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Abstract—WC–Co composite is one of the most popular and widely used. To improve some functional properties, thermal conductivity, corrosion resistance, etc., a search is underway for alternative metal binders with the possible replacement of Co with copper to reduce sintering temperatures and provide a higher thermal conductivity of the composite. Previously, it was shown that melt impregnation of freely poured refractory powders into a crucible-mold, activated by low-frequency vibration (LFV) of their compositions, differs from the methods used in industry in the simplicity of technology, short duration, and the possibility of obtaining composites with a high content of refractory phase with its frameless packaging. Two- to three-layer WC–Cu/Cu and Cu/WC–Cu/Cu composites with different arrangement of the working WC–Cu layer along the height of the ingot and different structural characteristics and properties of the layer have been obtained. The influence of thermal temporal conditions of LFV, pressure of cold prepressing of WC powder, dilution of carbide powder with copper powder, and geometry of stacking of alloy components on the formation of a given lamination of a composite alloy, a given composition, and a minimum porosity of the WC–Cu working layer was analyzed. The hardness and wear resistance of the WC–Cu layer were measured and their relationship to the layer structure and controlled parameters of the composite synthesis process control was established. Both the porosity of the structure and the presence of dense macroaccumulations of WC in the Cu matrix can be reduced to a minimum by preventive small prepressing of freely poured powders at room temperature before loading the alloy components into the furnace, followed by processing of the vibration. Composites with a homogeneous structure and low porosity of the working layer have been obtained. [ABSTRACT FROM AUTHOR]

Abstract—The thermochemical properties of the Al–Er system are investigated. The thermodynamic characteristics ( , , (), Cp(T), Cp(liq)) of the intermetallic compounds Al3Er, Al2Er, AlEr, Al2Er3, and AlEr2 are estimated. For calculations, we used the values of calculated on the basis of a semiempirical Miedema model adapted for an Al–REM alloy group; they are found to be –47.7, –58.4, –63, –55.2, and –46.8 kJ/(mol at), respectively. To estimate the mixing characteristics of liquid alloys of the system, we use the Terra software package for modeling the equilibrium states of heterogeneous inorganic systems, which is coupled with an extensive database of the properties of individual substances. The model of ideal solutions of interaction products is applied for calculations. The equilibrium composition and the properties of melts are modeled in the temperature range 1900–2100 K in the initial argon medium at a total pressure of 0.1 MPa in the system. A comparison of the obtained results with the results simulated in the ideal solution approximation makes it possible to determine the excess integral thermodynamic properties of liquid alloys (Gibbs energy, enthalpy, entropy). When the temperature increases in the range under study, the absolute values of these properties are shown to decrease weakly and regularly. The formation of liquid Al–Er alloys is found to be accompanied by significant heat release: the integral enthalpy of mixing at T = 2100 K is –58.27 kJ/(mol at). When comparing the thermochemical properties of the Al–Er system with the binary systems Al–Y and Al–Sc studied by the same methods, we can see that all energy curves pass through an extremum at XSc, Y, Er ≈ 0.5. The strongest interaction of the components is observed in the Al–Y system (ΔHmix= –58.9 kJ/(mol at)), which is close enough to the maximum absolute value of the enthalpy of mixing in the Al–Er system. The weakest interaction is observed in the Al–Sc system (ΔHmix= –44.8 kJ/(mol at)). The results obtained in this work provide a theoretical basis for a further experimental study of erbium-containing aluminum alloys. [ABSTRACT FROM AUTHOR]

