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The article presents the results of a comprehensive study of the modes of laser processing during the formation of a coating on nickel-aluminum bronze using nickel powders. The coating was obtained in two stages. At the first stage, a precursor coating of the powder material was applied by cold spraying, at the second stage, its surface treatment with a laser was performed. The change in the composition and properties of the coating is shown depending on the processing modes and the thickness of the precursor coating, as well as the modes of laser processing.

Spent electroplating solutions contain small amounts of Pd(II). Cementation of Pd(II) with zinc metal powder is practiced to concentrate the Pd. Dissolution of the cemented Pd metal is necessary to recover pure Pd metal or compounds. In this work, the leaching behavior of Pd metal in inorganic acid solutions (hydrochloric and sulfuric acid) in the presence of an oxidizing agent such as H2O2, NaClO3, or NaClO was investigated. To determine the optimum conditions for Pd leaching, experiments were conducted by adjusting the concentration of the acids and oxidizing agents, reaction temperature and time, and pulp density. Complete leaching of Pd was possible using a hydrochloric acid solution with 3 kinds of oxidizing agents, whereas only NaClO was effective in the leaching with sulfuric acid solution. The chloride ions of HCl and NaClO3/NaClO play an important role in enhancing the leaching of Pd, due to the formation of Pd chlorocomplexes and by decreasing the reduction potential of Pd(II). Compared to H2O2, NaClO3 and NaClO showed some merits as oxidizing agents in terms of reaction time, temperature and low acid concentration. Based on the optimum leaching conditions of single Pd metal, the conditions for the complete leaching of Pd and Zn from the metallic mixtures were obtained.

A novel magnesium (Mg) production process utilizing an electrolytic method was investigated for the direct reduction of magnesium oxide (MgO). Electrolysis of MgO was carried out with an applied voltage of 3.0 V using a copper (Cu), silver (Ag), or tin (Sn) cathode and carbon (C) or platinum (Pt) anode in magnesium fluoride (MgF2)−calcium fluoride (CaF2)−sodium fluoride (NaF) at 1273 K or MgF2− lithium fluoride (LiF) at 1083−1093 K. After the electrolysis of MgO in MgF2−CaF2−NaF molten salt, Mg alloys such as Mg2Cu, Cu2Mg, or Mg2Sn phases were produced with current efficiencies of 75.8−85.6% when the concentration of Mg in Mg alloys was 9.1−14.6 mass%. In addition, when the electrolysis of MgO was conducted in MgF2–LiF molten salt, Mg alloys such as Mg2Cu or AgMg phase were produced with current efficiencies of 76.2−81.7% when the concentration of Mg in the Mg alloys was 12.5−13.2 mass%. In addition, to produce high-purity Mg metal from Mg alloys, vacuum distillation was conducted. When vacuum distillation was conducted at 1100−1400 K for a duration of 5 h, the concentration of Mg in the Mg alloys feed decreased from 30.2−34.1 mass% to 0.64−1.75 mass%, and Mg metal with a purity of 99.998−99.999% was obtained under certain conditions. Therefore, the molten salt electrolysis using liquid metal cathode (MSE-LMC) process developed here is feasible for the direct reduction of MgO using an effective and environmentally sound method.

The process of enrichment of potash ore using industrial oils as a hydrophobizing agent in the collective mixture of potassium chloride, which is a composition of salts of higher aliphatic amines, pine oil and polyethylene glycol PEG- 400, has been investigated. A comparative analysis of the influence of industrial oils I-8A, I-12A, I-30A and liquid paraffins on the technological parameters of potash ore flotation has been carried out. The influence of hydrophobizing additives on the adsorption of amine on potassium chloride crystals was investigated by infrared spectroscopy. It has been established that the introduction of industrial oils into the flotation system ensures the recovery of potassium chloride at the same level as when using a collective mixture with liquid paraffins. The best flotation performance when using industrial oils is possible by increasing the consumption of the apolar reagent.

The effect of Eu (Europium) element on eutectic Si in Al–7Si alloys was studied by scanning electron microscopy (SEM), thermal analysis, electron backscattering diffraction (EBSD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) to elucidate modification mechanism of Eu on eutectic Si. The results indicate that the addition of Eu changes the morphology of eutectic Si from coarse plate-like to fine fibrous. With the increase in Eu content, the number of eutectic cells gradually decreased and the size of eutectic cells increased. Meanwhile, the eutectic nucleation temperature (TN) and the minimum temperature (TMin) decreased, which is caused by the poisoning of AlP particles by Eu. The segregation of phosphorus was found at the center of coarse Al2Si2Eu particle, and the "phosphorus layer" was found at the boundary between the Al2Si2Eu particle and matrix. The length direction of plate-like eutectic Si was , and its outer surface was {111} plane. Few parallel twins were observed in unmodified plate-like eutectic Si. However, the growth of Eu-modified fibrous eutectic Si was isotropous. Multiply twins were often observed in fibrous eutectic Si after modification. The adsorption of Eu was observed along the Si growth direction of eutectic Si and at the intersection of two {111}Si twins, verifying the existence of the poisoning of the TPRE mechanism and IIT mechanism.

This study experimentally investigates the influence of adding SiC on microstructure and mechanical properties of the aluminium alloys welded joints. The SiC particles have been directly added into a zone of friction stir welding (FSW) to make (AA6061–AA2024) SiC composites material. Results show that the effect of adding SiC particles on microstructure refines the grain size in the stir zone by preventing its growth during FSW process. The adding of SiC particles has a significant effect on the thermomechanical zone resulting from restricting the growth of grains. Results indicated that the microhardness of FSW joints is increased from 44 to 86 HV by adding 9.2% SiC particles as compared to that obtained without including SiC under the same welding conditions. It has been observed that the tensile strength is enhanced when the amount of SiC particles are increased by up to 6.9%.

