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The paper investigates the structure and properties of the surface layers of AA5056 and AA2024 aluminum alloy plates 35 to 40 mm thick after reverse-polarity plasma cutting. It is shown that for alloys with varied parameters of the heat capacity, plasma cutting conditions are the same. At the best plasma cutting parameters, the cut geometry shows the lowest distortion. It is found that the cutting surface distortion occurs in exceeding the optimum heat input of the plasma arc. Conversely, at the reduced heat input, the alloy plate cannot be cut to its full thickness. Most of cutting modes provide the higher surface roughness, while the roughness of the upper edge cut reduces relative to the central and lower areas. [ABSTRACT FROM AUTHOR]

The paper focuses on plasma cutting of AA5056 and AA2024 aluminum alloy sheets. It is shown that at the minimum thicknesses, the upper edge of the sheet tends to undercut when using reverse polarity. This phenomenon considerably diminishes when using the best cutting conditions. In the case of the AA2024 alloy, most of the material remains in the cutting zone, adhering to the surface and forming a substantial zone of melting or beading. The AA2024 alloy demonstrates a greater oxidation and hardening of the cutting surface. Degraded material layers and surface roughness reduce when using the best cutting conditions. The upper edge of both alloys is more homogeneous and exhibits less roughness than the lower edge. This is attributed to a more complex displacement of the metal relative to the lower edge undercut. [ABSTRACT FROM AUTHOR]

The effect of heat treatment on the structural evolution, phase transformation, and mechanical strength of Al–12Si obtained using wire electron beam additive manufacturing has been investigated. The as-built Al–12Si alloy was characterized by structural inhomogeneities in the form of interlayer bands with coarsened Si particles resulted from cyclic reheating of the solidified metal. Quenching the as-built samples resulted in the increase of the volume fraction of Al/Si eutectics by 9% with simultaneous refinement of Fe-containing particles. This structure allows obtaining the combination of strength and plasticity better than that of the asbuilt sample. Annealing leads to coarsening of both Si and Fe-containing particles, thereby increasing the Al/Si volume fraction and impairing the mechanical characteristics. [ABSTRACT FROM AUTHOR]

In this work, the characteristics of surface morphology and structure of experimental samples of nickel-based alloy and copper nozzles manufactured by the electron beam additive method have been studied. It is found that the grain boundaries on the outer sample surface are oriented at different angles relative to the substrate due to uneven heat dissipation during printing. It is found that 3D printing in a non-optimal temperature regime produces a highly heterogeneous structure within the material layer. A curvilinear boundary zone is observed in which different structural phase components are formed, including solid solutions and mechanical mixtures. [ABSTRACT FROM AUTHOR]

The present study compares two additive manufacturing methods, wire arc and electron beam ones, by analyzing the structural and mechanical characteristics of 3D printed Ti–Al–Zr–Mo–V alloy components. The macrostructure of the studied Ti–Al–Zr–Mo–V components is represented by columnar primary β grains of the Widmanstatten pattern with lamellar alpha colonies of different sizes and orientation. During the electron beam additive manufacturing (EBAM) process, the concentration of the α-stabilizing Al decreases from 3.81 ± 0.59 to 2.72 ± 0.53 wt.%. However, during the wire arc additive manufacturing (WAAM) process, the Al concentration is kept within the error range. The components printed by the EBAM method show anisotropy of mechanical properties. The ultimate strength is 757–767 MPa for the EBAM-fabricated components and 887– 896 MPa for the WAAM-fabricated components. [ABSTRACT FROM AUTHOR]

The influence of tensile stress on the interface structure of functionally gradient materials is studied in a stainless steel-copper composite fabricated using a wire-feed electron beam technology. A distinct boundary is observed between the two materials, with the two-phase transition regions formed on both sides of the interface. The mechanical tests demonstrate an important role of the interface orientation during the plastic deformation development under uniaxial tensile loading. In the case of the longitudinal and diagonal interfaces, copper and steel simultaneously undergo plastic deformation. The fracture surface also reveals the presence of heterogeneous regions. In the orthogonal interface, necking and subsequent rupture occur in milder copper. However, its mechanical properties are found to be better compared to those of the additively grown copper. [ABSTRACT FROM AUTHOR]

