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In this work, Ce0.9Gd0.1O1.95 (10GDC) powders were synthesized by thermal decomposition of oxalate precursor crystals Ce1.8Gd0.2(C2O4)3·10H2O having a plate shape. The morphology of the oxide was found to be strongly influenced by the dehydration conditions of the precursor crystals. Dehydration in air at 125 °C led to the formation of the product in a pseudomorph form, retaining the shape of the precursor crystals and showing only slight dimensional changes. The formation of a pseudomorph was accompanied by a loss of crystallinity. When dehydration occurred at an increased water vapor pressure at the same temperature, a crystalline product formed having a significantly altered morphology. Unlike dehydration in air, after which the crystals retained their shape, an intensive shattering of the crystals occurred upon dehydration at an increased water vapor pressure. Structural transformations during dehydration were shown to determine the product morphology. The 10GDC powders with different textural characteristics were obtained by oxidative thermolysis (at 300 °C) of dehydration products. The oxide powders were sintered by spark plasma sintering at a temperature of 1100 °C and a pressure of 40 MPa. The microstructure, relative densities, and conductivities of the ceramic samples obtained from powders of two different morphologies were compared. The sintered ceramic samples had comparable grain size (

At present, metallic glasses are evaluated as alternative reinforcements for aluminum matrix composites. These composites are produced by powder metallurgy via consolidation of metallic glass-aluminum powder mixtures. In most studies, the goal has been to preserve the glassy state of the reinforcement during consolidation. However, it is also of interest to track the structure evolution of these composites when partial interaction between the matrix and the metallic glass is allowed during sintering of the mixtures. The present work was aimed to study the microstructure and mechanical properties of composites obtained by spark plasma sintering (SPS) of Al-20 vol.% Fe66Cr10Nb5B19 metallic glass mixtures and compare the materials, in which no significant interaction between the matrix and the Fe-based alloy occurred, with those featuring reaction product layers of different thicknesses. Composite materials were consolidated by SPS at 540 and 570 °C. The microstructure and mechanical properties of composites obtained by SPS and SPS followed by forging, composites with layers of interfacial reaction products of different thicknesses, and metallic glass-free sintered aluminum were comparatively analyzed to conclude on the influence of the microstructural features of the composites on their strength.

Copper-graphite joints are functional elements of many electronic and electromechanical devices. Unique properties of graphite, such as the ability to withstand high temperatures, a low friction coefficient and high thermal and electrical conductivities make it an attractive material for various applications. For enabling efficient heat sink or making sliding electrical contacts, graphite requires joining to metallic copper. Poor wettability between copper and graphite is a problem that needs to be overcome to form a reliable joint. In the present work, we used a Ti25Cu75 alloy to braze graphite to copper in a pulsed current-assisted process. Brazing was carried out in a Spark Plasma Sintering (SPS) apparatus under a uniaxial pressure of 13 MPa. The SPS conditions – a possibility of localized heating under an applied pressure in dynamic vacuum – are beneficial for the joining processes of conductive materials. For joining graphite and copper plates, a die-free configuration was used. The microstructure and the phase composition of the copper-graphite brazed joints were investigated. Strong joints were formed when the upper electrode temperature measured by a thermocouple reached 700 °C. At the graphite-alloy interface, a TiC layer 0.5–1 μm thick was formed; in addition, TiC particles were found in the metallic matrix in a layer 5–10 μm thick adjacent to the graphite plate. The tensile strength of the brazed joint was higher than the tensile strength of graphite (13 MPa).

The effect of boron additives on the corrosion resistance of Ni3Al intermetallic obtained by spark plasma sintering of powder mixtures with preliminary mechanical activation in alkali water is studied. It is established that monophasic nickel aluminide and alloyed with 0.1% B has high corrosion resistance in boiling solutions of strong alkalis, such as potassium and sodium hydrate. The corrosion rate in such medium is less than 0.05 mm/year, even when corrosion activators are added into the solution. High corrosion resistance is due to the processes of passivation of the material during the interaction of the surface of the material with the solution. Solutions of weak alkalis have a more aggressive effect on sintered nickel aluminide. It is shown that the corrosion rate of intermetallic in aqueous ammonia is 0.22…0.24 mm/year. With the boron addition, the corrosion rate increased to 0.29 mm/year.