Abstract—The possibility of increasing the hardness of a Co–Cu binder in single-stage production of WC–Cu–Co composites using pre-solidification low-frequency vibration (LFV) is investigated. Cu–Co and WC–Cu–Co alloys are fabricated by reactive infiltration of liquid copper into uncompacted WC and Co powders under LFV of their compositions (80 Hz for 10 min at 1300–1350°C). Their phase and chemical compositions, structure, and hardness have been studied. We are the first to experimentally show that metastable formations (frozen immiscibility regions of two liquids) are the precursors of (Co) dendrites and have the same composition with them. The cobalt distribution over the height of Cu–Co alloy ingots and over phase components is shown to depend on the cobalt content, the effect of vibration, the geometric arrangement of initial component layers, and the temperature. The optimum conditions for achieving a uniform cobalt distribution over the melt have been determined. Cobalt is shown to ensure precipitation hardening of the Cu–Co metal binder due to the formation of (Cu) solid solutions already at the stage of synthesis of Cu–Co and WC–Cu–Co alloys. Moreover, the potential for additional hardening by subsequent heat treatment or by changing cooling conditions is still incompletely fulfilled. [ABSTRACT FROM AUTHOR]

In this work, the arc resistance of electrical contacts of the compositions WC–Cu, Cr3C2–Cu, and WC–Cr3C2–Cu (with a mass ratio of WC : Cr3C2 = 1 : 1) was studied in comparison with the industrial contact D30V70, and an analysis was made of the dependence of functional properties on the composition and contact structures. Experimental samples of electrical contacts were obtained by liquid-phase impregnation of noncompacted carbide powders with copper at low-frequency (~80 Hz) vibration of the crucible with alloy components for 10 min in a resistance furnace in an atmosphere of flowing argon. Prepared samples were tested using equipment that simulated the operation of an AC contactor (170 A, 50 V, 1000–10 000 arcing cycles). Their functional properties (hardness, arc wear, contact resistance) were studied. The evolution of the structure was studied using optical and electron microscopy. It is shown that alloys containing WC or WC + Cr3C2 have stable values of contact resistance (up to 10 000 arcing cycles). Alloy WC57Cu43 (wt %) has the highest arc resistance, which not only is comparable with the industrial alloy but also surpasses it in long-term tests, despite the lower content of the arc-resistant phase. In contacts of the Cr3C2–Cu composition, the contact resistance increases and grows most sharply after 4000 arcing cycles. In contacts made of bicarbide alloy WC–Cr3C2–Cu, the degree of increase in contact resistance is similar to the industrial alloy, but the average values are higher. The wear layers of monocarbide alloys are highly oxidized. In a bicarbide alloy, there is no oxygen in the composition of such a layer. The composition of this alloy is represented by solid solutions of metals and their carbides, and the structure is finely dispersed. The mechanisms of arc resistance in electrical contacts of various compositions are discussed. [ABSTRACT FROM AUTHOR]

A composite material (CM) based on a copper powder clad with a Fe–Cu pseudo alloy (PA) for a working layer of two-layer interrupting electrical contacts was created using pressing, rolling, and sintering. The powder of activated carbon (CA) with the specific surface area of 1000 m2/g served as an arc quenching component, and highly dispersed powders of Al2O3, Fe2Al5, and Fe were used as additional components. The experimental linear dependences of the conductivity and hardness of copper-based composites on the concentration of particular functional additives of CA, PA, Al2O3, and Fe2Al5 were established. The addition of mixtures of these components was used to obtain CMs for the working contact layer of the following compositions (in wt %): 97% Cu + 1% СА + 2% PA and 97.5% Cu + 1% СA + 0.5% PA + 1% Al2O3 with the electrical resistivity of 3.20 and 4.5 μΩ cm and hardness HB of 1030 and 790 MPa, respectively. The dependence of the maximum allowable resistivity of the working layer (ρCM) on the ratio of its thickness to that of the copper layer was calculated for a given conductivity of a two-layer contact at a level of at least 75% of the copper conductivity. The characteristics of the CM with the composition 97% Cu + 1% СА + 2% PA make it possible to create an electrical contact for which the ratio of thicknesses of the working and copper layers is 1 : 1. [ABSTRACT FROM AUTHOR]