The defect formation and the structure inhomogeneities of composite material samples made from aluminummanganese bronze with various strengthening components added during electron beam printing are studied. The results show a complex and diverse nature of interactions between the components during the electron beam printing of polymetallic systems differing in their structure and composition. The main defects are the pores formed in some cases during optimization of the printing modes. The other defects are the areas of mutually mixed material components formed at the substrate–sample interface, which affect the structure and properties of the resulting products. The components are stirred down to a depth of 10–15 mm from the substrate inwards the sample. The structure and composition inhomogeneities, caused by differing melting temperatures and densities of the components, are most numerous. The formation of these inhomogeneities generally correlates with the material layers deposited on the substrate and does not cause appreciable changes in the mechanical properties of the resulting materials. [ABSTRACT FROM AUTHOR]

The regularities of formation of composite materials from CuAl9Mn2 bronze and 9MnSi5 steel by wire-feed electron beam additive manufacturing are reported. It is shown that an introduction of the strengthening phases of a material with a higher melting point (9MnSi5) into the material with a lower melting point (CuAl9Mn2) results in the formation of strengthening phases with dendritic structure uniformly distributed in the material volume. In the cases where a material with a higher melting point (9MnSi5) is fed into the material with a lower melting point (CuAl9Mn2), an inhomogeneous structure is formed, containing a number of defects of various shapes and sizes. The mechanical properties of the samples of the first type are characterized by an increased strength and plasticity compared to the base metal. The structure of the samples of the second type contains numerous defects, which in some cases sharply deteriorates their mechanical properties. The chemical composition of the sample components and their distributions in the samples vary from layer to layer. [ABSTRACT FROM AUTHOR]

The peculiarities of defect formation in composite materials based on Grade 2 titanium alloy formed by friction stir processing with an addition of pure copper powder particles are studied. The results show that a macroscopically inhomogeneous structure is formed in the samples, which depends both on the number of tool passes along the processing line and on the volume fraction of the powder material added into the stir zone. The main stir zone defects include beading (flash), penetration of substrate fragments, formation of discontinuities and cracks. The stir zone homogeneity can be improved by increasing the number of tool passes along the processing line. However, in the case where the volume fraction of the added powder is large, even a multi-pass mode might fail to achieve a homogeneous stir zone structure. [ABSTRACT FROM AUTHOR]

The features of structure formation and properties of bronze-steel composite samples formed by wire-feed electron beam additive manufacturing are studied. The studies show that at the bronze-to-steel ratio of 1:1 quite homogeneous structure is formed in them, with dendritic steel fragments and bronze filling the interdendritic space. When fabricated at the optimum process parameters, the samples do not contain any pores, inclusions, discontinuities or delamination. The strength characteristics of the resulting composites significantly exceed those of the base pure bronze. The mechanical properties of the samples are very similar in the compression and build direction. The yield strength values, calculated based on the contributions from different phases, differ from the measured values by up to 20%. [ABSTRACT FROM AUTHOR]

The paper deals with friction stir welding of Grade 5 Ti alloy and AA2024 Al alloy sheets based on liquid cooling of welded joints. The metallographic analysis shows the mutual Al and Ti dissolution in the stir zone of the welded joint. The fractographic analysis of the surface shows a non-uniform fracture in the weld zone due to unwelded areas and a brittle fracture due to the presence of intermetallic components, which, in turn embrittle welded joints. By varying the parameters of friction stir welding, the adhesion between the materials is improved to obtain a joint with the highest possible strength. [ABSTRACT FROM AUTHOR]

The results of a study of the surface morphology and structural features of near-surface layers of titanium alloy samples of Grade2 and Ti-2Al-1.5Mn during plasma cutting are presented. The study reveals the formation of martensitic structures with a hardness considerably exceeding that of the base metal in the near-surface volumes of the samples. The Ti-2Al-1.5Mn alloy samples are characterized by relatively low surface oxidation, while the samples of Grade2 alloy are characterized by the formation of oxide layers with a hardness of up to 10–17 GPa. The cut zone structure depends largely on the cutting current and the corresponding values of the heat input. The bottom part of the cut is much less homogeneous than the top part, especially in the cases where the samples are stacked. Cutting with an initially insufficient heat input leads to the formation of beading in the bottom part of the samples or to significant disturbances in the macrogeometry of the cut. [ABSTRACT FROM AUTHOR]

