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The paper presents the results of a study of the microstructure, elemental and phase compositions of the eutectic alloy (wt %): Al–12.5 Si–0.8 Mg–0.4 Mn–0.7 Fe–0.9 Ni–1.8 Cu. A comparison of the microstructure of the alloy obtained at melt cooling rates of 102 and 105 K/s is made. It is shown that an increase in the melt cooling rate leads to the refinement of structural components, a decrease in the volume fraction of primary α-Al dendrites, an increase in the volume fraction of a mixture of eutectic silicon and aluminum, and a decrease in the silicon concentration in the interdendritic space from 23 to 13 wt %. Using energy-dispersive analysis and X-ray diffraction analysis, it was revealed that inclusions of intermetallic compounds Mg5Si6, Al17(FeMn)Si2, and Al3(CuNi)2 are formed at melt cooling rates of 102 and 105 K/s. A mechanism of the formation of a layered microstructure of an eutectic alloy is proposed. An explanation for the formation of X-ray amorphous nanosized particles in the foil layer adjacent to the mold is given. [ABSTRACT FROM AUTHOR]

The structural and phase state of the surface layers of Al, Al-Si, and Al-Si-Cu-Mg alloys doped with zirconium atoms under the influence of compression plasma flows is studied. It is established that metastable compounds Al3Zr with the crystal structure L12 and (Al, Si)3Zr with the structure D022 are formed in the doped layers of aluminum and silumins, respectively. It is shown that doping of the studied alloys with zirconium makes it possible to increase the microhardness of the surface layer by 1.4–3 times. A study of the thermal stability of the structural and phase state of the doped layers at 550°C showed that, as a result of aluminum annealing, the Al3Zr phase with the L12 structure transforms into the Al3Zr compound with the D023 structure, and in the alloys of the Al–Si system, the decomposition of (Al,Si)3Zr and the formation of ZrSi2 occur. It is noted that the synthesized surface layer has increased temperature strength. [ABSTRACT FROM AUTHOR]

Aluminium whose Silicon as its main alloying element, i. e. Silumin, is widely applied in engineering due to its novel properties. For particular application, e. g. as block engine of seawater vessel, Silumin's properties must be enhanced, e. g. strength at elevated temperature, hardenability and corrosion resistance. For those purposes, Nickel and Copper is added to Silumin in this work. As a result, Copper addition by 4.1 % wt increases Silumin density by 13.9 % from 2.95 to 3.36 g/cm³, decreases grain size by 35.3 % from 39.4 to 25.5 μm, increases hardness by 178.8 % from 21.66 to 60.38 HR30T and increases the corrosion rate by 24.5 % from 0.354 to 0.441 mmpy. Meanwhile, addition of Nickel by 6.35 % wt increases Silumin density by 14.9 % from 2.95 to 3.39 g/cm³, decreases grain size by 29.7 % from 39.4 to 27.7 μm, increases hardness by 161.8 % from 21.66 to 56.71 HR30T and decreases the corrosion rate by 41.2 % from 0.354 to 0.2211 mmpy. To investigate the influence of Copper and Nickel addition on Silumin's microstructure, micrograph is also taken by using an optical microscope and a scanning electron microscope. The micrograph shows dendrite presence only for the case of Copper added Silumin which deleterious for mechanical properties of Silumin. This dendrite is predicted due to slower cooling rate of the cast Silumin after Copper addition. In addition, the needle-like β-precipitate is sharper after Copper addition. This circumstance is responsible for higher hardness increase for the case of Copper addition compared to Nickel addition. The micrograph shows the existence of CuAl2 intermetallic phase. This intermetallic phase is nobler than Aluminium which is responsible for higher galvanic corrosion in Silumin after Copper addition. On the other hand, the dendrite cannot be observed in the case of Silumin after Nickel addition. The intermetallic phases after Nickel addition, i. e. AlxNiy contribute to the hardness increase. These phases also remain stable at elevated temperature which then then contributes to better mechanical properties of Silumin at the elevated temperature. [ABSTRACT FROM AUTHOR]