Bimetals produced by explosion welding of titanium alloy VT23 and steel 45KhNM through an intermediate layer of steel 08ps followed by a heat treatment consisting of quenching and tempering are studied. The three-layer composite is subjected to metallographic analysis prior to and after the heat treatment with the help of an optical microscope and a scanning electron microscope equipped with an energy dispersive analyzer. The chemical composition and the hardness of the welded materials and of various regions of the weld are determined, and the changes in these parameters after the quenching and tempering are assessed.

Silver oxalate Ag2C2O4 is an interesting compound from both fundamental and practical viewpoints. Decomposition of Ag2C2O4 results in the formation of metallic silver, whose size and morphology can be tailored for different applications. In this work, we focused on the morphological features of silver that forms upon decomposition of Ag2C2O4 in a spark plasma sintering (SPS) apparatus. While crystals heated in a conventional furnace decompose to produce silver in the form of a pseudomorph, decomposition induced by heating in a SPS chamber at a rate of 30 °C·min-1 via a pressureless process results in the formation of foam-like porous silver. Decomposition of Ag2C2O4 was also carried out under pressure by placing the powder between copper plates and heating the assembly in a SPS die. A feasibility study has shown that Ag2C2O4 powders can be used for joining copper plates in a fast process enabled by the SPS method. Joints formed by the SPS method at 300°C and 13 MPa were formed by silver with 500-nm crystallites; the shear strength of the joints was 45 MPa.

The paper is devoted to the study of the structure and properties of the Ni3Al intermetallic obtained by spark plasma sintering and modified with 0.2 wt.% of boron. It is shown that, in the structure of the material, in addition to the Ni3Al intermetallic, there are regions represented by a mechanical mixture. The mechanical mixture is characterized by cube-shaped nickel aluminide particles surrounded by a matrix of solid aluminum solution in nickel. These regions have a coarser morphology and are better manifested on intermetallic samples modified with boron than in similar samples without additional alloying elements. It is shown that the boron microaddition positively affects the strength and toughness of the synthesized materials. The ultimate strength increases from 400 to 720 MPa; impact strength increases from 5.3 to 14.2 J/cm2.

Features of the structure of a layered material welded by explosion of high-strength titanium alloy and tool roller steel with an intermediate layer of the structural low-carbon steel have been studied. The structural transformations occurring in materials upon their dynamic interaction have been analyzed. Particular attention is paid to the structure of vortex zones formed at the interfaces of billets of various steels, as well as structural steel and titanium-based alloy. The structural analysis methods made it possible to fix stable and metastable joints appearing upon the explosive welding of various metals. To reveal features of structural transformations caused by prolonged heating, billets of titanium alloy and structural steel were also joined by diffusion welding. It has been shown that, in the course of the diffusion welding process, a continuous layer of stable brittle intermetallic compounds is formed along the entire interface of the welded materials. In the explosively welded materials, the intermetallic phases are distributed locally and, thus, they have a weaker embrittlement effect.

In this article, the features of the in-situ synthesis, microstructure evolution and mechanical properties of TiC-Cu composites obtained by mechanical milling and spark plasma sintering (SPS) are presented. The goal of this work is to study the effect of the carbon source on the microstructure evolution during the manufacturing of TiC-Cu composites from Ti-C-3Cu mixtures. Graphite, nanodiamonds and carbon black powders are compared as the carbon sources in the synthesis in terms of their influence on the structural evolution of the composite mixtures. In the case of graphite, mixing and alloying are retarded at the initial stages of milling. The use of carbon black and nanodiamonds ensures faster conversion of the reactants into the products during milling compared with graphite, as concluded from the studies of thermal explosion of those mixtures. Irrespective of the source of carbon, melting is observed at the contacts between equiaxed particles in the materials consolidated by SPS leading to the formation of composites with an interesting (unconventional) microstructure. The compressive yield strength, ultimate compressive strength and hardness of selected TiC-Cu composites are reported. A TiC-Cu composite with an attractive combination of properties has been obtained (processing conditions: Ti-Cgraphite-3Cu mixture, 10 min of milling, SPS at 980°C): a relative density of 95%, a compressive yield strength of 820 MPa, an ultimate compressive strength of 920 MPa, a hardness of 360 HV, a deformation at fracture of 2%, and an electrical conductivity of 18% of the International Annealed Copper Standard.