The influence of a plasma jet on pure copper surfaces of different thicknesses is discussed. It is shown that during cutting, due to an intensive removal of molten metal from the cutting zone, a heat affected zone of large thickness and a fusion zone are mainly formed. Plasma cutting of copper sheets, especially those of large thicknesses, is complicated by the dynamic processes of melting, flow and crystallization of the metal displaced from the cavity cut by the gas jet. Inhomogeneities in the metal flow from the cutting zone, a high rate of heat removal and crystallization cause the formation of beading in the lower part of the cut, and its size increases significantly with the thickness of the cut parts. [ABSTRACT FROM AUTHOR]

The structural features of AA2024 and AA5056 aluminum alloy samples under different energy impacts on the material during plasma cutting are studied. The study shows that the influence of the plasma jet impact is ambiguous, since the displacement of the metal from the cutting zone, which also depends on the supply of a shielding or plasma forming gas, plays an important role. The cutting zone is divided into a fusion zone, a heat affected zone, a transition zone and a base metal, which are characterized by different structure and properties. In the bottom part of the sample, at low values of the low heat inputs, beading is formed with a structure similar to that of the fusion zone. The most significant factor is the softening of the AA2024 alloy. The highest values of the macrogeometry distortion of the specimens are characteristic for the AA5056 alloy. [ABSTRACT FROM AUTHOR]

This paper explores the structure and changes in the mechanical properties, chemical composition and surface morphology of aluminum alloys AA5056, AA2024 and Grade 2 titanium alloy after high energy impact during plasma cutting. The studies show that plasma cutting causes the formation of a subsurface layer with a dendritic structure typical of cast material and with a partially altered chemical composition. The subsurface layer material is significantly softened when cutting heat treated alloy AA2024, but changes slightly when cutting AA5056 alloy. During plasma cutting of Grade 2 titanium alloy in shielding atmosphere, the presence of even a small amount of atmospheric oxygen leads to the formation of oxides in the layer closest to the surface, which have microhardness values more than 5–7 times higher than the base metal hardness. Below the surface layer with a molten structure, a heat-affected zone is formed where the structure of the base metal is changed as a result of thermal influence. Significant changes in this zone are characteristic only for heat treated alloy AA2024. Metal flow in the cutting zone initiated by the plasma jet and shielding gas flow occurs in both the laminar and vortex modes. Nonuniform metal flow in the cutting zone and nonoptimal process parameters lead to the formation of structural heterogeneities and defects of different structural and scale levels on the surface of the samples. [ABSTRACT FROM AUTHOR]

An effect of friction forces on the structure and composition of the near-surface layer of an Al–13Sn–5Fe (at %) composite containing a large amount of agglomerates of FeAl3 particles cemented with tin was studied. The investigated composite was prepared by sintering a mixture of Al, Sn, and Fe elemental powders in vacuum for 1 h at a temperature of 620°C and subsequent compaction in a closed die at a pressure of about 300 MPa and a temperature of 250°C. The counterbody was made of heat-resistant X40CrMoV5-1 steel and was a truncated steel cone with a helical surface. The speed of material points lying on the outer perimeter of the section of the rotating cone pressed against the composite was 0.36 and 0.54 m/s. The normal pressure on the end surface of the composite specimen was 16 and 32 MPa with a load on the cone of 150 and 300 kg, respectively. It was found that three layers are formed under the friction surface, which differ in the value of the accumulated deformation. The closer to the friction surface the layer is located, the narrower it is. The uppermost layer consists of highly crushed iron aluminide particles mixed with ultrafine tin and aluminum particles. It also contains a lot of oxygen in the form of fragments of oxide films, which is why it has a high microhardness, reaching 2000 MPa or more. The thickness of this layer increases with increasing processing pressure and reaches several hundred micrometers. Based on the results of the study, it is concluded that pretreatment of the surface of aluminum matrix composites by smoothing with a flat steel counterbody leads to its charging. This fact will increase its wear resistance, however, the optimal mode of such processing and the shape of the processing tool require additional research. [ABSTRACT FROM AUTHOR]