Unmodified hypoeutectic silumins have a microstructure composed of large-sized phases, which are the reason for their low mechanical properties. Many years of research have shown the modifying effects of many chemical elements and their compounds, including the master alloy consisting of Al-Ti-B, often in the form of the finished AlTi5B alloy. In this work, it was decided to check how the proportions of Ti and B content in the Al or AlSi-based master alloy affect the microstructure and mechanical properties of a hypoeutectic silumin, AlSi7Mg. It has been shown that a master alloy containing silicon (with the participation of Al + Ti + B) has a more effective impact on the refinement of the microstructure, and thus an increase in the mechanical properties of the AlSi7Mg alloy, than a master alloy without silicon. It has been shown that the ratio of titanium to boron content in the very-often-used AlTi5B modifier is not always optimal. It has been shown that the use of a master alloy with a composition similar to that of modified silumin with titanium and boron in a 2:1 ratio allows the obtaining of an AlSi7Mg alloy with higher mechanical properties than the alloy after the modification of the AlTi5 master alloy. [ABSTRACT FROM AUTHOR]

The paper deals with the possibilities of influencing the final microstructure of aluminium alloy castings by changing the external conditions of crystallization and solidification. Aluminum alloys, especially Al-Si alloys, are nowadays one of the most used non-ferrous metal alloys, especially due to their mass application in the automotive field. It is in this industry that extreme emphasis is placed on the quality of cast parts with regard to safety. For this reason, a key production parameter is the mastery of the control of the resulting microstructure of the castings and the associated internal quality, which is subject to high demands defined by international standards. The aim of the experiment of this paper is to evaluate the effect of different preheating of the metal mould on the resulting structure and hardness of test castings made of AlSi7Mg0.3 material. The hardness measurement will be evaluated on a hardness tester. The parameter SDAS, Microporosity, Content of excluded eutectic will be evaluated. Dependencies will be found and plotted.

It has been shown that the elementary crystal cells of the basic products of modification of silumins, aluminum and silicon do not correspond to the principle of structural and dimensional correspondence of Dankov – Konobeevsky. Modifying elements B, Sr, P significantly increase the surface energy of liquid silumins, and Zr and Ti practically do not affect it. Modification of silumins is a nanostructured process. Ti, Zr, B form intermetallides that refine aluminum nanocrystals from demodifying adsorbed hydrogen atoms. Phosphorus, atomically dissolving in silumin, refiners silicon nanocrystals from adsorbed oxygen. Na and Sr form an emulsion and colloid in liquid silumin, which protect eutectic microcrystals of α‑and βSi‑phases from demodifying molecular hydrogen. All these processes increase the concentration of crystallization centers of dendritic microcrystals α‑and βSi‑phase, make them more branched and compact.

Oxide layers formed by plasma-electrolytic oxidation (PEO) are characterized by a sufficiently high porosity, which influences almost the whole complex of service characteristics. However, the known data on the integral porosity of PEO-produced layers are rather contradictory, and the pore size distribution in these layers remains understudied. Pore size distribution in the range of 10 nm to 10 µm (pore geometry was approximated by a spherical shape) was obtained by using analysis of scanning electron microscopy (SEM) images in a wide range of magnifications. Lognormal distribution function fits the shape of pore size distribution sufficiently well. Such distribution indicates the nature of pore formation, which can be related to the thermally activated process of gas emission from a liquid melt, the volume and average temperature of which, in turn, depend on the micro-arc discharge energy. The results of the oxide layer phase composition and crystallites sizes by the X-ray crystallography were described in the present paper. The amorphous component phase composition was estimated by the comparing of the of X-ray spectral microanalysis and X-ray crystallography methods. The thermal conductivity of the intact oxide layer and the polished layer (after the removal of its highly-porous outer part) was evaluated by using of the steady-state method and the laser flash method. The porosity values calculated based on the analysis of SEM-images, and the results of determining the phase composition, including amorphous phases, allowed evaluating the oxide layer thermal conductivity with use of four known analytical models. The results of calculating the thermal conductivity using the Loeb model demonstrate the good convergence with the experimental results obtained in this paper. Modeling results the size of crystallites effect on the oxide layer thermal conductivity significantly less than the porosity and amorphous phase.