A Fe-40 at.%Al loosely packed powder mixture was subjected to pressureless treatment in a vacuum chamber of a Spark Plasma Sintering facility and sintered in a hot press in an argon atmosphere with and without applying mechanical pressure. The treatment conditions were varied to determine whether the electric current and the heating rate play any roles in the formation of FeAl compacts with a high open porosity (41–51%). Rapid heating of a loosely packed Fe-Al mixture in the SPS chamber with or without an electric current passing directly through the sample ensures a fast transformation of the reaction mixture into a highly porous FeAl product, the passage of electric current through the sample not being responsible for the preservation of high open porosities. The transverse rupture strength of porous FeAl did not depend on the sintering method for compacts of the same total porosity, but increased when the total porosity decreased.

Ti/Ni alloy-based laminate composite materials were produced by explosive welding with two thin intermediate layers of tantalum and copper placed between Ti and Ni alloy layers. The influence of the thickness of the Cu interlayer (0.1–0.7 mm) on the structure and mechanical properties of the explosively welded composites was examined. Investigations carried out by optical and scanning electron microscopy showed the formation of an inhomogeneous structure in the vicinity of the interfaces with zones of local melting and cavities within these zones. The wavelength and the amplitude at the interface between the copper and tantalum interlayers changed with the thickness of the copper layer. In order to evaluate the mechanical properties of the composites containing copper interlayers of different thicknesses, microhardness, tensile, and bending tests were performed. As the thickness of the copper layer was decreased to 0.3 mm, the tensile and bending strengths of the laminate composites increased.

In the present study, a mixture of powders (87.9 at.% Ni, 12 at.% Al, 0.1 at.% B) was used as the initial material to produce sintered Ni3Al + B alloy. Spark Plasma Sintering (SPS) method was used to compact the powder. The powder mixtures were previously prepared in two ways: mixing the initial powders in a mortar (М1) and mechanical activation (М2). The microstructure was observed using optical microscope (OM). The addition of small amount of boron to the initial mixture of nickel and aluminum improves the density of the sintered Ni3Al intermetallic compound (98.8%). The results of density, bending and microhardness tests showed, that the provisional three-minute mechanical activation improves almost all properties of the sintered material. The compact obtained by SPS by M2 contributes to the formation of a homogeneous fine-grained structure of the material. It leads to further increase in flexural bending strength up to 2200 MPa. This value is almost 8 times the strength of the intermetallic Ni3Al stoichiometric composition obtained by SPS.

In this article, structural and mechanical characterization of porous iron aluminide FeAl with a high open porosity obtained by one-step fast synthesis is presented. FeAl compacts produced by pressureless Spark Plasma Sintering of the Fe-40at%Al powder mixtures at 800 and 900 °C for 3 min had open porosities of 41% and 46%, respectively. An important result of this work is high values of the open porosity of the synthesized FeAl achieved without any pore forming additives by inducing a rapid chemical reaction between iron and aluminum in an electric current-assisted sintering process. Transverse rupture strength (TRS) of the porous FeAl was determined from the experiments on indentation of a steel ball into the disk-shaped sintered specimens. Finite element modeling of the specimen rupture during indentation was carried out in ANSYS 17.0 software. The TRS values of the FeAl compacts obtained analytically were close to those obtained numerically. The TRS of the porous FeAl sintered at 700–900 °C ranged between 53 and 72 MPa and did not change significantly with the sintering temperature.

In this work, Ti25Cu75 melt-spun partially amorphous alloy was used as a source of Ti and Cu to synthesize in-situ TiC-Cu nanocomposites. The reaction between the alloy and carbon started during ball milling and continued during Spark Plasma Sintering. At the same time, during ball milling, the alloy experienced phase transformations: crystallization of the amorphous phase was followed by decomposition of TiCu3. Copper crystallites formed during the alloy transformations were the reason for the presence of copper regions 0.5–1 µm in size free from TiC nanoparticles in the sintered composites. The Ti-Cu intermetallics transformed into non-agglomerated TiC 10–20 nm in size distributed in the copper matrix. The hardness of the synthesized TiC-Cu nanocomposites exceeded that of composites obtained by conventional sintering of ball-milled Ti-C-Cu powders.