Electron beam additive manufacturing with simultaneous feeding of two dissimilar metal wires was used to obtain Ti-6Al-4V specimens successively alloyed with 0.6, 1.6, 6.0 and 9.7 wt % Cu. The specimens were characterized for microstructure, phases, and mechanical properties. Increasing the copper content in the alloy from 0.6 to 9.7 wt % resulted in the refinement of primary β-Ti grains and the columnar-to-equiaxed grain transformation owing to the effect of constitutional undercooling on grain nucleation and growth. The grain growth restriction factor was calculated to substantiate the microstructural evolution from columnar to equiaxed grains. Admixing with up to 6.0 wt % Cu resulted in the formation of ultrathin α-Ti platelets, while increasing the copper content to 9.7 wt % Cu led not only to further thinning of α-Ti platelets but also to the formation of refined α′-Ti and α″-Ti phases. Intermetallic Ti2Cu particles were precipitated due to the β → Ti2Cu + α eutectoid decomposition of primary β-Ti grains and then plausibly induced heterogeneous nucleation of α-Ti platelets. A combined effect of solid solution hardening, precipitation hardening, and grain boundary hardening was achieved and allowed increasing the microhardness, ultimate tensile stress, tensile yield stress, and compression yield stress of Ti-6Al-4V/Сu specimens. [ABSTRACT FROM AUTHOR]

Abstract—The subsurface macrostructure of a sintered Al–7Fe–38Sn composite material, which forms during the rotation of a flat steel bar pressed against it, is investigated. A zone of intense plastic flow is found to form under the friction surface of the composite material due to thermal softening. The zone size and the degree of refinement of structural elements in it increase as the applied pressure and the sliding velocity increase. The plastic flow zone thickness is ≈200 μm at a pressure of 15 MPa and increases with the pressure. A thin layer with a homogeneous ultrafine-grained structure forms between the friction surface and the plastic flow zone. [ABSTRACT FROM AUTHOR]

In the present work, two types of composite materials obtained using electron beam additive manufacturing of aluminum bronze and mixtures of Fe–Ni and Fe–W powders have been studied. Methods of metallographic analysis show relatively uniform distribution of strengthening phases in the volume of products with the presence of only a small number of agglomerates. Mechanical properties of samples are at a sufficiently high level compared to the properties of pure bronze CuAl9Mn2. Microhardness of the surface layers of composites increase up to a factor of 1.5 in comparison with the raw metal. Tribological properties in a set of parameters of mass and linear wear are higher at the composite material with addition of Fe–W powder mixture. Friction coefficient of composite samples of both types is at the same level. [ABSTRACT FROM AUTHOR]

The paper studies the influence of wire-arc additive manufacturing process parameters of aluminum– manganese bronze CuAl9Mn2 products on the structure and mechanical properties of samples The microstructure of aluminum bronze is defined by the presence of α-Cu(Al) solid solution and residual martensitic β-phase of Cu3Al. Insignificant anisotropy of mechanical properties of the samples cut in sections parallel and perpendicular to the direction of printing has been revealed. Samples cut in the cross section parallel to the printing direction show the highest values of the tensile strength and less ductility compared to the samples cut in cross section perpendicular to the printing direction. The tensile strength values vary from 515 MPa to 591 MPa between blades cut along and across the ply application. The strength of the hot-rolled product (440 MPa) is 25% lower than the strength of the product obtained by the WAAM method (591 MPa). It is shown that a change in the heat input does not affect the average width of the dendritic grains in the cross section perpendicular to the printing direction. It was found that changing the printing mode can lead both to an increase in the mechanical properties of the samples and to violations of the geometry of the obtained samples. [ABSTRACT FROM AUTHOR]