Purposeful control of structural state of steel at every stage of technological chain of steel goods production is necessary for elaboration of effective metallurgical technologies. The purpose of the complex of research and theoretical studies was development of ideas on peculiarities of structure formation of various steel grades. Current conceptions about phase and structural transformations in steels with different contents of carbon and alloying elements considered. For carbon and alloyed steels, the results of the study of the structure of perlite formed at different temperatures summarized; morphology, crystallography and defects of crystalline structure of cementite, processes of its fragmentation, coagulation and spheroidization; crystallography of austenite degradation products; evolution of the structure during cold and hot plastic deformation; carbon redistribution processes prior to and during diffusion-controlled austenite decay presented. For low-carbon low-and sparingly alloyed cold-resistant weldable steels generalized results of investigation of structure-formation processes, alloying relationships, temperature-deformation rolling conditions, parameters of quenching and high-temperature tempering with structure, mechanical properties and performance characteristics of steel plates presented. The elaborated complex of scientific and technical solutions based on the studies enabled to master and digitize production technologies at PJSC “Magnitogorsk steel-works” of new generation steel rolled products intended for ship-building, oil and gas industries, automobile, hardware and construction industries. The new systems of alloying steels of various application, methods of the new generation steels production and automated control of technological processes protected by 27 patents of RF, are widely used in the production activity of PJSC “Magnitogorsk steel-works”.

The present study was carried out to investigate the effects of Ni and Zr additions, individually or in combination, on the room-temperature tensile properties of 354 casting alloy (Al–9wt%Si–1.8wt%Cu–0.5wt%Mg) which was isothermally treated at temperatures in the range of 155–350 °C and aging times up to 1000 h. Tensile tests were carried out in the as-cast, solution heat-treated, and aged conditions using different aging times up to 1000 h. Quality charts were used as an evaluation tool for selecting the optimum conditions to achieve superior tensile properties and optimum quality in 354-type alloys. Zirconium reacts only with Ti, Si, and Al to form (Al,Si)2(Zr,Ti), (Al,Si)3(Zr,Ti), and Al3Zr phases. The beneficial effects of Zr and Ti additions appear in the refining of the α-Al grain size which reduces the size of the Al2Cu and α-Fe particles. Tensile test results at ambient temperature show a slight increase in alloys with Zr and Zr/Ni additions, particularly at aging temperatures above 240 oC. It is suggested that the maximum obtainable quality index values by means of heat treatment are the difference between the quality index values for the as-cast and solution heat treatment conditions.

Cu–6.5% Al alloys and Cu–6.5% Al alloys containing small amounts of silicon (Si) and manganese (Mn) were deposited using wire arc additive manufacturing (WAAM) by feeding two different components of wires simultaneously into the molten pool. The deposited alloys were homogenized by heat treatments at 800 °C (2 h). The effect of addition of Si and Mn on the microstructure and mechanical properties of Cu–6.5% Al alloys were investigated. Microstructural and formation of intermetallic compounds were studied. Results revealed that upon heat treatment, Si and Mn were able to restrain the dislocation movement due to the formation of second-phase particles. When compared to Cu–Al alloys, mechanical testing of the Cu–6.5% Al alloys having Si and Mn showed that hardness had increased by120 Hv, ultimate tensile strength (UTS) had increased by 284 MPa and yield strength (YS) had increased by 365 MPa, whereas its elongation (EL) had decreased by 22%.

The grain growth mode of titanium alloys remains controversial. In this study, ANSYS and cellular automaton-finite difference code μMatIC were coupled to simulate the multi-scale solidification process of commercial purity titanium and two types of titanium alloys with different solute concentrations. Investment casting of Ti–6Al–4V was carried out in counter-gravity casting method in vacuum environment. Results showed that the grain growth mode of titanium alloys depended on the solute compositions. Grain growth mode of titanium alloys transfers from planar to dendritic with the increased solute. The grain growth morphology of Ti–6Al–4V alloy presents cellular dendritic due to slight solute segregation in the solidification. The predicted grain structure was validated by comparison with the microstructural observation results. Both the prediction and experimental results revealed that equiaxed grains were obtained in investment casting of Ti–6Al–4V regardless of the thickness. The grain size increased with the wall thickness of the cast part.

The aim was to investigate the chemical composition of refinery slag obtained during silicon production in order to identify approaches to its further recycling. Research samples were collected from the slag remained after oxidation refining at the JSC Silicon (AO Kremny), RUSAL (Shelekhov, Irkutsk Oblast). The methods of X-ray phase, X-ray fluorescence, metallographic and scanning electron microscopy were employed to investigate the chemical composition of the samples. It was found that the refinery slag under study includes such basic components as elemental silicon, its carbide and oxide, as well as elemental carbon. It was shown that silicon carbide is the product of incomplete reduction, resulting from melting silica-containing ores in a smelting furnace. According to the conducted X-ray fluorescent analysis, the samples also contain (wt %): Ca - 7.40; Al - 3.80; Fe - 0.30; Ba - 0.19; K - 0.14; Na - 0.09; Sr - 0.09; Mg - 0.08; Ti - 0.05; S - 0.02. Calcium and aluminium are present in the slag mostly in the form of oxides. Complex oxides of an anor-thite type were also found: CaO Al2O3 2SiO2. The refinery slag under study also features insignificant amounts of other metal oxides, which are released from the furnace slag forming during the smelting process. The slag produced by oxidation refining during crystalline silicon production is a technogenic raw material containing valuable components. Due to the significant content of silicon in the refinery slag (from 42% to 65%), the existing methods applied to recycle such an industrial material were analysed in terms of additional silicon extraction or production of commercial silicon-containing products, which are in demand in various industries.