Using mathematical three-dimensional modeling methods, the features of the distribution of electric and thermal fields within the volume of the melt of the casting alloy A356 have been established during its treatment with electric current using parallel electrodes. It has been found that the geometry of the electrode system qualitatively and quantitatively determines the effect of electrothermal action on the melt during treatment with direct current. It has been shown that the depth of immersion of electrodes with an uninsulated lateral surface does not have an active influence on temperature processes during conductive electrocurrent treatment. The qualitative and quantitative data obtained for systems with uninsulated electrodes correspond to the results of experimental studies. It has been shown that changing the spatial geometry of the arrangement of electrodes with insulated lateral surfaces significantly affects the spatial distribution of electric and thermal fields, resulting in a more than threefold quantitative change in the characteristics of these fields within the melt volume. The method for controlling the processes of conductive electrothermal treatment of melts based on spatial changes in the type of electrode system does not require additional costs and can be carried out directly during the treatment process. [ABSTRACT FROM AUTHOR]

The influence of various modifying additives on the shrinkage porosity of silumins and the tightness of castings is considered. A comparative assessment of the modification of the shrinkage components in the resulting blanks was carried out. The dependences of the strontium content in the silumin melt depending on the melt holding time are established. The relationship between the level of scrap of aluminum castings and the content of strontium has been revealed. Due to the fact that the level of rejection of aluminum castings due to leakiness does not directly depend on the porosity in the alloy, it is suggested that strontium has significant changes in the mechanism of crystallization of the alloy and the distribution of microporosity in the alloy structure with the formation of a more developed channels.

Crystal structure of oxide ceramic coatings obtained on AK9M2 and AK12 alloys is determined. Already after 5 min of processing the AK9M2 alloy by plasma electrolyte oxidation (PEO) method in a standard electrolyte (KOH (3 g/L), Na 2SiO3 (2 g/L)), aluminum and silicon form a compound Al3.21Si0.47. The thermal stability of compounds with the Al2O3∙SiO2 composition is analyzed. A scheme for converting intermediate oxides into mullite is proposed. The obtained results show that with the increase of silicon content in alloys the amount of sillimanite in the corresponding coatings increases. Increase of the PEO process of silumins processing to 2 h causes a partial transformation of sillimanite into mullite. The maximum content of mullite in coatings is approximately 4 mass%. [ABSTRACT FROM AUTHOR]

The paper deals with the possibilities of influencing the final microstructure of aluminium alloy castings by changing the external conditions of crystallization and solidification. Aluminum alloys, especially Al-Si alloys, are nowadays one of the most used non-ferrous metal alloys, especially due to their mass application in the automotive field. It is in this industry that extreme emphasis is placed on the quality of cast parts with regard to safety. For this reason, a key production parameter is the mastery of the control of the resulting microstructure of the castings and the associated internal quality, which is subject to high demands defined by international standards. The aim of the experiment of this paper is to evaluate the effect of different preheating of the metal mould on the resulting structure and hardness of test castings made of AlSi7Mg0.3 material. The hardness measurement will be evaluated on a hardness tester. The parameter SDAS, Microporosity, Content of excluded eutectic will be evaluated. Dependencies will be found and plotted. [ABSTRACT FROM AUTHOR]

Unmodified hypoeutectic silumins have a microstructure composed of large-sized phases, which are the reason for their low mechanical properties. Many years of research have shown the modifying effects of many chemical elements and their compounds, including the master alloy consisting of Al-Ti-B, often in the form of the finished AlTi5B alloy. In this work, it was decided to check how the proportions of Ti and B content in the Al or AlSi-based master alloy affect the microstructure and mechanical properties of a hypoeutectic silumin, AlSi7Mg. It has been shown that a master alloy containing silicon (with the participation of Al + Ti + B) has a more effective impact on the refinement of the microstructure, and thus an increase in the mechanical properties of the AlSi7Mg alloy, than a master alloy without silicon. It has been shown that the ratio of titanium to boron content in the very-often-used AlTi5B modifier is not always optimal. It has been shown that the use of a master alloy with a composition similar to that of modified silumin with titanium and boron in a 2:1 ratio allows the obtaining of an AlSi7Mg alloy with higher mechanical properties than the alloy after the modification of the AlTi5 master alloy.