In this paper, the structural characteristics of a W-Ta-Mo-Nb-V-Cr-Zr-Ti non-equiatomic refractory metal alloy obtained by spark plasma sintering (SPS) of a high-energy ball-milled powder mixture are reported. High-energy ball milling resulted in the formation of particle agglomerates ranging from several tens to several hundreds of micrometers. These agglomerates were composed of micrometer and submicrometer particles. It was found that, during ball milling, a solid solution of A2 structure formed. The grains of the sintered material ranged from fractions of a micrometer to several micrometers. During SPS, the phase transformations in the alloy led to the formation of a Laves phase of C15 structure and ZrO and ZrO2 nanoparticles. The microhardness of the ball-milled alloy and sintered material was found to be 9.28 GPa &plusmn, 1.31 GPa and 8.95 GPa &plusmn, 0.42 GPa, respectively. The influence of the processing conditions on the structure, phase composition, and microhardness of the alloy is discussed.

Titanium carbide (TiC), is the most thermodynamically stable compound in the Ti−C−Cu system, which makes it a suitable reinforcement phase for copper matrix composites. In this work, the interaction of a Ti−Cu alloy with different forms of carbon was investigated to trace the structural evolution leading to the formation of in-situ TiC−Cu composite structures. The reaction mixtures were prepared from Ti25Cu75 alloy ribbons and carbon black or nanodiamonds to test the possibilities of obtaining fine particles of TiC using ball milling and Spark Plasma Sintering (SPS). It was found that the behavior of the reaction mixtures during ball milling depends on the nature of the carbon source. Model experiments were conducted to observe the outcomes of the diffusion processes at the alloy/carbon interface. It was found that titanium atoms diffuse to the alloy/graphite interface and react with carbon forming a titanium carbide layer, but carbon does not diffuse into the alloy. The diffusion experiments as well as the synthesis by ball milling and SPS indicated that the distribution of TiC particles in the composite structures obtained via reactive solid-state processing of Ti25Cu75+C follows the distribution of carbon particles in the reaction mixtures. This justifies the use of carbon sources that have fine particles to prepare the reaction mixtures as well as efficient dispersion of the carbon component in the alloy−carbon mixture when the goal is to synthesize fine particles of TiC in the copper matrix.

In this study, forty-layered Ti-Al composites were fabricated in a single-shot explosive welding process. The structure of the composites was thoroughly investigated using scanning and transmission electron microscopy. Particular attention was paid to the structure of the mixing zones (vortexes) arising at the interfaces during explosive welding. The complicated process of mixing and rapid solidification of these zones led to formation of different stable and metastable structures. The vitrification of vortexes, formation of “disordered” Ti3Al and ordered solid solution of Al in hexagonal-Ti and Ti in FCC-Al were observed and discussed with respect to the conditions of solidification. Subsequent heat treatment was carried out at 640 °C under atmospheric and at 3 MPa pressure. For comparison, there were produced reference samples by reaction sintering at the same conditions as for the heat treatment. The heat treatment and reaction sintering promoted the formation of stable Al3Ti phase between Ti and Al. It was found that preliminary explosive welding accelerated the formation of Al3Ti layer and made heat treatment duration four times shorter. The application of pressure was found to play an important role at the final stage of heat treatment after explosion welding to avoid formation of defects between the plates. Keywords: Explosive welding, Multilayer, Titanium, Aluminum, Intermetallic, Composite

In this work, tungsten- and molybdenum-containing coatings on diamond were obtained by rotary chemical vapor deposition (RCVD) or by treating the diamond microcrystals in a hot press (HP)/spark plasma sintering (SPS) facility. In the HP facility, heating was realized by external heating elements; no electric current was passing through or induced in the die. In RCVD, tungsten carbonyl W(CO)6 was used as a precursor. In the case of HP and SPS, powders of tungsten, molybdenum and tungsten trioxide WO3 were used as sources of the metal. It was found that the morphology and phase composition of the coatings depend on the deposition conditions and the metal source. HP and SPS were further used for fabricating bulk copper–50 vol% diamond composites. The thermal conductivity of the copper–diamond composites decreased as the holding time during their consolidation by HP or SPS increased owing to delamination of the WC coating from the diamond surface. A Mo-containing coating deposited by the SPS treatment allowed obtaining a copper–diamond composite with a thermal conductivity of 420 W m−1 K−1.