The possibility of raising the impact toughness of medium-manganese TRIP-steel Fe – 0.2% C – 6% Mn – 3% Al by application of a novel heat treatment involving quenching from the intercritical temperature range and subsequent tempering is investigated. Electron microscope and x-ray diffraction studies are performed after the heat treatment. The quenching mode providing the highest impact toughness is determined.

The surface layer obtained by ion-beam stirring of a thin carbon film deposited on titanium alloy VT6 is studied. The composition and the chemical condition of elements in the surface layer are determined. Formation of a disordered carbon structure in a thin surface layer (20 – 40 nm) and of titanium carbides in the transition layer is detected. A model of formation of structure in the specimens during irradiation is developed. It is shown that formation of a disordered carbon structure, of titanium carbides, and of dislocation substructures is responsible for elevation of the microhardness of the specimens after ion-beam stirring.

This paper deals with three types of triplex steel, where containing 25 to 28 wt.% manganese, 0.8 to 0.89 wt.% Carbon, 9.9 to 11.11 wt.% Aluminum, and with different Nickel content. Two types contain Ni in range of 0.9 to 2 wt.% and third type doesn’t contain Ni. The precipitation of Nano-size kappa carbides is the most proper technique used for this objective. It is expected that inter-metallic strengthening mechanism should act more effective in promoting the strength of Triplex steel with ductility. From this point of view, this research was designed to study the effect of inter-metallic inductive alloying element as Nickel on promoting of the strength and ductility of the high aluminum containing high manganese steel. Optical microscope, scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to detect of inter-metallic precipitates through steel investigated ranged in Nickel from 0 to 2 wt.%. Mechanical and strain hardening properties were determined in the steel investigated after different regimes of heat treatment. It was found that Ni3Al inter-metallic compound provides the austenite matrix with good strength and ductility, depending on the ageing time. Further deterioration was obviously observed in the steel investigated as increasing the ageing time, attributing to coarse structure occurrence.

This work explains the application of plasticized cellulose triacetate (CTA) membranes with Cyanex 272 di(2,4,4-(trimethylpentyl)phosphinic acid) and Cyanex 301 (di(2,4,4-trimethylpentyl)dithiophosphinic acid) as the ion carriers of lanthanum(III) and cerium(III). CTA is used as a support for the preparation of polymer inclusion membrane (PIM). This membrane separates the aqueous source phase containing metal ions and the receiving phase. 1M H2SO4 is applied as the receiving phase in this process. The separation properties of the plasticized membranes with Cyanex 272 and Cyanex 301 are compared. The results show that the transport of cerium(III) through PIM with Cyanex 272 is more efficient and selective than lanthanum(III).

The results of a study of the wear resistance of coatings based on cuprides of titaniumin the temperature range of 20-600 С are presented. It is shown that the wear resistance of nickel-doped coatings exceeds the wear resistance of binary coatings. With an increase in the Ni content of more than 10 %, their resistance to wear increases slightly.

Carbon steels can be sensitive to solidification cracking. Predicting their susceptibility to solidification cracking can save cost and time compared to testing, and it can be very useful for designing new steels or welds. Crack susceptibility predictions were made for carbon steels using the recently proposed simple susceptibility index for cracking during solidification, maximum │dT/d(fS)1/2│ near the end of solidification (T temperature and fs fraction solid). T vs. (fS)1/2 curves of the carbon steels were calculated by three different solidification models: equilibrium, Scheil, and Scheil with back diffusion of the available commercial thermodynamic software. The crack susceptibility predictions based on these solidification models were compared to various crack susceptibility test results of carbon steels, and the predictions based on Scheil with back diffusion were found consistent with the most of the crack susceptibility test results. Solidification temperature ranges of the carbon steels, determined based on the solidification models of equilibrium, Scheil, and Scheil with back diffusion, were used to explain the crack susceptibility predictions. The role of the alloying elements of the carbon steels in solidification cracking susceptibility was discussed.

In this paper, the nanoparticles (NPs) of magnesium oxide (nano-MgO) and silicon dioxide (nano-SiO2) and ultrasonication on the properties of sodium silicate bonded sand (SSBS) were studied, and the quantity of NPs and ultrasonication time in their interaction with sodium silicate binder were optimized by orthogonal experiment. This research was conducted with sodium silicate as a part of two-component (sodium silicate–silica fume) binder system to be used for heat-cured sodium silicate bonded ceramic sands. The results of experiment indicated that the addition of NPs and ultrasonication promoted the continuity and density of the bonding bridge of sand samples, the optimal quantity of nano-MgO and nano-SiO2 was 1.5% and 1.0% of sodium silicate binder, the optimal ultrasonication time was 15min, hot strength (σ0), 4-h tensile strength (σ4h) and 24-h tensile strength (σ24h) of modified sand samples increased by 11%, 25% and 27%, and the residual strength (σ800oC) decreased by 28%. The different linear expansion coefficients between nano-MgO, the new phase Na2Si3O7 and the sodium silicate system caused many cracks on the bonding bridge in the process of heating at 800°C and cooling, which resulted in the reduction of the residual strength of SSBS.

