significant improvement of its existing properties so as to expand its scope of application. Current problems in magnesium alloy application (flammability, combustibility, surface durability, biosolubility, corrosion resistance, weldability) are solved by alloying, controlling the chemical and structural-phase composition, application of the respective modes of thermomechanical treatment and surface hardening. Ref. 27, Tabl. 2, Fig. 9. [ABSTRACT FROM AUTHOR]

Investigations on vacuum diffusion welding of nichrome powder alloy Ni-20Cr--(3--4)Fe--(0.40--0.6)Al--(0.25--035)Ti--0.5Y (% wt.), are presented. As shown, welding nichrome alloy directly in the temperature range of 800-1100°C under vacuum of 1.33 10-3 Pa does not provide sound joints. As found, during nichrome alloy heating, oxidation of its contact surfaces takes place, which makes it more complicated to produce the welded joint. The possibility of protection of the alloy surfaces from oxidation by coating them with nickel is studied. Deposition of a nickel interlayer by EBPVD method in the form of 5-7 µm thick coating allows avoiding oxidation of the contact surfaces. The influence of heat treatment in vacuum on the coating chemical composition is investigated. As shown, annealing of the coated samples at T = 1100°C for 10 min. under vacuum of 1.33 10-3 Pa promotes enhancement of the diffusion processes between the base metal and deposited nickel layer and ensures equalizing of the chemical composition in the zone of contact of the coating and the alloy. As shown, the microstructure of the samples, produced in the following mode: T = 1200°C, P = 40 MPa, t = 20 min is characterized by absence of defects in the joint zone. Distribution of chemical elements in the welded joint is monotonic. Diffusion of elements from nichrome alloy into the nickel coating ensures formation of the diffusion zone, is similar, in its chemical composition to nichrome alloy. Mechanical properties of the welded joints are studied. As demonstrated, application of an intermediate nickel layer at vacuum diffusion welding of a nichrome powder alloy enables producing joints with the microhardness on the level of that of the base metal after annealing. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies on production of layered composite materials, based on aluminium and titanium alloys, by vacuum diffusion welding, with a broad range of specific weight values, which is achieved due to different layer ratio in each of the composites. Based on a layered composite material, a procedure was proposed for manufacture of three-layer honeycomb panels by vacuum diffusion welding. It is found that the average compressive strength of the three-layer panel with a filler from a layered composite material based on Al–Ti alloys is equal to 47.3 MPa, that is four times higher that the strength of similar honeycomb elements made from an aluminium alloy. It is shown that the layered material has higher thermal stability, compared to aluminium alloys. Sample annealing at the temperature of 700 °С for 30 min does not lead to their early destruction or loss of shape. [ABSTRACT FROM AUTHOR]

The regularities of joint structure formation in diffusion pressure welding through multilayer interlayers based on AL-Si and Al-Cu aluminum systems with eutectic, obtained by electron beam deposition in vacuum, were studied, using SiCp-AMg5 aluminum composite, as an example. It is shown that the intermediate multilayer layers of eutectic ‘composition provide permanent joints without degradation of the properties of the base material at a temperature of 500 °C, which corresponds to the beginning of intensive plastic deformation of the interlayer under pressure. It is established that the nature of the diffusion interaction of the components of the interlayer and the composite and the phase composition of the eutectic affect the structure and the chemical composition of the joint. Conditions that prevent the formation of barrier layers at the interlayer/composite interface, namely layer alloying or intermetallic particle formation in it before the welding process, promote intensive mass transfer of interlayer and composite components, ensuring homogeneity of the structure and microhardness of the joint. Mechanisms for forming SiCp-AMg5 composite joint through multilayer intermediate layers based on aluminum systems with eutectic of different types — simple, consisting of system components (for example AI-Si) and one containing an intermetallic based on components (for example AL-Cu) are proposed. [ABSTRACT FROM AUTHOR]