An experimental study of the effect of thermal conditions and some technological methods (intermediate inserts made of monolithic metal, nano-modifying additives) on the quality of the permanent joint of porous titanium obtained by laser welding was carried out. It has been established that to obtain a high-quality defect-free weld it is necessary to use an intermediate insert made of compact metal, butt-mounted between the ends of the plates to be welded. In this case, the position of the focal spot should be set at a depth equal to the thickness of the plate, i.e. on its bottom surface. The use of modifying additives based on titanium nitride increases the dispersion and homogeneity of structure of the weld and neighboring area, which, according to the Hall-Petch law, has a positive effect on the mechanical characteristics of the metal.

In this work we perform an investigation of the influence of duration of preliminary mechanical activation in high energy ball mills on the microhardness of Ni3A intermetallide specimens synthesized under conditions of spark plasma sintering.

One of the ways to simultaneously increase the strength and the fracture and impact toughness of structural materials is by producing multilayered materials. In this paper we discuss the structure and properties of a seven-layer composite obtained by explosive welding of high-strength titanium alloys. The structure of the composite was characterized using light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). At the interfaces between plates, formation of waves and vortices was observed. The wave formation is discussed with respect to the kinetic energy loss. The vortices consisted of a mixture of two alloys and possessed a martensitic structure comprising &alpha, &prime, and &beta, phases of titanium. Localized plastic deformation occurred along the interfaces during explosive welding by formation of shear bands. The most intensive shear banding occurred in the vicinity of the upper interfaces. The local hardness at the interfaces increased due to the formation of the quenched structures. The interfaces between titanium alloys positively influenced the impact toughness of the composite, which increased in comparison with that of bulk titanium alloys by a factor of 3.5. The strength characteristics of the composite remained at the same level as that of the bulk material (1100&ndash, 1200 MPa).

Pulsed electric current can be used for the fast sintering of powders as well as joining of macroobjects. In this work, we brazed copper plates using a silver layer that was formed in situ by the decomposition of a silver oxalate Ag2C2O4 powder placed between the plates. Joining was conducted in the chamber of a Spark Plasma Sintering (SPS) facility with and without a graphite die. In the die-assisted tooling configuration, indirect heating of the assembly from the graphite die carrying electric current occurred until the brazing layer transformed into metallic silver. The passage of electric current through a Cu/Ag2C2O4/Cu stack placed between the electrodes without a die was possible because of the formation of Cu/Cu contacts in the areas free from the Ag2C2O4 particles. Joints that were formed in the die-assisted experiments showed a slightly higher shear strength (45 MPa) in comparison with joints formed without a die (41 MPa). The shear strength of the reference sample (obtained without a die), a stack of copper plates joined without any brazing layer, was only 31 MPa, which indicates a key role of the silver in producing strong bonding between the plates. This study shows that both die-assisted tooling configurations and those without a die can be used for the SPS brazing of materials by the oxalate-derived silver interlayer.

In this study, the structure of explosively welded Ni–Al multilayer composites was investigated. In particular, the interface between Ni and Al plates was studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). Continuous interlayers of mixed Al and Ni were found at the interface. The Al and Ni in these zones were heated above their melting temperatures, non-uniformly mixed, and rapidly solidified. Several intermetallic phases, including the decagonal phase and metastable Al9Ni2, were observed in these zones using electron diffraction. A cellular dislocation structure formed in the Ni plates and a polygonized dislocation structure formed in the Al plates due to the extremely high strain rate deformation and heating. Subsequent heat treatment at 620 °C led to the rapid formation of stable intermetallic layers at the interfaces. The growth of the intermetallic layers was considerably faster in the explosively welded composite than in the reference sample. Keywords: Explosion welding, Composite, Intermeltallics, Quasicrystals

In this study, new multilayer TiAl-based composites were developed and characterized. The materials were produced by spark plasma sintering (SPS) of elemental Ti and Al foils and ceramic particles (TiB2 and TiC) at 1250 &deg, C. The matrix of the composites consisted of &alpha, 2-TiAl and &gamma, TiAl lamellas and reinforcing ceramic layers. Formation of the &alpha, 2 + &gamma, structure, which occurred via a number of solid&ndash, liquid and solid&ndash, solid reactions and intermediate phases, was characterized by in situ synchrotron X-ray diffraction analysis. The combination of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis revealed that an interaction of TiC with Ti and Al led to the formation of a Ti2AlC Mn+1AXn (MAX) phase. No chemical reactions between TiB2 and the matrix elements were observed. The microhardness, compressive strength, and creep behavior of the composites were measured to estimate their mechanical properties. The orientation of the layers with respect to the direction of the load affected the compressive strength and creep behavior of TiC-reinforced composites. The compressive strength of samples loaded in the perpendicular direction to layers was higher, however, the creep resistance was better for composites loaded in the longitudinal direction. The microhardness of the composites correlated with the microhardness of reinforcing components.