The article presents the study of the nature of dust and smoke generation during gas-oxygen blasting of a converter bath. The main reasons causing metal waste have been determined. Influence of the process main parameters on metal loss has been studied during dust removal and evaporation of iron in the reaction zone. The authors have estimated the process of metal pulverization due to CO bubbles floating, determined by the rate of their rise to the bath surface. Specifics of temperature regime of the reaction zone and heat balance have been determined when adding fuel to the oxygen flow. Adding fuel to oxygen makes it possible to increase heat input into the bath, while reducing the rate of decarburization. This enables reduction of dust discharge during rupture and crush of metal films by gas bubbles. The effect of combustion products oxygen use on metal impurities oxidation is considered. By the example of blasting carbon and alloyed steel for mill rolls, it has been shown that the degrees of CO2 and H2O decomposition in the bath are the main qualities of gas-oxygen blasting. These indicators determine the oxidizing and heating properties of the blast. Assessment of change in total, consumed heat and its losses with exhaust gases, depending on degree of the oxygen flow dilution with natural gas (methane), has been carried out. Under these conditions, use of submersible combustion torches with change in their oxidizing ability makes it possible to solve various technological tasks, including provision of an effective way to reduce dust emission in converter process.

The empirical equation to predict the heat-affected zone (HAZ) hardness of B-added steels has been proposed. For this purpose, weld thermal cycle simulation tests of both B-free and B-added steels in combination with hardness measurements were conducted. Firstly the previous HAZ hardness prediction equation was modified using the experimental results of B-free steels. Next, by introducing the B effect on hardenability to the modified equation, a new empirical equation to predict HAZ hardness of B-added steels was developed. The present equation takes into account the effects of peak temperature and Mo composition on B hardenability. The comparison of the predictions with the experiments of the weld thermal cycle simulation tests showed that the present equation can predict the HAZ hardness fairly well. The adjustable parameters of the B effect on hardenability introduced to the equation agree with the conventional results in the literature. To confirm that the present equation can be used to predict HAZ hardness of actual welded joints, hardness profile of welded joints was measured. The predicted HAZ hardness profile has shown to be in good accordance with the measured hardness profile.

The article examines a number of regularities in the production of primary cast ingots of AlSi7Mg, AlSi7MgSr, AlSi11Mg, and AlSi11MgSr. Peculiarities of melting and cast of these alloys, as well as the effect silicon and strontium have on the formation of the shrinkage cavities, have been explored. It has been demonstrated that strontium, when used as a modifier, changes not only the morphology of silicon, but also the nature of solidification and shrinkage of the alloy. Defects formed in the ingots manufactured from near – eutectic AlSi11MgSr alloy have been studied in greater detail.

This work presents studies on the material composition and physico-mechanical characteristics of an alumina-containing estimate formed during the production of aluminum on electrolyzers with self-baking anodes during technological operations. The material is a mixture of fine powder 2.5 mm in size (62.78% on average mass) with the presence of pieces of material ranging in size from 0.5 to 6 cm (average 20.26% by weight). The samples contain pieces of hardened aluminum with sizes from 5 to 20 mm (16.96%). The largest content in the sample has the fineness classes-0.315 + 0.16 mm in the volume of 29.85% and the largest class +2.5 mm-37.22%. B It was established that aluminum is concentrated in the fractions-0.315 + 0.16 mm (45.7%) and 0.16 + 0 mm (48.8%), silicon in the fraction-0.63 + 0.315 mm (1.91%), iron at-1.25 + 0.63 mm (0.601%) and-0.63 + 0.315 mm (0.62%). The material consists of cryolite (Na3AlF6), chiolite (Al3F14Na5), quartz, feldspar, carbonaceous matter and the technogenic phase of the composition (NaF) 1.5CaF2 AlF3. The material is characterized as non-abrasive (working index Ai - 0.0184) and very soft in relation to impact crushing (working index CWi - 3.64), the working index of ball grinding Bond (BWi - 6.47) characterizes a very low resistance to ball grinding. The implementation of the crushing operation of an alumina-containing estimate will allow the use of dry cascade-gravity and centrifugal classification to separate impurities in the form of SiO2, and Fe2O3 for the use of alumina-containing material in primary aluminum technology. On the basis of laboratory tests, it is established that alumina-containing raw materials can be separated and photometric and gravitational separation methods can be used. A mathematical model of the motion of particles of primary and prepared alumina-containing raw materials in a cascade-gravity classifier was developed. The criteria and factors characterizing the alumina-containing material, as well as influencing and determining the maximum material enrichment, are established.

XH 67 is a nickel-based superalloy, which is used in critical parts of modern aerospace engines. In the present study, XH 67 specimens in five different heat treatment conditions selected based on the processing and application have been investigated for their microstructures, morphology, and composition of the matrix and second-phase particles. Optical microscopic (OM) analysis revealed the presence of bi-model neck-lace type grains and equiaxed grains as a result of different heat treatment conditions. Scanning electron microscopy (SEM) and elemental composition analysis revealed precipitates and second-phase particles. Carbides such as Ti (N, C) and (W, Mo, Ti) C were observed having different sizes and shapes. Cr-rich carbide phases were found to be preferentially segregated along the grain boundaries. X-ray diffraction analysis was carried out for assessing the phases present in the alloy. X-ray diffraction analysis revealed the gamma matrix and the precipitate phase are crystallographically identical (coherent). Transmission electron microscopic (TEM) analysis of the specimens confirmed the presence of uniformly distributed spherical Ni3 (Al, Ti) precipitates which impart thermal stability to the superalloy. Presence of different types of carbides is also revealed by TEM analysis.