The influence of various schemes of pressure treatment (pressing, rolling) and modes of heat treatment of powder mixtures on the service properties and adhesion strength of the working and current-carrying layers of electrical contacts with a conductivity of at least 75% of the copper conductivity was studied. The dependence of the permissible fraction of the working layer in the total contact thickness on its resistivity was established. It was calculated that, in the created contacts, the thickness of the working layer of two compositions 97% Cu + 1% CA + 2% PA (1) and 97.5% Cu + 1% CA + 0.5% PA + 1% Al2O3 (2), with the electrical resistivity of 3.20 and 3.28 μΩ cm, respectively, can be increased to the thickness of the copper layer (here, CA is activated carbon; PA is a (Fe–Cu) nanocrystalline pseudoalloy). Among the considered processes, we determined the optimum method to fabricate contacts that consists of combined rolling with a reduction of 50% of copper powder and the powder mixture for the working layer using the metering hoppers separated for the charge of each layer, reducing sintering at 600°C for 1 h, and re-compacting rolling with strain of 85% and sintering at 800°С for 1 h. This technique was used to obtain samples of contacts with working layers of two compositions with a relative density of 0.99 and 0.98, hardness HB of 990 and 830 MPa, and electrical resistivity of 2.57 and 2.61 μΩ cm, respectively. The adhesion strength of contact layers is more than 200 MPa (breaking stress for copper). [ABSTRACT FROM AUTHOR]

We obtained WC–Cr3C2–Cu composite alloys by the copper melt infiltration into uncompacted WC and Cr3C2 powders (the reference alloys) and their mixtures with the weight ratio WC : Cr3C2 = 1 : 1. Impregnation of the uncompacted carbide powders with the copper melt was performed at low-frequency (~80 Hz) vertical vibration (LFV) of the crucible with the alloy components for 10 min in a resistance furnace under a flow-through argon atmosphere. We studied the influence of the heat treatment of the obtained model composites on interaction of the WС and Cr3С2 carbides under isothermal and dynamic temperature impact, as well as during high-speed cyclic heating of the alloy surface by an electric arc (120 A, 45 V, 2 Hz, 10 000 arc interruption cycles). We investigated the evolution of alloy structures by means of electron microscopy, X-ray spectral microanalysis, X-ray phase, and differential thermal analysis. We show that the impact on the sample surface by the temperature field created by the electric arc leads to intense interaction of the carbides. Here, the matrix copper transforms periodically into a melt and plays the role of a transfer medium (the diffusion medium). As a result of such heat treatment, in the upper layers of the alloys, finely dispersed compositions of complex carbide phases occurred with the sizes ≤1–2 μm, i.e., 1–2 orders of magnitude less than that of the initial carbides. [ABSTRACT FROM AUTHOR]

The thermodynamic characteristics of aluminum–yttrium melts are studied. An analysis and calculations of the thermodynamic properties ( , , (), cp(T), and cp(liq)) of the Al3Y, Al2Y, AlY, Al2Y3, and AlY2 compounds are performed. The standard enthalpies of formation of the intermetallics, which are calculated by the semiempirical Miedema model, are –49.4, –60, –63.4, –55, and –46.5 kJ/(mol at), respectively. The calculation results are used for the thermodynamic modeling (TM) of the Al–Y melts, which is performed using the TERRA software as a calculation tool. The modeling of the composition and thermodynamic characteristics of the melts is carried our using the model of ideal solutions of interaction products (ISIP). Based on this model, the thermodynamics of the aluminum–yttrium liquid solutions is studied. The modeling is performed for an initial argon atmosphere at a total pressure of 105 Pa. The temperature and composition range corresponding to the liquid state of the system (1900–2100 K) is studied. A comparison of the results obtained and modeling results obtained in the ideal solution approximation allowed us to determine the excess integral thermodynamic characteristics of the melts (enthalpy, entropy, Gibbs energy). The values of enthalpy of mixing are shown to decrease regularly as the temperature increases. The determined values are compared with the available experimental data on the integral enthalpies of mixing of Al–Y melts. The data obtained in the present study by calculation procedures demonstrate a trend toward the strongest interaction of the components over the entire composition range. In this case, the integral enthalpy of mixing reaches –59.6 kJ/mol. The energy curves obtained by TM have an extremum at XY = 0.46; the composition corresponding to this point is close to that of the AlY intermetallic compound. The experimental data indicate a weaker interaction of the components; the extremum corresponds to –49.6 kJ/mol. The data obtained in the present study agree well with the experimental data; the ISIP model used for TM allowed us to adequately describe the thermodynamic properties of the aluminum–yttrium melt. [ABSTRACT FROM AUTHOR]