The effect of heat treatment on the strength of aluminium-titanium bimetal honeycomb structures is considered. Aluminuimtitanium bimetal was produced by vacuum diffusion welding of strips of AD1 aluminium and VT1-0 titanium low alloys. The possibility of spot welding of bimetal strips 12 mm wide for producing the honeycomb core was studied with different combinations of titanium and aluminium layers. It is shown that the optimal method is welding the strips in Al/Ti + Al/Ti combination. Here, the average compressive strength of the honeycomb is equal to 41.1 MPa. Annealing of bimetal honeycombs was performed at temperatures of 600 ºС and 700 ºС. Annealing time at 600 ºС was 60…1200 min., at 700 ºС it was 10…30 min. It is found that annealing for 60 min. at 600 ºС leads to formation of individual sites of an intermetallic interlayer up to 1 ~m thick in the butt joint between the aluminium and titanium layers that that results in increase of compressive strength of the honeycomb samples by 11,7 %, compared to the initial condition. Further increase of annealing time leads to growth of the intermetallic interlayer in the butt joint and to lowering of the compressive strength of the honeycomb samples. It is shown that the honeycomb samples after annealing for 60…600 min at 600 ºС at compression with the maximum deformation level of 50 % deform without fracture of the welding site or bimetal material walls. Increase of annealing time leads to embrittlement of both the welding sites, and the material as a whole. 10 Ref., 2 Tabl., 7 Fig. [ABSTRACT FROM AUTHOR]

Given are the results of investigation of the effectiveness of application of vacuum diffusion welding technology to obtain aluminium-titanium bimetal sheets of 120×120 mm size. The effect of welding parameters on the joint microstructure and mechanical properties was studied. It is established that welding of foil materials is complicated, because of its low deformability. Application of thermally stable SiC and WC powders as «activators» in welding does not allow producing sound joints, because of hard particles embedding into the material being welded, and formation of defects in the form of throughthickness holes. It is shown that application of steel net for activation of plastic deformation on the foil contact surfaces, allows a significant lowering of welding pressure and producing defect-free joints between titanium and aluminium, with 1.7 times higher strength values, compared to layered Al+Ti joints, produced without using the net. [ABSTRACT FROM AUTHOR]

Analysis of publications devoted to producing layered composite materials on aluminium base was performed. The methods of joining thin-foil materials were studied, which allow producing layered joints with different number of intermediate layers. It is shown that the main welding methods, allowing production of joints with a layered structure, are rolling, ultrasonic, explosion, and diffusion welding, and reaction sintering. Analysis of publications showed that the joining process can be conducted, both in vacuum and in air. Joining foil from titanium and aluminium in the welding modes below the aluminium melting temperature (660 °C) allows producing joints without intermetallic phase formation between the layers. In order to improve the strength of the produced composites, it is rational to apply during welding a technological operation in the form of current passing or postweld heat treatment of layered composite materials that provides increase of reactivity between the aluminium and titanium layers and formation of intermetallic phase as the reaction product. [ABSTRACT FROM AUTHOR]

The impact of technological measures in vacuum diffusion welding on formation of the structure and mechanical properties of joints of TiAlNb intermetallic alloy was studied in the work. It is shown that welding of intermetallic alloy by the method of vacuum diffusion welding at temperature Tw = 1050 °C, pressure Pw = 10 MPa, for 20 min does not ensure producing sound joints. After welding, the joint line is visible in the butt, along which there is a considerable number of defects in the form of pore lines. Increase of welding parameters up to the temperature Tw = 1200 C, pressure Pw = 30 MPa, welding time of 30 min, as well as application of a ductile interlayer from NbTi alloy 1 mm thick allows improving the conditions of welded joint formation and greatly reducing the number of defects in the butt joint. During welding, common grains and diffusion zone 25 - 35 ~m thick form between the interlayer material and intermetallic alloy. Application of nanolayered interlayer of Al-Ti system of the total thickness of 25 ~m in welding of TiAlNb intermetallic alloy, combined with cyclic loading in the form of 3 cycles of loading-unloading leads to a change of the nature of the structure in the joint zone. In the microstructures of welded joints obtained by optical metallography, the joint line is not visible. Application of electron microscopy allows detecting in the butt joint a diffusion zone 15 to 20 ~m thick, close by its chemical composition to that of the intermetallic alloy. Investigation of the compressive strength of welded joints demonstrated that the average strength of joints of TiAlNb intermetallic alloy, produced using an interlayer from NbTi alloy, is equal to 988.2 MPa, and application of a nanolayered insert of Al-Ti system in welding allows increasing the average strength of the samples up to 1279.8 MPa. [ABSTRACT FROM AUTHOR]