Aluminum is widely used in various industries in the form of alloys due to its unique properties - lightness, high electrical conductivity, and corrosion resistance. However, when casting alloys, various defects arise, the main of which are nonconformities of the ingot chemical composition, mechanical properties, and internal structure. The RUSAL Bratsk PJSC (, Irkutsk Region) aluminum alloy samples have been examined for pores, cracks, and oxide films. The causes of their occurrence have been analyzed and ways to eliminate these defects proposed. It has been found that, with increasing hydrogen content in the melt, micro-porosity leads to friability and macro-porosity of the alloy structure. According to the study results, the likelihood of cracks in the ingots could be reduced by evenly decreased metal temperature and casting velocity. The oxide film defects have been eliminated by feeding metal into the mold in a steady turbulence-free manner, increasing the metal settling time in a mixer, and reducing the alloy preparation time in a furnace.

The paper is devoted to the urgent issue of processing the dust waste of metallurgical-grade silicon production, i.e. wet cleaning sludge, which contains a significant amount of valuable silica. The paper analyzes the formation of finely dispersed techno-genic materials that are generated in significant quantities (up to 120 t/d) at the Kremniy JSC. The composition and properties of the silicon production wet cleaning product have been studied. In analytical studies of the wet cleaning sludge samples, the modern certified analysis techniques have been used: laser diffraction, X-ray diffraction, and X-ray fluorescence. According to the analysis, the L:S ratio of liquid sludge is 2.1:1; after dehydration, the sludge cake has a grain size of 150 μm, with the prevailing (90 %) grain size of 59.65 μm in the test sample. The chemical composition of the sludge is 95.86 % SiO2; therefore, the wet cleaning sludge is a valuable raw material to produce metallurgical-grade silicon. Based on the analysis of the composition and properties of the silicon production wet cleaning sludge sample, we have developed a program for its processing. Sustainable sludge processing techniques are aimed at obtaining a briquetted charge, which can be used as an additive to the main raw material.

Refill friction stir spot welding (refill FSSW) is one of the most industrially promising friction stir spot welding variants. The absence of an exit hole improves the effectiveness of surface treatments and minimizes damage by fouling. Aerospace aluminium alloys AA2024-T3 and AA7075-T6 with a thickness of 2 mm were used in this investigation. A range of values for rotation speed and plunge depth were experimented to determine the most promising process parameter combination based on the cross-sectional analysis and lap shear strength. The effect of an interfacial sealant on the weld properties was determined for both alloys using the most promising process parameter combination. Fatigue life analysis and fractography using scanning electron microscopy were performed for specimens with and without sealant.

A non-dendritic microstructure normally forming the products made by the controlled diffusion solidification process (CDS) has been studied. Samples from Al-4.7 wt%Cu, Al-8 wt%Cu, and Al-4.7 wt%Zn were made via the CDS process by mixing pure aluminum into Al-Cu and Al-Zn binary alloys at a different mass ratio. ANSYS software was employed to predict the distribution of the mixed alloys during the mixing step. The simulation results show that the mixed alloys breakdown to different size pockets. The higher mass pockets fall into the bottom sample after the mixing step resulting in effect the microstructure forming in the entire sample. The experimental results indicate that globular mixed with rosette and dendritic morphologies form the entire microstructure, although all the morphologies were exposed to the same thermal environment during growth. The results show that the globular morphologies form in the undercooled alloy that have a higher liquidus temperature, while the dendritic morphologies form from the alloy that has a lower liquidus temperature, which is heated during the mixing.

The oxy-acetylene torch brazing of copper tubes using silver-based filler metals (Ag-Cu-Zn-Cd) was investigated in this study. Filler metals containing silver content of 15% and 35%, designated by BR15 and BR35, were used to assess the influence of the silver content in the microstructure and mechanical performance of brazed joints. The brazed joints microstructure was analyzed by means of optical microscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The microstructures of the BR15 and BR35 samples were composed mainly of Ag–Cd-rich phase, solid solution of Cu–Zn, and a eutectic structure of Ag and Cu. The increase in the Ag content changed the solidification mode from cellular to dendritic and caused an increase in the eutectic phase volume fraction. The tensile strength of the Ag–Cu–Zn–Cd filler and the phos–copper filler metals was compared. The tensile strength of silver-based filler metal was slightly higher than the phos–copper filler metal brazed joints.

This paper has developed a new compound curing agent powder for a modified phosphate binder (3 wt% of raw sand). This combination can be self-cured and achieve relatively high bonding strength. The optimal composition ratio of curing agent powder is fused magnesia powder:silica fume:sodium polyacrylate at a ratio of 6:6:5, respectively. In this case, the tensile strength of phosphate binder sand sample at 4 h and 24 h is 0.65 MPa and 1.27 MPa, respectively. Infrared spectroscopy and scanning electron microscopy were utilized to analyze the variation of functional groups and the morphology of bonding bridge fracture of phosphate bonded sand samples after the addition of curing agent (fused magnesia powder, silica fume and sodium polyacrylate). The result shows that fused magnesia powder, silica fume and sodium polyacrylate all participate in the polymerization and curing reaction of phosphate binder; furthermore, sodium polyacrylate can effectively mitigate the propagation of cracks on bonding film.