The article deals with the possibility of influencing the properties of aluminium alloy castings by changing the external conditions during solidification. Due to the high demands of customers, influencing the resulting microstructure is an important process in the production of castings. When casting an aluminium alloy into a metal mould, the mould must be preheated to a high temperature. For this reason, the key parameter of production is the mastery of the control of the resulting microstructure of castings and the related internal quality and mechanical properties, which are subject to high demands defined by international standards.The aim of the experiment is to evaluate the influence of different preheating of the metal mould on the resulting structure of test castings made of AlSi10Mg material and its subsequent thermal expansion. It is hypothesized that as the temperature of the mould preheating increases, the mechanical properties will deteriorate and the expansion of the alloy will increase. In the case of immediate use of castings after production, this could have a negative impact on the service life and safety of entire assembled components. All measured results will be put into comparison and direct connections between the data will be searched using the microsoft excel program.

Silumins are advantageous antifriction alloys to produce friction units. However, owing to their low hardness and strength, there is a call for developing modifying and strengthening additives for them. Here, we prepare aluminosilicate–nickel (AS/Ni) composites by mechanochemical synthesis and propose them as the additives. Using Fourier transform infrared spectroscopy and X-ray diffraction, we investigate the structural changes in (1) powder mixtures of natural aluminosilicates and nickel subjected to high-energy mechanical processing in a planetary ball mill and (2) silumin–potassium tetrafluoroborate (KBF4) and silumin–KBF4–AS/Ni alloys prepared by hot pressing of the mechanically activated powders. Mechanical activation of the silumin–KBF4 powder mixture is shown to result in redistribution of silicon to form coarse primary silicon crystals in sintered material and a ~20% decrease in its microhardness. Mechanical activation of the aluminosilicates and nickel produces composite powders in which OH groups are removed and SiO2 framework units are formed. With this type of modifier used in sintering of silumin, the resulting alloy acquires a homogeneous finely dispersed structure with smaller eutectic particles and primary silicon grains, which improves the microhardness of alloy by a factor of 1.5. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Processing of Materials / Elektronnaya Obrabotka Materialov is the property of Institute of Applied Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study reports on the electron-beam processing (energy of accelerated electrons 17 keV, electron beam energy density ES = 10, 20, 30, 40, and 50 J/cm2, pulse duration 50 and 200 μs) of Al-10wt%Si-2wt%Cu alloy (silumin) surface. The important outcome to emerge from the study is a correlation between surface microhardness and electron beam energy density. As revealed, a maximal microhardness value is at ES = (30–40) J/cm2, being more than 1.6 times higher than the characteristic of the untreated material. The research has pointed out the electron-beam processing of silumin at ES = 10 J/cm2 causes the intensive destruction and microcracking along grain boundaries with particles of intermetallic compounds, as well as the globularization of cementite lamellae in eutectics. The irradiation of silumin by an electron beam (ES = 30–50 J/cm2) is shown to bring about the origination of micropores in the surface of samples, the dissolution of silicon, the globularization of intermetallic inclusions; in addition, a sub-micro-sized crystal structure of high-speed cellular crystallization forms. Finally, the electron-beam processing of silumin leads to the saturation of Al-based crystal lattice with alloying and impurity elements.

The article investigates the possibility of replacing the AlSi7Mg0.3 alloy used for manufacturing automotive wheel disks with eutectic silumin alloyed with magnesium. The crystal lattice constant, structure, hardness and mechanical properties of eutectic and hypoeutectic silumins have been determined, and their comparative analysis has been performed. It is shown that the heat hardenable eutectic silumin can be used for manufacturing cast automotive wheel disks instead of a less adaptable to manufacture AlSi7Mg0.3 alloy. [ABSTRACT FROM AUTHOR]

Barothermal treatment of the cast binary alloy Al–8 at % Si has been performed at 560°C/100 MPa/3 h. A microstructure with silicon particles with an average equivalent diameter of ~2.9 microns has been formed in the alloy. Barothermically treated silumin had a yield stress of 67.6 MPa, a tensile strength of 141.6 MPa, and a relative elongation of 34.1%. Cold deformation of the alloy to obtain a foil with a thickness of 16 microns has been realized. A decrease of the aluminum and silicon crystal lattice constants has been established, which is more noticeable at the maximum deformation of the alloy. When deformed, a textured alloy structure is formed with an axis of {100} along the rolling direction. The mechanical properties of the deformed alloy are determined, and the values of yield stress, tensile strength, and elongation equal to ~265 MPa, 305 MPa, and 5.5%, respectively, are obtained for a tape with a thickness of 900 microns. With a higher degree of deformation, for a tape with a thickness of 90 microns, these characteristics have values of ~146 MPa, 165 MPa and 1.4%, respectively, and for the foil with a thickness of 16 microns, ~180 MPa, 196 MPa and 0.3%, respectively. [ABSTRACT FROM AUTHOR]