An express method to activate the formation and decomposition of (Cr,W) solid solutions, which is based on copper melt infiltration into noncompacted mixtures of chromium and tungsten powders under low-frequency vibration, is used to form disperse structures in Cr–W–Cu alloys. Model composite alloys are fabricated at 1300–1450°C. Their macro- and microstructure and elemental composition are investigated. A short time of mixing of powders before infiltration results in microcomposites (MC) with compositions varying over a wide range in a copper matrix: the Cr/W ratio (at %) in them is 0.2–7.2 and the Cu content is 1–31 at %. The copper content in MCs is found to depend exponentially on the Cr/W ratio. The microstructure of MCs consists of (Cr,W) solid solutions and/or disperse products of their decomposition in α-Cu. Secondary globular tungsten forms below the binodal line and lamellar tungsten forms above it in an (Cr,W) matrix during low-frequency vibration. The degree of dispersion of globular tungsten increases when the copper content decreases and the chromium content increases in MCs. [ABSTRACT FROM AUTHOR]

Millions of tons of dust produced in the process of gas cleaning are accumulated in dumps located near metallurgical plants. Such dust contains harmful impurities (Zn, As, Pb, and P), thus its recycling by the agglomeration method can lead to either environmental contamination or furnace damage. Hence, prior separation of iron from the impurities is required to improve the efficiency of the recycling process. Here we propose a new hydrometallurgical scheme for extracting iron in the form Na3FeF6 from the liquid phase produced as the result of dust acidic leaching. The ability of Na3FeF6 to interact with NaOH (KOH) with the formation of Fe(OH)3 has been utilized for separating Fe3+ ions from F–. The proposed scheme is relatively simple, quick, and inexpensive, thus allowing its use at metallurgical plants to separate Fe from Zn, As, Pb, and P. [ABSTRACT FROM AUTHOR]

The thermodynamic characteristics of aluminum–hafnium melts are studied. The well-known (Δf ) thermodynamic properties are analyzed, and unknown ones ((), ( – ), cp(T), and cp(liq)) are calculated for the congruently melting Al3Hf, Al2Hf, AlHf, and Al2Hf3 compounds. The standard formation enthalpies of these intermetallic compounds are taken from the literature, where they were calculated using semiempirical Miedema's model and were –142.4, –134.1, –100.6, and –225 kJ/mol for each intermetallic compound, respectively. The calculation results are used for a thermodynamic simulation (TS) of Al–Hf melts. The thermodynamic simulation is performed using the TERRA software package. The composition and the thermodynamic characteristics of the melts are calculated using the model of ideal solutions of interaction products (ISIP). This model is used to study the thermodynamics of the liquid solutions in the aluminum–hafnium system. The simulation is carried out in an initial argon atmosphere at a total pressure of 105 Pa. The studies are performed in the region of temperatures and compositions corresponding to the liquid state of this system (2100–2300 K). A comparison of the results with the results of ideal solution approximation simulation makes it possible to determine the excess integral thermodynamic characteristics (enthalpy, entropy, Gibbs energy) of the Al–Hf melts. The enthalpies of mixing are shown to decrease in absolute value as temperature increases. The values found in this work are compared with the well-known data on the integral enthalpies of mixing for aluminum melts containing other III–IV group transition elements (Sc, Ti, Zr). The formation of Al–Hf, Al–Sc, Al–Ti, and Al–Zr liquid alloys is found to be accompanied by significant heat release. The extreme integral enthalpy of mixing of an Al–Hf alloy is comparable with that of an Al–Ti alloy and is no higher than –32 kJ/mol in absolute value. The components of the Al–Sc and Al–Zr systems demonstrate a tendency toward a stronger interaction: ΔHmix reaches –45 kJ/mol. The ISIP model used for TS makes it possible to describe the thermodynamic properties of the aluminum–hafnium melts. [ABSTRACT FROM AUTHOR]