In the present work, mechanical and tribological investigations of samples based on Cu–Fe system with different amounts of austenitic steel in the copper matrix have been carried out. By the method of electron-beam wire additive technology, samples of metal matrix composites have been obtained from heterogeneous materials with introduction at printing of 10, 25, 36 and 50% of steel 321 in the matrix of copper C11000. In the work, essential orientation dependence of mechanical and tribological behavior of samples is established. For samples the friction plane of which was located longitudinal to layers, fast growth of wear intensity at increase in the content of copper has been revealed. It occurs due to the lesser role of friction adhesion and plastic displacement of the sample material from the friction contact zone. It is revealed that at increase of the volume fraction of steel introduced into the copper matrix, there is a limit in hardening of composite material. At introduction of more than 25% of steel, the mechanical properties of the material change sufficiently weakly. Changes of the mechanical properties of materials at increase of the steel content up to 50% consist in essential growth of plasticity. At tribological tests, the essential decrease in average coefficient of friction and wear is revealed at samples with steel content of 50%, the friction plane of which has been located transvese to the applied layers. For all samples, the wear resistance was higher than that of additive samples of pure copper. [ABSTRACT FROM AUTHOR]

The regularities of structure formation and operational properties of bimetallic functionally graded samples made of nickel-based Udimet500 and bronze CuCr1 have been investigated. The results of obtaining samples with different order of deposited layers on the substrate were obtained. It was found that deposition of nickelbased superalloy on copper alloy forms a gradient zone of less thickness than deposition of copper alloy on nickel-based superalloy. The structure of the transition zone is characterized by a division into a region of mechanical mixing of the components and a region with a smoothly changing composition, extending to the pure alloy. The extended smooth gradient zone is characteristic of the component deposited in the top part of the sample, and the boundary with the component located in the bottom part is sharp. The mechanical properties of the gradient zone of the samples are at the level of the least strong component, bronze CuCr1. Tensile rupture of the samples occurs along the bronze area. [ABSTRACT FROM AUTHOR]

The paper considers the change in mechanical and tribological properties of rolled sheets of aluminum bronze CuAl9Mn2 with addition of 10% tungsten powder after multipass friction stir processing. The defect-free structure has been achieved after the third pass. The grain size decreases with every subsequent pass, except for the fourth one, after which an insignificant increase in the grain size was detected. It is shown that the samples with 10% W has the best values of the ultimate tensile strength (616 MPa) for four tool passes, with a 23% increase in the strength value relative to the base material. Dry sliding friction tests show that the material friction coefficient in the stir zone increases when W is added by friction stir processing. However, due to the improved mechanical properties, the sample mass loss and the wear rate after four passes are significantly decreased. [ABSTRACT FROM AUTHOR]

Permanent joints are successfully formed by butt friction stir welding of rolled sheets made of Ti-6Al-4V titanium alloy, using a tool made of a heat-resistant alloy based on nickel ZhS6U with liquid cooling in the welding process. It is revealed by the methods of metallographic analysis that the fragments of the welding tool material in the stirring zone get dissolved. A fractographic analysis of the fracture surfaces demonstrates that the fracture in the joint zone is ductile, while in the areas with the tool material fragments it is brittle. By varying the friction stir welding parameters a permanent joint is formed, whose strength competes with that of the base metal. [ABSTRACT FROM AUTHOR]

Microstructure and mechanical characteristics of aluminum bronze fabricated using electron beam additive manufacturing (EBAM) under adjusting the heat input as a function of the sample's height are investigated. It is shown that this adjustment has an effect on the dendrite grain size, morphology and mechanical characteristics. Columnar high aspect ratio grains are formed during deposition at the maximum heat input values. The columnar grain width in the section parallel to the deposition direction is increasing in the EBAM conducted at a lower heat input. The tensile static tests show that the tensile strength values are improving from 435 to 483 MPa. A moderate degree of anisotropy is revealed between the samples oriented by their tensile axes parallel and perpendicular to the deposition direction. The samples with tensile axes parallel to the deposition direction show higher tensile strength and lower plasticity than those of the samples with perpendicular orientations of their tensile axes. Furthermore, the heat input adjustment has no effect on the mean width of the columnar grains measured in a section perpendicular to the deposition direction. [ABSTRACT FROM AUTHOR]