It is shown that the main technological problems of modifying of structure of silumin castings are: absence of the universal modifiers, limitation of their action in time; saturation of a melt by hydrogen and oxide of silicon. Admixture modifiers do not solve these problems. These problems could be solved by method of hereditary modifying. For this purpose it is necessary to use the silumin castings with a high-dispersible microstructure received by casting in a crystallizer with a high speed of cooling.

It is shown that intermetallic metals of the modifying ligatures are not the crystallization centers of primary crystals of a a-phase. As the main demodifier serves hydrogen dissolved in liquid silumin. For a solution of the problem of modifying of primary crystals of a a-phase in castings from silumins it is necessary to accept a presumption that crystallization centers of primary crystals of a a-phase are the crystalline developments consisting of a-phase nanocrystals, and the role of the modifying intermetallic metals of modifiers comes down to the active absorption of the dissolved hydrogen.

Using methods of physical material studies (scanning electron microscopy and micro X-ray spectral analysis), a study was carried out with focus on alteration of structure and phase composition in surface layers of Al-Si alloy (silumin АК10М2N) treated in electroexplosive alloying with a multiphase plasma jet formed in the process of aluminum foil explosion and carrying particles of Y2O3 weighted powder portion. It was revealed that a porous surface layer with non-homogeneously distributed alloying elements (silicon, yttrium) in it is formed in any conditions of electroexplosive alloying of silumin. Thickness of the modified layer is different, varying 50 to 160 µm, depending on the zone to be examined. The modified surface consists basically of Al, Si and Y. Yttrium in the modified layer is thought to be an indirect evidence of better physical and mechanical properties of the surface layer in comparison with the base material.

It is shown that modern industrial modifiers of silumin eutectic contribute to the saturation of the melt with hydrogen. Its micro bubbles block the branching of eutectic crystals and promote the formation of gas porosity in castings.To improve the efficiency of the process of modifying the eutectic and reduce the gas porosity, a method of hereditary modification is proposed. A special technology has been developed to solve the problem of modification of silumin eutectic.

On the paper the influence of modifying micro additives on the refinement of primary silicon crystals in the hypereutectic AlSi21CuNi piston silumin have been examined. As the modifiers there were used micro additives of Phosphorus in the form of AlCu19P1.4 and CuP12 pre-alloys, sulfur in the form of CuS and iron in the powdered form. The modifying micro additives were used separately and together. Micro additions of iron were used together with phosphorus. Sulfur micro addition provided the fragmentation of the primary silicon crystals, but not as effective as the phosphorus micro additive. The best effect of fragmentation of the primary silicon crystals was ensured by the combined addition of phosphorus in the form of AlCu19P1,4 pre alloy with a micro additive of powdered iron which reduced the average size of the primary silicon crystals from 114 μm to 20 μm.

It is shown that the phosphorum which is contained in a silumin melt in number of 0,01–0,04% exists in the dissolved form. For a solution of the problem of modifying of primary crystals of a β -phase in silumin castings it is necessary to accept a presumption that the oxygen adsorbed by a melt promotes decay and hinders the formation of crystallization centers of primary crystals of a β -phase. The role of phosphorum comes down to reduction of concentration of the adsorbed oxygen which works as the demodifier of primary microstructure of castings.