The definition of random packings of hard spheres, which does not assume any specific features of a short-range order, is considered. The results obtained allow (in particular) us to determine the maximum possible density of a random packing, which has no any types of explicit or hidden long-range order. New computer experiment data, which describe the statistical–geometrical properties of random packings of two-dimensional (2D) and three-dimensional (3D) hard spherical particles, are presented. The behavior of a small group of randomly chosen and fixed spheres at various packing densities and the differences between the properties of this group and the main "large" ensemble (which follow, in particular, from the theoretical results obtained) are investigated. The dependences found experimentally are consistent with the proposed theoretical solution. Let an ensemble consist of N particles occupying total volume V (at packing density η = Nu/V, where u is the particle volume). The maximum possible density of a random packing of spherical particles (ηmax) is specified by the following geometric condition: the average volume of a Voronoi polyhedron in a random close packing cannot be smaller than the average excluded volume for all points of this packing. For an arbitrary point of the ensemble lying at a distance x from the nearest center of sphere (unit radius R = 1), excluded volume w is determined by the following relations. In 2D space, we have w(x) = π(2 – x)2 at 0 ≤ x ≤ 2 and w(x) = 0 at x > 2. In 3D space, we have w(x) = (4π/3)(2 – x)3 at 0 ≤ x ≤ 2 and w(x) = 0 at x > 2. Averaging w(x) for all points of the volume of an ensemble of particles, we can find average excluded volume 〈w〉 for a given packing density η. We can also formulate the following statement, which follows from the condition given above: if packing density η exceeds ηmax, this packing cannot be statistically homogeneous. The approach used in this work can be used to calculate the maximum possible density (upper limit) of a random close packing. This density is ηmax = 0.6813 ± 0.001 (in 2D case of an ensemble of hard disks) and ηmax = 0.6329 ± 0.0005 (for a 3D ensemble of hard spheres). [ABSTRACT FROM AUTHOR]

Abstract—NbC–WC–Cu composite alloys are fabricated at 1300°C by impregnating mixtures of compacted and noncompacted carbide powders with the copper melt under low-frequency (80 Hz) vibration. Under these conditions, carbides are shown to interact with the formation of core (NbC)–shell ((W,Nb)C) solid solution) structures in the copper melt. The formation of a (W,Nb)C solid solution on the surface of NbC particles promotes the wetting of the carbide with copper. The thermal stability of the carbide solid solutions is investigated during isothermal holding at 500 and 1000°C for 60 min and during slow (10 K/min) heating to 1300°C. A reversible decomposition is detected, and the boundaries of low-temperature latent decomposition of the (Nb,W)C solid solutions are determined by the mass ratio of monocarbides NbC : WC in their alloy with copper. The higher the ratio, the lower the (Nb,W)C decomposition temperature. [ABSTRACT FROM AUTHOR]

The conditions of the formation of stable and metastable aluminides Aln(Zr1 – xNbx) formed during the crystallization of superheated melts of the Al‒Zr‒Nb system are considered. Upon a close zirconium content in the alloys of 0.23–0.25 at %, the niobium content varies from 0.05 to 0.21 at %. Alloys are prepared in a resistance furnace at a temperature of 1230°C in an argon atmosphere in graphite crucibles. The alloys are cast into a bronze mold; the cooling rate is estimated as 200°C/s. The structural features, distribution, and morphology; the composition of matrix, dendritic cells, and aluminides; and the structural type of aluminides in the alloys are studied using scanning electron and optical microscopy, X-ray diffraction, and inductively coupled plasma atomic emission spectroscopy. It is shown that the growth forms of stable aluminides (D023 structural type) change from faceted to dendritic and primary metastable aluminides (L12 structural type) begin to form; in the process of the Al‒Zr‒Nb melt, overheating was 360–365°C above the liquidus temperature. Exclusively metastable aluminides with both polyhedral and dendritic growth forms are formed in the Al‒Zr‒Nb alloys when the overheating of their melt is 390–395°C (as well as at higher overheating) above the liquidus temperature. The near-peritectic niobium composition of the Al‒Zr‒Nb alloy and the zirconium content (more than seven times higher than peritectic) are crucial factors in the formation of a large fraction of metastable AlnZr aluminides having a cubic L12 structure. It is shown that, in accordance with the rules of isomorphism, Nb replaces Zr at equivalent positions of the aluminides crystal lattice. The intensity of isomorphism of the formed Al4(Zr0.79Nb0.21) aluminides increases with the increase in temperature of the melt overheating. [ABSTRACT FROM AUTHOR]