The hardening of VT1-0 titanium is studied during the formation of a multilayer material by explosion welding. The structural transformations in titanium plates are analyzed by metallographic and electron-microscopic methods. The mechanical properties of the welded multilayer titanium stacks are estimated using static and dynamic mechanical tests.

The structure of composites formed by explosive welding of thin sheets of tool and austenitic steels was studied by structural analysis methods. It is shown that the quenching and tempering of composites leads to the formation of complicated structure containing, along with layers of dissimilar steels, layers with new chemical compositions. Due to the structural changes there is an 2-fold increasing of impact toughness.

The structure and microhardness of Cu-Ta joints produced by explosive welding were studied. It was found that, during explosive welding, an intermediate layer μm thick with a finely dispersed heterophase structure, formed between the welded copper and tantalum plates. The structure of the layer was studied by scanning and transmission electron microscopy. Microvolumes with tantalum particles distributed in a copper matrix and microvolumes of copper particles in a tantalum matrix were detected. The tantalum particles in copper have a size of nm, with a predominance of nm particles. A mechanism for the formation of the finely dispersed heterophase structure in explosive welding is proposed. The microhardness of interlayers with the heterophase structure reaches 280 HV, which far exceeds the microhardness of copper (~130 HV) and tantalum (~160 HV). Many twins of deformation origin were found in the structure of the copper plate. The effect of heating temperature in the range from 100 to on the microhardness of copper, tantalum, and the Cu-Ta welded joint was studied. Upon heating to , the microhardness of the intermediate layer decreases from 280 to 150 HV. The reduction in the strength properties of the weld material is mainly due to structural transformations in copper.

A Ni3Al intermetallic compound was obtained by spark plasma sintering of mechanically activated Ni and Al powders in atomic ratio 3:1 respectively. Samples with boron addition of 0.1 and 0.2% (wt.) and samples without boron were obtained. The maximum value of the relative density (~99 %) has been obtained for the material by sintering of mechanically activated mixture powders modified with 0.1% of boron. No differences have been found between the structure of boron-modified Ni3Al and Ni3Al without boron addition. The maximum level of bending strength (2200 MPa) has been achieved for Ni3Al with 0.1% (wt.) of boron. This value is almost 3 times the bending strength of the sample of Ni3Al sintered without boron addition.

The structure of vortex zones formed by explosive welding of thin sheets of steel 20 was studied by structural analysis methods. It is shown that the main structural components of the vortices are fine-grained ferrite and martensite. The peripheral regions of the vortex zones are adjacent to layers of recrystallized ferrite with submicron-size grains. The presence of uniaxial dendrites suggests that, during explosive loading, the central region of many vortices were in a molten state. Intense mixing of the material in the vortex zones is responsible for the formation of voids, which account for 20 percent of the melt volume.

Approaches to protection of mother and child health in the USSR are outlined with special emphasis on the role of children's polyclinics. The law on childhood protection is based on 10 principles of Declaration on Children Rights adopted by the UN General Assembly in 1959. Current legislation provides for an increase in the duration of paid leave to care for the sick child up to 14 years of age, an increase in the monthly stipends to the children of military personnel, and free drug prescriptions for children up to 3 years of age treated as outpatients. From September 1, 1990, the duration of paid maternity leave for working women is 70 days. In light of a general legal reform currently conducted in the USSR, children's polyclinics as the primary link in the health care system are charged with protection of legal rights of mothers and children. Presently, 1.4% of all marriages in the USSR end up in divorce, so that every year 700,000 children younger the 18 years old are brought up in a single-parent family. Almost 85% of children in orphanages have live parents. Almost 200,000 children have criminal record, and 14,000 children are diagnosed to have sexually transmitted diseases annually. The legal work of children's polyclinics should be based on the evaluation of social risk factors. Following risk factors are identified: families with single mothers; families with 3 children; low-income families; families of the military personnel; families living in poor conditions; families with a history of death of a child 1 year old; disabled mothers; children of migrants or refugees; families in which one or both parent avoid the parental responsibilities or abuse their children.