There has been growing interest in studying the formation of the structure and properties of aluminum alloys in a solid-liquid state, which is practically not used in domestic metallurgy and mechanical engineering, those at temperatures slightly higher than the eutectic, which leads to a change in the eutectic structure of the acicular type to a more dispersed equiaxial one. Therefore, the purpose of this work is to study structure formation during thixotropic treatment of an aluminum-silicon alloy, which takes place with the participation of a liquid phase, the modes of which can be adapted for thixotropic casting, which will allow changing the shape and size of eutectic crystals, which ultimately affects the mechanical properties of products. In the course of the work, the Al-12%Si alloy was studied, which underwent heat treatment at temperatures from 572 to 600 °C. During heating, isothermal holding, and cooling at a temperature above the eutectic temperature, melting and recrystallization processes occur in parallel. It was found that since the change in the state of the system is determined by a decrease in the thermodynamic potential (Gibbs energy), it is necessary to take into account the change in the volumetric energy and the change in the surface energy associated with melting (the appearance of new melt/α-solid solution and melt/Si interfaces). But it is also important to take into account that during isothermal exposure, the total surface energy will change in such a way as to minimize the final surface energy. [ABSTRACT FROM AUTHOR]

The surface of AK5M2 (Al–Si) alloy is treated with an intense pulsed electron beam in various modes (accelerated electron energy of 17 keV, electron-beam energy density of 10, 20, 30, 40 and 50 J/cm2, pulse duration of 50 and 200 μs, the number of pulses 3, and the pulse repetition rate 0.3 s–1). Microhardness analysis is performed, and the elemental and phase composition and state of the defect substructure of the surface layer are studied by scanning electron microscopy and X-ray phase analysis. It is shown that the increase in microhardness of the Al-Si alloy is due to the formation of a submicrometer-sized structure of high-speed cellular crystallization, the enrichment of an aluminum-based solid solution with alloying and impurity elements, and the reprecipitation of nanoscale particles of strengthening phases. It is suggested that the higher values of the microhardness found in the alloy irradiated at 50 J/cm2 and 50 μs compared with the alloy irradiated at 50 J/cm2 and 200 μs are due to the process of tempering the material, which have a greater development with a longer duration of exposure to beam electrons per pulse. [ABSTRACT FROM AUTHOR]

In this article various technological schemes for processing waste in the form of chips of an alloy of an aluminum-silicon system are presented. It was noted that the processing of fine waste of the chips type is always accompanied by oxidation of the metal due to the large surface of contact with the air. To eliminate the loss of metal into oxides during re-melting, this study proposes processing chips by pressing to obtain briquettes (a method of hot extrusion is meant by 'pressing'). Processing involves the receipt of briquettes from rods. The processes of cold and hot briquetting were undertaken separately. The results of applying the scheme using real production waste are presented in this study. The tensile strength achieved was up to 270 MPa. The relative elongation to rupture was 10-25% and the area reduction after rupture was 25-45%. There were no large differences in the use of briquettes obtained by cold processing and hot processing. The conclusion is drawn about the overall effectiveness of the application of the waste processing without the use of the metal melting. [ABSTRACT FROM AUTHOR]

The microstructure, the phase composition, the component distribution, and the grain structure of the commercial eutectic Al–12.2 Si–0.2 Fe (at %) silumins formed at cooling rates of 102 and 105 K/s are studied. Three phases are detected in the alloy after solidification at both cooling rates: α-aluminum, silicon, and an iron-containing phase. The bulk samples have a heterogeneous dendritic structure with large dendrites of an aluminum-based solid solution, and a eutectic lamellar mixture of aluminum and silicon filling the interdendritic space. The melt-quenched foils are characterized by a homogeneous microstructure over the thickness; however, they have a layered structure. The rapidly solidified foils also have a homogeneous granular structure through the thickness and no pronounced texture. The mechanisms of solidification and microstructure formation are proposed for both the bulk samples and the melt-quenched foils. [ABSTRACT FROM AUTHOR]

The paper presents the results of modification of the silumin surface layer using a multicycle processing technique which combines the formation of the film (titanium)-substrate (silumin) system and the low energy high current pulsed electron beam (LEHCPEB) irradiation of submillisecond duration in one cycle. A KOMPLEX plasma-ion-assisted electron-beam setup (Institute of High Current Electronics SB RAS, Tomsk, Russia) is used for silumin treatment. Titanium is used as an alloying element. The thickness of the deposited film is 0.5 μm in each alloying cycle, the number of which is 1, 5 and 10. Surface alloying includes ion-bombardment cleaning and heating by hot and hollow cathodes of argon plasma discharge, with negative bias voltage supply to the specimen (initial heating up to preset temperature, surface cleaning and activation); plasma-enhanced chemical vapor deposition of metal films (argon is used as a carrier gas); and LEHCPEB irradiation of the film (titanium)-substrate (silumin) system. It is shown that multicycle alloying of the grade АK12 silumin (G-AlSi12, DIN, Germany) with titanium leads to a dissolution of silicon and intermetallic inclusions in the surface layer up to 30 μm thick, the formation of submicro- and nanocrystalline multiphase structure with the microhardness and wear resistance, which are 1.4 and 14.2 times higher than in cast silumin. [ABSTRACT FROM AUTHOR]