The features of phase formation during the joint aluminothermic reduction of titanium, niobium, tantalum, and vanadium from their oxides are studied using thermodynamic modeling and differential thermal (DTA) and X-ray diffraction phase analysis. Using computer thermodynamic modeling made it possible to predict the optimal temperature conditions in the metallothermic process, the composition and ratio of the reagents in the charge, the behavior of the elements, and the sequence of the phase formation. To identify the kinetic and thermochemical components of the process, thermodynamic calculations are supplemented by differential thermal studies using combined scanning calorimetry. An analysis of the theoretical and experimental data shows that the interaction of aluminum with titanium dioxide proceeds through the stage of formation of titanium monoxide and results in the formation of TixAly intermetallic compounds of various compositions (TiAl3, TiAl, and Ti2Al) depending on the Al to TiO2 ratio in the batch. When titanium dioxide is partially replaced by niobium, tantalum, and vanadium oxides, the metallothermic process under interactions in the Al–TiO2–Nb2O5, Al–TiO2–Ta2O5, and Al–TiO2–V2O5 systems is of the similar character; enters the active phase after the formation of liquid aluminum; is accompanied by exothermic effects; and is characterized by the priority formation of titanium aluminides and binary and ternary intermetallic aluminum compounds with rare refractory metals of group V such as AlNb3, Al3Nb, Al3Ta, Al3(Ti1 – х,Taх), Al3(Ti,Ta), and Al3(Ti0.8V0.2). The joint conversion of titanium dioxide and rare refractory metal pentoxides during the reduction process is affected through sequential and parallel stages of the formation of simple and complex element oxides with low oxidation states.

Tantalum and palladium were added to Inconel 718 at the expense of Nb content to study resultant microstructure and mechanical properties in hot-worked and annealed condition. An increase in {100} peak intensity along with a concomitant decrease in {111} peak intensity was observed with decreasing Nb content. Ta-containing alloys exhibited annealing twins and annealing twin density showed a direct relationship with Ta content. Overall, alloying additions improved strength as well as ductility except the alloy containing only Ta which was less strong than Inconel 718. The alloy containing Ta as well as Pd exhibited highest toughness and lowest Rockwell hardness value.

This research investigates the nickel content added by 1.1wt%, 2.2wt%, 3.7wt% and 4.5wt% on the microstructure and mechanical properties in the nodular cast iron. The results demonstrate that the microstructure of nickel addition consists of nodule graphite, ferrite and pearlite phase while nickel was added to 4.5 wt% the microstructure becomes ferrite transform to fully pearlite phase. In addition the ductile iron has the highest nodularity (0.79%), followed by 1.1%Ni (0.75%), 2.2%Ni (0.71%), 3.7%Ni (0.69%) and 4.5%Ni (0.58%). The hardness and tensile strength increase when increasing the nickel content. Elongation is enhanced with nickel increasing and reaches a maximum of 12% at 1.1 wt% Ni, then decreases with the further increase of nickel.

The main mechanisms of structure formation in zones of welded joints of unlike metals (steel – aluminum) obtained by friction stir welding in the mode of structural superplasticity are considered. Sheet billets of different steels (St3ps, 12Kh18N10T) and deformable aluminum alloys (AD1, AMg6) with a thickness of 3 mm are butt- and lap-welded by the friction stir technique. The microstructures, the phase components and the mechanical properties of the welded joints are determined.

Long-length bimetallic conductors with a copper core and a shell from an aluminum alloy up to 2.4 mm in diameter with enhanced strength are obtained by swaging. The effect of the swaging strain on the structure, phase composition and mechanical properties of the bimetallic conductors is studied.

The methods of transmission and scanning electron microscopy are used to study the evolution of the structure of a welded joint of steels 32G2 and 40KhN in the thermomechanically affected zone (TAZ) under rotary friction welding (RFW). EBSD analysis is used to certify the microstructure in different parts of the TAZ and to calculate the densities of the low- and high-angle boundaries. It is shown that complex processes of dynamic recrystallization combining several mechanisms develop in all these regions of the TAZ. Typical differences in the structures of the mobile (steel 40KhN) and immobile (steel 32G2) parts of the billets are described.

Experimental studies have been carried out with theoretical calculations of wave synthesis in the Ni–Al–Cu system using a mathematical model. Approximate analytical formulas are obtained for synthesis performance evaluation. The inverse problem method was used to get kinetic constants that determine process dynamics based on the experimental data and analytical relationships. It is shown that the combustion front propagation velocity increases monotonically with an increase in the reaction sample relative density in the range of relative density values of 0.4 to 0.6. The depth of copper-melt penetration from the center of the sample into the nickel–aluminum matrix depends on the relative density of the sample and diameter of the copper wire: higher densities and larger diameters lead to an increase in the liquid-phase impregnation area. The rate of nickel and aluminum powder frame wetting with copper melt is limited by the synthesis wave speed. Based on the experimental data and analytical ratios, we estimate the effective kinetic constants describing the high-temperature synthesis of the Ni + Al reaction mixture in the presence of copper additives. The thermal effect of the NiAl intermetallic formation reaction and the preexponential factor in the chemical transformation equation are calculated, the exponent value in the ratio for the mixture thermal conductivity is established, and a constant determining the process of nickel–aluminum matrix impregnation with copper melt is found. The macroscopic approach used to analyze the NiAl intermetallic synthesis makes it possible to determine all the desired physicochemical characteristics and model parameters. The mathematical model is suitable for predictive estimates and experimental data analysis in the macroscopic approximation. Approximate analytical formulas are obtained for calculating the NiAl intermetallic synthesis characteristics. They allow for calculating the through channel characteristics and can be used in the design of NiAl products.

Examination of fractures of rolling bearings from steel 8Kh4V9F2-Sh (EI347-Sh) is used to assess the effect of production factors on the operating capacity of bearings under elevated loads. The microstructure and fractures of the steel are analyzed. The compressive stresses and the contents of the general and diffusion-mobile hydrogen are determined. It is shown that a fatigue crack appears in the material of the bearing in service in the case of an elevated hydrogen content and an unfavorable fiber structure.

At the Navoi Mining and Metallurgical Combine, which uses a large number of machine parts for mining operations, the issue of optimizing the compositions of wear-resistant chromium cast irons while maintaining their operational characteristics has arisen. The paper presents the results of studying the phase composition of the cast alloy, as well as the effect of heat treatment of cast iron with a high chromium content on its structure and properties. As heat treatment operations, quenching in various modes and low tempering were used. The study made it possible to systematize the known literature data on the heat treatment parameters of a group of wear-resistant chromium cast irons, as well as to optimize their heat treatment modes for parts operating in mining and processing industry.