The results of model experimental studies of structural-phase changes in an AA2024 aluminum alloy after friction with a counter-body of a complex configuration are presented. The peculiarities of formation of the transfer layer structure in the material after friction stir processing and after frictional interaction, followed by the material extrusion from the friction zone, are revealed. The experiments show that the structure formed during frictional interaction significantly varies in different areas depending on the distance to the counter-body. After the frictional contact, accompanied by the material extrusion from the contact zone, a structure of a solid solution based on aluminum and secondary phase particles is formed, whose grain size is similar to that formed after friction stir welding. The main differences between the structures formed by the friction stir processing and intensive frictional interaction consist in the morphology and distribution of the secondary-phase particles. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) is an advanced technology of surface modification of microstructure of metals and alloys in order to improve mechanical and operational properties. Previous works on processing of titanium alloys demonstrated that variation of FSP process variables (such аnticlockwise rotation rate, processing speed and plunge force) significantly influences on evolution of microstructure and mechanical properties of Ti6Al4V alloy. However, the influence of multipass FSP on Ti6Al4V alloy has not been studied. Thus, this work studied the influence of four-pass FSP of Ti6Al4V titanium alloy on evolution of microstructure and mechanical properties of this alloy. Analysis of the microstructure has demonstrated that, in the stir zone, a heterogeneous microstructure is formed with dynamically recrystallized equiaxial α and β grains and β regions with α phase of acicular and laminar types, which is related to the temperature gradient of the stir zone during FSP. It has been established that, with increase in the number of FSP passes to three, there is an increase in ultimate strength (up to 1173 MPa) and wear resistance (by 33%). Improvement of the ultimate strength after three passes of FSP is dictated by a decrease in grain size in the stir zone by 88% in comparison with the initial Ti6Al4V alloy. It has been demonstrated that, after four passes of FSP in the stir zone, an increase in the gain size and a decrease in the ultimate strength to 686 MPa occur, which is related to formation of coarse defects along the contours of metal flows. At the same time, the wear resistance of Ti6Al4V alloy after four passes of FSP increases by 39% in comparison with the initial material. [ABSTRACT FROM AUTHOR]

This article is the first to apply wire-feed electron beam additive manufacturing in vacuum to fabricate a part from a complex nickel-based superalloy with directional structure on a stainless steel substrate. It is shown that the determining factor for the formation of parts with directional structure is the local metallurgy conditions implemented in electron beam additive manufacturing. These conditions are the magnitude and direction of the temperature gradient as well as the geometry (shape) of the solidification front in the molten pool. The substrate effect (both chemical and structural) on the composition and structure of the part material is cancelled out at a distance not exceeding 8.0 mm from the substrate. Thus, the proposed 3D printing method is quite acceptable for the manufacturing of parts from heat-resistant nickel alloys with directional structure on substrates made of less expensive materials. [ABSTRACT FROM AUTHOR]

The structure of samples of the C27400 copper alloy coatings on the AA5056 aluminum alloy surface, produced by friction stir processing of a rolled sheet package is studied. The regularities of the structure formation at deformation-initiated mixing of Al–(Cu, Zn) system components are elucidated. Intensive diffusion and mechanical mixing of the Al–(Cu, Zn) system components is revealed, resulting in the formation of a complex structure of the stir zone on the macrolevel. It is established that during the formation of the structural-phase composition of the coating, the solid aluminum solutions are formed in copper by zinc extrusion from the solid solution together with complex solid solutions and intermetallic phases by zinc diffusion into the aluminum lattice. [ABSTRACT FROM AUTHOR]

The paper studies Ti-6Al-4V alloy specimens obtained by wire-based electron-beam additive manufacturing (EBAM) and characterized by the structure with a defective region produced by uncontrolled wire fluctuations during 3D printing. Metallographic analysis and tensile strength tests and microhardness measurements are conducted to determine the defect influence on the structure and properties of the alloy. It is shown that the defective region represents the primary β-phase grains that are finer than those of the EBAM specimens commonly exhibiting a columnar structure. The specimen microhardness both in the defective and defect-free regions, is identical. The deformation behavior of the alloy is mostly subject to the influence of such defects, since the plasticity and ultimate tensile strength of the defective region are respectively higher and lower than that of the defect-free region. [ABSTRACT FROM AUTHOR]