It is shown that at crystallization of alloys the sophisticated nanostructural processes have place. The nanocrystals of phases, their atoms, the centers of crystallization of dendrites, surface-active elements, gases, modifying elements, poorly soluble impurity elements generally participate in these processes. Their activity and intensity of abstraction of heat during crystallization define the structure of castings.

Methods of production of silumin with globular silicon are developed. The manufacturing of this new antifriction material are organized. The wear resistance and operational life of articles from silumin with globular silicon are on par with or surpass performance of similar articles of antifriction bronze, but the articles of silumin with globular silicon are lighter and three times cheaper than articles from antifriction bronze.

The work is a continuation of research concerning the influence of intensive cooling of permanent mold in order to increase the casting efficiency of aluminium alloys using the multipoint water mist cooling system. The paper presents results of investigation of crystallization process and microstructure of multicomponent synthetic hypereutectic alloy AlSi20CuNiCoMg. The study was conducted for unmodified silumin on the research station allowing the cooling of the special permanent sampler using a program of computer control. Furthermore, the study used a thermal imaging camera to analyze the solidification process of multicomponent alloy. The study demonstrated that the use of mold cooled with water mist stream allows in wide range to form the microstructure of hypereutectic multicomponent silumin. It leads to higher homogeneity of microstructure and refinement of crystallizing phases of casting.

The paper presents a research on the effect of extreme - for the technology of the considered silumin EN AB 47100 - parameters of high-pressure die casting on occurrence of casting nonconformities. Considered was influence of the way of assembling the mould cooled-down to 140-160°C, non-standard for the selected casting, and pouring temperature in the range of 705 to 720°C (higher than the recommended) of non-refined alloy. The castings were prepared with use of a high-pressure casting machine made by Kirov with mould closing force of 2500 kN. Occurrence of nonconformities was evaluated on properly prepared specimens taken from the castings manufactured with various parameters of the injection piston and various multiplication pressures. The results were subjected to quantitative and qualitative analyses of casting nonconformities and distribution of major alloying elements. It was found that proper selection of working parameters of the casting machine, in spite of disadvantageous pouring conditions, makes it possible to reduce occurrence of some casting defects, like shrinkage cavities and porosity, to improve tightness of castings even when the alloy refining process is omitted.

The structure and mechanical characteristics of alloy AK9ch are studied after different treatments involving homogenization and modification of the melt. The micromechanism of crack growth in alloy AK9ch after the treatments is investigated. The composition of the phases is studied quantitatively with plotting maps of the distribution of elements in them. The changes in the morphology of the individual phase components due to the modifying and due to joint homogenizing and modifying are determined. [ABSTRACT FROM AUTHOR]

The structure, phase composition and tribological properties of surface layers of hypoeutectic silumin after the complex processing including the electroexplosion alloying with the yttrium oxide powder in different regimes and the subsequent electron beam processing have been analyzed by the methods of modern physical material science. With respect to the initial silumin the ≈20-fold increase in the wear resistance and ≈1.5-fold decrease in the friction coefficient have been detected. The complex processing is accompanied by the formation of the multiphase submicro—nanocrystalline layer up to 80 μm in thickness enriched by yttrium and oxygen atoms responsible for the multiple increase in the wear resistance. At the complex processing according to the first regime of electroexplosion alloying (EEA) (Y2O3 powder mass—0.0589 g, discharge voltage—2.8 kV) with the subsequent electron beam irradiation, the major phase of the modified layer is the solid solution based on Al (≈71.2 mass %), the remaining phases are SiO2, YAlO3, YSi2. The 1.5-fold increase in the mass of Y2O3 powder at EEA and 1.1-fold decrease in the discharge voltage is accompanied by the increase in the quantity of phases, the significant (more than 2.5-fold) decrease in the content of the solid solution based on Al, the ≈2.2-fold increase in the content of silicon oxide, the presence of yttrium oxide and metallic yttrium. [ABSTRACT FROM AUTHOR]