The present work was undertaken with the aim of studying the microstructural changes and intermetallic phases in Al-Si base 413.0 alloys as well as variations in tensile properties, including ultimate stress, yield strength and elongation at rupture, resulting from the addition of alloyed elements: strontium (Sr), magnesium (Mg), copper (Cu), silver (Ag), zinc (Zn) and nickel (Ni), to the base alloy 413.0, under different conditions of heat treatments, i.e., solutionizing and artificial aging (in the temperature range of 155 °C–240 °C). The results obtained in relation to microstructural observations and tensile tests reveal that the addition of alloying elements, in particular Mg, Cu, Ag, Ni, Zn and Sr, leads to an increase in the ultimate stress and yield strength values with a decrease in the strain levels of the base alloy 413.0, following hardening during artificial aging. Both Ag and Zn do not form specific phases during solidification at a slow rate of ~ 0.8 °C/s but only segregate to the α-aluminum cell boundaries. Addition of 0.73% Ag improves the values of yield strength at all aging temperatures. Also, it enhances the alloy resistance to softening during aging in the temperature range 200–240 °C. Similar behavior was exhibited by the addition of 2.5% Zn.

The microstructure, the phase composition, the microhardness and the wear resistance of hypoeutectic white cast irons with different contents of chromium are studied. It is shown that the wear resistance of the iron depends substantially on the type of the carbide phase and on the morphology of the ledeburitic eutectic, which is determined in its turn by the content of chromium.

With China’s bauxite resources depleting year by year, high-alumina fly ash has been regarded as a potential secondary aluminum resource, with alumina content as high as 40–60%. In view of recognized problems, such as large amounts of circulating acid and environmental pollution in the process of extracting alumina from high-alumina fly ash, Northeastern University has proposed a new electrotransformation method. This method has the main advantages of slag reduction, no waste acid, no waste alkali, and recycling. In this study, the effects of diffusion were examined during electrotransformation, in terms of electrode spacing and concentration difference on solution pH and temperature. In addition, the phase, FT-IR results, roasting weight loss rate of products, D(50), D(90), isothermal adsorption and desorption curves, BET surface area, pore volume, impurity chlorine content of roasted products, and Al recovery rate were investigated. The results showed that pH and temperature increased with prolonged electrotransformation time. And that these products were all amorphous containing-carbon aluminum salt precipitation. Roasted products were all alumina (Al2O3) with a steep broad X-ray diffraction peak. The effects of electrode spacing and concentration difference on isothermal adsorption and desorption curves, BET surface area, and pore volume were not clear. With decreased electrode spacing, the Al recovery rate increased and impurity chlorine content decreased. With increased concentration difference, the Al recovery rate tended to first decrease and then increase, while the impurity chlorine content increased. In other words, small electrode spacing and high concentration difference were beneficial for improving the Al recovery rate.

The phase transformation behavior of lead and zinc in the high-lead slag reduction process was reported in this article. First, the occurrence state of lead and zinc in the slag and the phase transformation behavior of lead and zinc during reduction were investigated. Following, the thermodynamic modeling calculation for the reduction process was constructed and discussed. The results indicated that the zinc in the high-lead slag mainly existed in the form of zinc ferrite and silicate while the lead mainly existed in a silicate form. The XRD patterns of the reduced slag at different coal ratios demonstrated that the lead existing in the high-lead slag in a silicate form could be reduced into the metal phase while the zinc existing in the high-lead slag in the form of zinc ferrite (ZnFe2O4) could be converted into zinc silicate (Zn2SiO4), as the coal ratio increased. The thermodynamic modeling calculation results showed an agreement with the experiment analysis.

In this work, an experimental modeling of the technology for producing a matrix by sintering a diamond-containing briquette with a filler of tungsten monocarbide powder impregnated with a Fe-C eutectic melt in a vacuum is carried out. The microstructure, elemental and phase compositions of the products formed in the process of sintering a diamond-containing matrix with impregnation with a Fe-C eutectic melt in vacuum have been studied by scanning electron microscopy, X-ray spectral and X-ray phase analyzes, and Raman spectroscopy. It was found that the matrix consists of 61.0% tungsten carbide phases, 17.0% of iron carbide, 16.5% of α-Fe, and 5.5% of graphite. The eutectic Fe-C alloy, which serves as a matrix binder, consists of a ferrite-pearlite metal base with graphite inclusions. It is shown that at the diamond - matrix interface, graphite inclusions are formed not as a continuous layer, but as discontinuous areas along the perimeter of diamond grains. The microhardness of the WC-based matrix impregnated with the Fe-C melt is ~ 11 GPa, which is more than 3 times higher than the microhardness of the WC-Co-Cu hard alloy matrix obtained by sintering with copper impregnation.The research results can be used in the development of technology for the manufacture of wear-resistant matrices of diamond tools of a wide class used in the processing of materials with a high level of hardness.