The impact of scandium in filler wires of SvAMg6, Sv1201 and SvAK5 type, as well as arc oscillations, caused by electric current passage through the filler section, on weld structure formation was studied in nonconsumable electrode argon-arc welding of sheet aluminium alloy D16. Curves of metal hardness distribution in the welding zone are shown and strength limits of welded joints and weld metal after natural ageing of the samples are determined. It is shown that use of scandium filler wires, similar to standard batch-produced ones, leads to formation of a fine-grained dendritic structure of weld metal. However, the subdendritic structure does not form even in welding with arc oscillations, because of a low (0.15 - 0.17%) scandium content in welds. Use of scandium-containing filler wires can lower the degree of weld metal softening at lowering of the total content of the main alloying elements in them. Positive impact of scandium additives together with application of arc oscillations on the degree of softening and ultimate strength of weld metal is noticeable at application of filler wire of Al-Si alloying system. However, the maximum level of strength, both of the welded joints and the weld metal, is ensured in nonconsumable electrode argon-arc welding of D16 alloy 2 mm thick using batch-produced filler wires SvAMg6 and SvMg63. [ABSTRACT FROM AUTHOR]

Effect of structural characteristics and chemical composition of intermediate nanolayers based on Al-Ni system on formation of joints of γ-TiAl based alloy and high-temperature nickel alloy in vacuum diffusion welding was studied. It is shown that application of nanolayered clad interlayers ensures formation of a diffusion zone with monotonic change of the content of components, where the phase composition and micromechanical characteristics are determined by the interlayer chemical composition, as well as lowers the probability of brittle phase formation in the butt joint. [ABSTRACT FROM AUTHOR]

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Three-layer honeycomb panels are widely applied in aircraft construction, ship-building, construction and others industries. In terms of design they consist of honeycomb core and two skins. At relatively small weight, these structures are characterized by high strength values, sound- and heat-insulating properties. The main problem in manufacturing a three-layer structure is welding the upper and lower skins to end faces of the honeycomb core. The work presents the results of development of the technology of manufacturing three-layer honeycomb panels of 150×150 mm size from aluminium alloys. The honeycomb core from AD1 aluminium alloy 0.150 mm thick was produced by joining the corrugated strips into blocks by spot welding. Flatness of end faces of the honeycomb core was achieved by grinding. The structure rigidity was ensured by filling the cells with colophony. Joining of the core to the skins from AMg2 alloy 1.0 mm thick was performed by diffusion welding in vacuum. The process was conducted in a fixture consisting of the lower and upper flanges and bushing. The flanges provided skin pressing to the honeycomb core end faces over the entire contact area, and the bushing allowed homogenizing the temperature in the item and controlling the extent of its deformation during welding. [ABSTRACT FROM AUTHOR]

Three-layer panels with periodic cellular core from aluminium alloys are promising for application in aerospace products, ground and water transportation. The uniqueness of the three-layer panel design consists in that they are characterized by high values of strength and rigidity at a relatively small mass. The work deals with the main types of three-layer panels, design features of manufacturing the cores, methods to join the honeycomb core strips to each other, as well as the three-layer panel elements into one structure. The objective of the presented review is analysis of modern methods of manufacturing three-layer panels from aluminium alloys. Analysis of published data showed that such methods of joining the three-layer panel elements as adhesive bonding and brazing became the most widely applied. Their main disadvantage, however, is increase of the structure mass due to application of an adhesive or braze alloy. Application of diffusion bonding with manufacture of honeycomb core from a stronger titanium alloy for joining three-layer panels or application of a specialized fixture, which allows limiting the degree of plastic deformation of the structure, are promising for welding of three-layer panels. [ABSTRACT FROM AUTHOR]