Prototypes of high-current electrical contacts W70Cu30 with a frameless packing of dispersed W particles were obtained using precrystallization low-frequency vibration of the compositions "copper melt–uncompacted powder W." Samples were tested for arc resistance in air in a laboratory device that simulates the operation of an AC contactor. Analysis of the structure (before and after 10 000 arc discharge times) and functional properties (transitional contact resistance and hardness) of the obtained alloys in comparison with industrial contacts W70D30-MP was carried out. It is shown that the difference in the structures of the initial alloys is in the nature of the distribution and size of inclusions of the tungsten phase. In the industrial alloy, tungsten forms a continuous framework of large monolithic formations oriented parallel to the working surface. Their thickness is in the range of 10–100 μm, and length reaches 500 μm. In the experimental alloy, the tungsten phase is represented by dispersed particles with size of 1–3 μm, separated by copper. After repeated arc discharges, these microparticles do not cure and do not form a continuous frame even in the uppermost working layers of the contacts. In the industrial alloy, under the action of the arc, both the dispersion of the framework into individual large particles of tungsten (up to 60 μm) and their subsequent merger occur simultaneously, which leads to an increase in the relief of the working surface. The values of transitional contact resistance up to 6000 arc discharge times in both alloys have similar extents. After that, there is a tendency to a more intense increase in transition resistance in the industrial alloy. Despite the fact that the hardness of the frameless alloy is lower than that of industrial alloy, its undoubted advantages are in dispersion and dimensional stability of inclusions of the hardening tungsten phase under the action of high temperatures (in the arc plasma). [ABSTRACT FROM AUTHOR]

Composite Cu–Cr–N alloys were obtained in situ under vibration of "copper melt–chromium powder" compositions before their crystallization. Two types of alloys were prepared, where chromium powder was freely dispersed or compacted into a tablet. Atmospheric nitrogen was used as a source of chromium nitrides in the alloys. The microstructure of the alloys is represented by a copper matrix hardened with chromium particles and numerous inclusions of nonstoichiometric chromium nitrides Cr2N1 –x. Thermodynamic modeling showed that the composition and quantities of chromium nitrides in the Cu–Cr–N alloy depend on the partial pressure of nitrogen above the melt. [ABSTRACT FROM AUTHOR]

Cu–(20 wt %)Cr alloys with a layered structure are synthesized by liquid phase impregnation of chromium powder with copper melt. In synthesizing the alloys, the corresponding composites are subjected to pre-crystallization vibrational treatment. The layers of composites are enriched in chromium to different extents (from ~2 to 90 vol %). The layer composition and structure are shown to depend on the temperature and duration of vibrational treatment, as well as on the degree of pre-synthesis compaction of chromium powder. We study the phase composition of prepared alloys, the element composition of phases, and their microhardness. Our experiments show for the first time the formation of Cr core–(Cr + Cu) shell structures on the basis of chromium particles. These structures have a gradient distribution of the elements in the shell and form at the initial stages of interaction between Cu and Cr. At advanced stages of interaction, chromium particles are permeated with copper completely. In electron microscopy images in backscattered electrons, these formations appear as being greatly blurred and shapeless. In this way, precursors to crystallization of chromium dendrites are formed. The dendrite crystallization takes place in upper layers of the melt provided copper is present at the necessary and sufficient concentration (or at considerable superheating). The morphology of dendrites in which crystallization from precursors was incomplete is studied. The contact area of α-Cu is anticipated to be greatly reduced by the precursors that spread in the copper matrix during arcing. At the same time, contact welding will be considerably reduced, compared to similar composites with purely copper matrices (e.g., Cu–W). [ABSTRACT FROM AUTHOR]