The paper describes an extensive study of features peculiar to physical and mechanical processes occurring in metal in the deformation zone during the continuous extrusion of Cu-ETP rectangular busbars 10×60 mm in size. Finite element computer simulation was used to obtain the values of extrusion power parameters. It was noted that moment and force values increase to the point of filling the press chamber free space with metal reaching a maximum of 12.26 kN·m and 1.54 MN, respectively. The stress-strain state analysis of metal in the deformation zone made it possible to obtain distribution fields of accumulated plastic strain, strain rate intensity and average stresses, and to build the graph of metal temperature variation over time during extrusion. Maximum levels of accumulated plastic strain and compressive stresses are observed in the contact zone of the workpiece with the press container abutment. The most intense metal deformation heating also occurs there. The comparison of modeling and microstructural study results indicate that a significant portion of the cast structure grinding work occurs at the entrance to the deformation zone and at the abutment zone subjected to the highest level of compression stresses. Metal deformation during the die passage leads to an oriented crystal structure formed with a grain size of 25–30 μm. Sample hardness measurement results are consistent with the results of structure analysis in the studied areas of the deformation zone. When the workpiece passes through the compression container abutment section, deformation heating occurs, which leads to a decrease in hardness from 93 to 67 HV. After the metal passes through the die, recrystallization processes continue in it leading to a slight increase in grain size and, accordingly, a decrease in hardness from 79 to 74 HV, which continues until the busbar contacts a cooling medium.

This paper discusses the effect of different combinations of preheating and post-heating on the corrosion and hydrogen embrittlement of Grade-91 steel weld joint in the as-welded condition. Though these welds are subjected to post-weld heat treatment (PWHT), there could be long delay in executing this, especially in the case of fabrication of large components, and during this delay, the welds in as-welded conditions are prone to environmental degradations like hydrogen embrittlement and different forms of corrosion. Though recommended minimum preheating and post-heating conditions are already known for welding of this class of steels, marginally increasing the temperature of preheating and post-heating or increasing the duration of post-heating can permit longer delay in the post-weld heat treatment (PWHT), without increasing the risk of environmental degradation. With this objective, a set of thirteen single-V multi-pass gas tungsten arc weld joints of Grade-91 steel fabricated with different preheating and post-heating combinations. Results indicated a significant reduction in residual tensile stresses in the weld metal and reversing into compressive stresses upon preheating and post-heating at 300 °C. Moreover, diffusible hydrogen content and corrosion rate decreased significantly with the preheating and post-heating. However, there are no significant variations in the microstructure, mechanical properties, and hydrogen embrittlement with preheating and post-heating. This study proved that the risk of embrittlement in Grade-91 steel welds due to an indefinite delay in PWHT could be minimized by combined preheating and post-heating.

The lightweight construction of steel structures is often limited by the mechanical properties of the weld metal. The strength values of modern base materials are not achieved in the weld metal. There is a considerable need to develop welding consumables that allow the processing of modern fine-grained structural steels without limiting their potential. The Physical Vapor Deposition (PVD) coating of welding wire electrodes can increase the strength of the weld metal of a Mn4Ni2CrMo welding wire electrode by up to 30%. By using different coating elements, the Hall–Petch relationship can be exploited and such an increase in strength can be achieved. Especially by applying titanium, vanadium, and yttrium coatings, the strength of the weld metal can be increased. Due to a multilayer structure of the coating, the weld metal and the process can be influenced independently of each other. The effects of mono-element coatings and multi-component coatings on the weld metal and the process are discussed. PVD coatings allow welding wire electrodes to be individually adapted to the requirements.

Available fatigue recommendations are typically developed for arc-welded joints. Some of them may need to be adjusted to fit fatigue life of joints manufactured with non-conventional welding techniques since they show different mechanical properties. Laser beam and friction stir welded butt and overlap joints made from aluminium are addressed in this paper focused on a comparison between different fatigue assessment methods. For an evaluation, S-N data from published papers was collected. Additionally, fatigue tests on laser beam and friction stir welded overlap joints were carried out. For a fatigue assessment, the nominal stress, notch stress and effective stress approach were applied. The comparison of the endurable nominal stresses showed a comparatively high fatigue strength of the tested friction stir welded overlap joints in comparison to literature data. The notches at the interface of the overlap joints were observed to have an asymmetric geometry compared to the common symmetric one, frequently found in literature, leading to a lower stress concentration. A comparison between endurable nominal stresses and the classes FAT 28 for butt welded and FAT 12 for overlap welded joints resulted in a conservative design for the majority of specimens. An evaluation based on notch stresses lead to partly non-conservative results that could be explained by the mild notches present at the laser-beam welded butt joints. For the effective stress approach, an evaluation of the micro-structural length was performed and a FAT-value is proposed.

The effect of heat treatment on the microstructure and metallurgical properties of the interface between copper and austenitic stainless steel 304 formed by explosive bonding using different conditions of stand-off distance and material thickness was studied. Laboratory studies were carried out using optical microscopy, scanning electronic microscopy, and microhardness measurements to evaluate welded samples. Samples were subjected to heat treatment in a furnace at 300 °C for 22 or 30 h, then cooled in air. Microstructural studies showed that, as the stand-off distance and explosive load were increased, the interface between copper and stainless steel 304 became more wavy. The microhardness results showed that the hardness of the base metal was greater than in other areas near the interface because of extreme plastic deformation due to the explosive force. The results also showed that, as the temperature and heat treatment duration were increased, the hardness of the flyer plate at the interface decreased compared with before heat treatment.

The hot tearing susceptibilities of an Al–Si based alloy were investigated for hot tearing characteristics. The experimental studies were conducted using a newly developed enhanced constrained rod casting method that enables real-time measurements of the contraction load developed in the casting and the temperature variations during solidification as a function of time. A304 and A380 casting alloys were selected to study hot tearing characteristics at pouring temperatures of 700 °C, 750 °C, and 800 °C. The study showed that hot tearing was not observed in measurement rod of A304 and A380 casting alloys. However, hot tearing was observed in the constrained rods A and B of A380 casting alloy at 750 °C. A304 alloy showed higher resistance to hot tearing at a casting temperature below 750 °C.