The analysis of the gradient structure-phase states and nanohardness of hypoeutectoid silumin at 120 μm depth after the processing by high intensive electron beams in the regime of top layer melting has been carried out. It has been shown that depending on the depth to the surface of irradiation the electron beam processing leads to the dissolution of the primary inclusions of silicon and intermetallides and the formation of structure of high-speed cellular crystallization of aluminium and the grains of plastic eutectic. A 1.5‒2 fold decrease in the concentration of the alloying elements has been detected. The hardness of irradiated silumin changes in a nonmonotonous way and reaches the maximum values exceeding the hardness of the initial state by 3.8‒4.2 times in the layer located at 30–50 μm depth. The interpretation of the observed changes in structure and hardness on irradiation has been given. [ABSTRACT FROM AUTHOR]

• The strengthening of hypoeutectic silumin surface was performed by complex method. • The multiple increase in wear resistance of modified layer has been established. • The formation of multiphase submicro – nanodimentional states was revealed. The analysis of structure, phase composition and tribological properties of surface layers of hypoeutectic silumin after complex treatment including the electroexplosion alloying by yttrium oxide powder in different modes and subsequent electron beam processing was done by the methods of modern physical material science. The complex treatment is accompanied by the formation of multi–phase submicro – nanocrystalline layer up to 80 μm thick enriched by yttrium atoms and being responsible for the increase in wear resistance. It is shown that Y atom concentration in the modified layer depends on electroexplosion alloying (EEA) mode. The distribution of Y atoms in the layer depends on the mode of EEA as well. [ABSTRACT FROM AUTHOR]

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It is established that the electron-beam treatment of AK10M2N silumin by a pulsed electron beam with the specific energy of 35 J/cm2 leads to the increase in the surface layer microhardness from 0.99 up to 1.18 GPa with the simultaneous decrease in the friction coefficient by 1.3 times and in the wear coefficient by 6.6 times. After irradiation, a multilayer gradient structure is formed in the surface layer of the silumin. In the surface layer, there are no inclusions of the second phase, whereas in the deeper transient layer there are primary precipitations of intermetallic phase, which are the centers of aluminum crystallization. It is found that the changes in the mechanical and tribological properties of the silumin surface layers are associated with significant structural transformations, for instance, with the dissolution of silicon and intermetallics during irradiation of material with a high-intensity pulsed electron beam. [ABSTRACT FROM AUTHOR]

Using methods of physical material studies (scanning electron microscopy and micro X-ray spectral analysis), a study was carried out with focus on alteration of structure and phase composition in surface layers of Al-Si alloy (silumin AK10M2N) treated in electroexplosive alloying with a multiphase plasma jet formed in the process of aluminum foil explosion and carrying particles of Y2O3 weighted powder portion. It was revealed that a porous surface layer with non-homogeneously distributed alloying elements (silicon, yttrium) in it is formed in any conditions of electroexplosive alloying of silumin. Thickness of the modified layer is different, varying 50 to 160 μm, depending on the zone to be examined. The modified surface consists basically of Al, Si and Y. Yttrium in the modified layer is thought to be an indirect evidence of better physical and mechanical properties of the surface layer in comparison with the base material. [ABSTRACT FROM AUTHOR]

The microstructure of an unmodified AlSi9Mg alloy comprises large primary α phase dendrites, eutectic β phase crystals and eutectic α phase. This composition is responsible for the alloy’s low strength parameters, and it limits the extent of practical applications. The mechanical properties of hypoeutectic silumins can be improved through chemical modification as well as traditional or technological processing. Modification improves the mechanical properties of alloys through grain refinement. This study presents the results of double modification of an AlSi9Mg alloy with strontium, boron and titanium. The influence of the analyzed modifiers on the microstructure and mechanical properties of the processed alloy was presented in graphs. The modification of a hypoeutectic AlSi9Mg alloy improved the alloy’s properties. The results of the tests indicate that the mechanical properties of the modified alloy are determined by the sequence in which the components are introduced to the alloy.