This paper describes the results of an investigation into a microstructure formation on a wire-feed electron beam additive manufactured "steel–copper" bimetallic sample. The peculiarities of a gradient zone structure with a smooth change of components' concentration are revealed. The heterogeneity of copper and steel distribution in the gradient zone is provided by copper solidification and precipitation mechanisms. Both solidification of coarse copper inclusions in the interdendrite areas or along the dendrite boundaries and precipitation of fine Cu-based particles at the cooling stage from the solid solution of Cu in γ-Fe are the main factors of structure formation during the double wire gradient zone deposition. The presence of such fine copper precipitates from the supersaturated solid solution was revealed by means of transmission electron microscopy. The shape of copper particles in the gradient zone varies from spherical to oblong and irregular. The shape of steel particles and/or grains is mainly determined by the peculiarities of the crystallization zone and is characterized by the primary crystallization of γ-iron dendrites from the liquid melt. A physical scheme describing a variation in phase composition and microstructure in gradient zone of the bimetallic specimen was proposed. [ABSTRACT FROM AUTHOR]

Electron beam wire-feed additive manufacturing is given less attention in research community compared with other additive manufacturing methods, despite it allows higher deposition rate and less porosity. However, both gas and shrinking porosity are still met even with this method especially if applied to light alloys. The excess heat input may be the reason for evaporation of volatile metals, and forming the gas pores especially in the top layers of the built sample where cooling rate is reduced. Therefore, exponential decay heat input was used to grow AA5356 samples. Microstructural and mechanical characterization of the samples obtained at mean low, medium, and high heat input levels was carried out. An optimal heat input gradient was determined which allowed growing a defect-free metal in the bottom part of the sample and forcing out the shrinkage cavities to the top part. Shrinkage and gas pore structure formation was analyzed as a function of the heat input gradient and along the building direction. Gas pores resulted at two higher heat input regimes as a result of evaporation of magnesium as supported by the results of EDS and XRD. Tensile test showed the ultimate strength of the defect-free part equal to that of the base AA5356. [ABSTRACT FROM AUTHOR]

The paper considers the physical and mechanical properties of bimetallic tungsten-copper powders after explosive compaction. This method is used to produce rather dense powder compacts from tungsten-copper nanoparticles. The structural analysis and the analysis of physical and mechanical properties of the obtained composites show that the pressure reduction and an increase in the time of explosive compaction considerably improve the composite hardness and mechanical properties. [ABSTRACT FROM AUTHOR]

Samples of AA5356 aluminum alloy manufactured by the electron-beam additive method and modified using the friction stir processing method have been investigated. Processing was carried out along and across the sample growth direction. It has been established that pores formed in the 3D-printing process are eliminated during friction stir processing by the severe thermo-mechanical action. It has been found that the modes are not the same for different processing directions. As a result of adjustment of the processing parameters, it has been revealed that a higher loading force must be applied to form a high-strength stir zone across the direction of layers deposition. This is caused by the interlayer boundaries that were formed during layer deposition process and offered greater mechanical resistance to the tool. [ABSTRACT FROM AUTHOR]

The paper is devoted to studying two different ways of obtaining the complex-shaped bell-type samples from the titanium alloy Ti-6Al-4V. It is shown that the process of obtaining the samples on a three-axis table is sensitive to the wire feed geometry as depended on four such geometry zones. These zones are characterized by the angles between the wire feed direction and the tangent to the printing path. On the contrary, samples obtained on a rotary four-axis table are not sensitive to the wire feed geometry. Each of the two ways provides formation of its own specific types of the structure and different mechanical characteristics. In this paper, the structure of geometry affected zones is determined and the most optimal way for obtaining the samples is selected. [ABSTRACT FROM AUTHOR]

Multipass friction stir processing was applied to AA2024 8-mm-thick samples with the goal of studying the microstructural evolution of the metal processed. Up to three parallel FSP tracks with an overlap of 0.375 between the neighboring ones have been obtained on the samples and then characterized for microstructure and mechanical strength. Clear macroscopic zones between the tracks have been observed. The specificity of microstructural evolution in the fine crystalline part of the thermo-mechanically affected zone formed close to the stirring zone is its over-aging due to less intensive strain dissolution of precipitates as compared with that of the stirring zone. The minimum hardness zone is formed there while higher hardness is observed in the less deformed part of the zone due to S(S′) (Al2CuMg) precipitates. The thermo-mechanically affected zone formation was considered from the viewpoint of tribology when the stirring zone metal flow slides over the thermo-mechanically affected zone metal and deforms it. [ABSTRACT FROM AUTHOR]