The conditions of formation of metastable Zr or Ti aluminides with Y under crystallization of superheated melts of the Al – Zr – Y and Al – Ti – Y systems with hypoeutectic and hypereutectic compositions with respect to yttrium are studied. Complex Al3(Zr0.67Y0.33) and Aln(Ti0.67Y0.33) aluminides with cubic lattices are shown to form due to crystallization of the Al – Zr – Y and Al – Ti – Y melts hypereutectic with respect to yttrium after superheating by 300°C above the liquidus temperatures. [ABSTRACT FROM AUTHOR]

Vanadium-based alloys with a BCC structure are considered to be an alternative to palladium alloys for hydrogen purification. Since the performance of membranes is influenced by not only their bulk characteristics but also their surface condition, we have investigated the effect of different surface preparation techniques (abrasive grinding and polishing, electrolytic polishing, and ion etching) on the surface microstructure of V85Ni15 membrane alloy using X-ray photoelectron spectroscopy. After electrolytic polishing and ion etching, we observed an increase in the percentages of vanadium and nickel metals in the surface layer of the alloy in comparison with its state after abrasive polishing. Such changes are expected to be favorable for an increase in the rate of hydrogen dissociation and recombination on the surface of the membrane material, eventually improving hydrogen transport efficiency. [ABSTRACT FROM AUTHOR]

A technique for production of high-density composite material (Cu-1 wt % Al2O3) by single-fold cold compacting and sintering was developed. It is known that presence of gases in ductile metals, e.g., copper, inhibits consolidation of powder metal products. The technique is able to succeed in degassing of the composite material during heating in a hydrogen atmosphere. The technique is based on addition of cobalt and copper oxalates in a mixture of Cu and Al2O3. The efficiency of the technique was estimated by the relative density and hardness values of produced Cu-Al2O3 composite materials. The mechanism of impact of activated sintering on compaction of composite materials was investigated. It was found that decomposition of cobalt and copper oxalates at heating in hydrogen atmosphere synchronizes activated reduction of copper oxides and degassing of products, supporting permeability of composite materials. Composition of active admixture 0.5 wt % CoC2O4 + (2-2.5) wt % CuC2O4 is optimized. It was found experimentally that addition of oxalates produces a positive impact on consolidation processes and properties of composite materials on the basis of copper and Al2O3 micro- and nanoparticles irrespective of preparation techniques: electrolysis, evaporation-condensation, salt decomposition, precipitation and coprecipitation of hydroxides with further reducing heat treatment and milling. Application of activated sintering of powders obtained by coprecipitation of hydroxides and compacted at 700 MPa enables the formation of Cu-1% Al2O3 composite material with improved properties. As a result, composite material with homogeneous structure (grain size of 2-10 μm), increased values of density (8.4 g/cm3), and Brinell hardness up to 780 MPa was produced. [ABSTRACT FROM AUTHOR]

Ternary master alloys Al-Sc-Zr, Al-Sc-Ti, and Al-Ti-Zr are prepared. The complex aluminides Al 3(Sc xZr 1−x), Al 3(Sc xTi 1−x), and Al 3(Ti xZr 1−x) in them have the L1 2 cubic lattice, which ensures high structural and size matching with the crystal lattice of the matrix of the aluminum alloys modified by these master alloys. The action of low-frequency vibrations on the melts of the ternary master alloys favors the fragmentation of the aluminides down to sizes smaller than 10–30 μm and their uniform distribution in an alloy matrix. [ABSTRACT FROM AUTHOR]