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The development of modern high-tech industries of industrial production is impossible without the development of new methods for processing materials with high mechanical characteristics. There is a growing need for an increase in the proportion of parts made of aluminum alloys, a more complex configuration of cast parts, an increase in their reliability and durability in operation, etc. All this poses for metallurgists and foundry workers the task of creating new technologies for producing alloys, improving the technical and economic characteristics of structural materials, improving the quality and reducing the cost of castings.Hypoeutectic silumins have good casting properties, good weldability, machinability and corrosion resistance. However, they are prone to the formation of a coarse needle-like state, which reduces their useful characteristics. To eliminate this phenomenon, it is necessary to apply special technologies and the most common is their modification, which provides grain refinement. This makes it possible to use silumins for the manufacture of castings of complex shapes with increased density and low shrinkage porosity. Such parts can withstand average loads in critical units. Aluminum-silicon alloy AK7 or (ASi7Mg0.3) is a typical silumin, which is in demand in the automotive industry, construction, aircraft construction, machine, automobile and tractor production. It is appreciated for its good casting properties, weldability, machinability and corrosion resistance.

The results of structure and phase composition investigation in hypereutectic silumin alloy with 25 at. % Si content after high-energy pulsed compression plasma flows impact are presented in the work. The compression plasma flows impact with an absorbed energy density 25 – 40 J/cm2 allows to modify the sub-surface layer with a thickness up to 30 – 32 µm due to its melting and high rate solidification. By means of X-ray diffraction method, it was found the formation of two silicon phases with different grain sizes. The high-dispersed structure of silicon is presented in the Al-Si eutectic while the silicon phase with coarse grains exists in the primary crystals. The obtained results are the basis for a new method development for nanostructuring of the surface layers of hypereutectic silumin alloys increasing its wear resistance.

To improve functional properties of pre-eutectic silumins there are used many different methods having a complex effect upon processes of structure formation and physical-mechanical properties of alloys. In this paper there is offered a method for alloy operation characteristics increase by the example of wear-resistance by the impact of nanosecond electro-magnetic pulses (NEMP) upon silumin melt AK7ch (AL9). Melt illumination was carried out with the generator (NEMP) (GNI-01-1-6) submersible rod radiator. The melt was overheated to 900ºC and processed with NEMP with the length up to 25 min after that it was cooled at a rate of 20ºC/min. Slow cooling contributed to the formation of a structure close to equilibrium. Cylindrical ingots with a diameter of 0.06 m (60mm) and a height of 0.06 m (60 mm) were obtained. Wear-resistance was defined on a cross cut of ingots according to GOST 23.208-79. As a standard of comparison were used non-irradiated samples of silumin. It is defined that melt NEMP processing changes considerably parameters of crystallization, structure formation and increases silumin properties. At abrasive wear, silumin wear-resistance changes from the duration of melt electro-pulse processing according to an extreme dependence with the evident maximum at melt irradiation in the course of 15 min. At that in the edge area of the ingot wear-resistance increases by 1.54 times, and in the central one – by 1.34 times. This effect is explained by the fact that during melt NEMP processing during 15 min the characteristics of alloy micro-structure change considerably: morphology and dimensions of structural constituents. At that there is formed a qualitatively new fine structure of a non-dendritic type which ensures maximum values of alloy wear-resistance. The data obtained allow developing technology of wear-resistant silumin fusion intended for operation under abrasive wear conditions.

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.

The influence of the effect of combining different types of processing based on the physical force acting on the surface of conductive materials and the electrochemical active action of electrolytes acting as a cutting fluid is considered. The experiments carried out and show a significant effect of these types of processing on the surface quality and the provision of the initial various physical and mechanical properties of the processed materials. The article presents various dependencies of qualitative parameters for the implementation of shaping processes using such blade processing operations as turning, threading in holes of small diameter and expanding the holes. With combined processing methods, the process of forming the finish surface is due to the combined action of the cutting tool and the anodic dissolution of the metal under the influence of an electric current in the electrolyte solution. The application of this method allows obtain higher quality parameters when machining aluminum and copper alloys, the surface formed during processing, including the preservation of such special characteristics of certain materials, such as porosity.

To assess the effect of the mould filling modes on the content of oxide films in castings, special criterion is proposed that provides prediction in the contamination of chill castings mаde of aluminum alloys by using modern computing tools to simulate the moulds casting process on computer. It is noted that decrease in the value of the contamination criterion by using alloys with low content of Mg or without this component reduces the possibility of controlling the distribution of oxides in the casting, other elements of the casting mould and using the concentration of oxides, for example, in washers to control the mechanical properties of cast products. This is due to increase in the duration of oxidation processes in gas-tight mould with such change in the composition of the casting material.

In everyday life the use of vehicles has expanded immensely for some ventures and house hold applications, likewise the running time of engine cycle is exceptionally long. Thus because of the consistent running enormous measure of heat is produced. At the point when this heat isn't appropriately disseminated, the engine gets more fragile very soon and life of the engine declines because of the heat development. To build the life of the engine, heat dispersal is expanded by giving fins at external of engine chamber. The shape of the fins and the material used for the fin increases its heat dissipation capacity and in turn increases the cooling of the engine for proper functioning. The present work focuses on the design of fins of circular and tapered shapes for a 2-stroke engine. The temperature distribution and the heat dissipation along the fin surface of two shapes has been observed by a steady state thermal analysis. Alusil and Silumin has been selected as the fin materials and a computational evaluation has also been done using FEM. A better shape of the fin along with a suitable material has been selected based on the results observed by FEM and on comparison with the existing shape and material of the fin.

Effects of the high-energy compression plasma flows on the structure, elemental composition, and phase state of Al-44 at.% Si hypereutectic silumin alloy have been investigated. Using scanning electron and optical microscopy it was found decreasing in grain size of both primary silicon particles and Al-Si eutectic parts with increase of absorbed energy density of compression plasma flows. The primary silicon crystals were dispersed down to 300 nm in the result of high cooling rate of the melted layer after its homogenization by means of hydrodynamic mixing. It was found that increase in the absorbed energy density, homogenization of elemental composition in the modifies layer occurs due to increase in lifetime of the melted state and more efficiency mixing process.

A laser optoacoustic method for quantitative assessment of the volumetric porosity of cast dispersion-strengthened metal-matrix composite materials has been proposed and experimentally implemented. The method is based on a statistical analysis of the distribution of amplitudes of backscattered broadband pulses of longitudinal acoustic waves in the tested materials. Laser excitation and piezoelectric recording of ultrasound is implemented with one-way access to the test object using a special laser-ultrasonic transducer. Silumin-based composites reinforced with silicon carbide microparticles in various volume concentrations (0.033–0.135) and composites obtained by reaction injection moulding based on aluminum reinforced with intermetallic $${\text{A}}{{{\text{l}}}_{3}}{\text{Ti}}$$ (volume concentration 0.04–0.115) have been studied. For both types of composites, the distribution of amplitudes of backscattered ultrasonic signals is approximated by a Gaussian distribution function applicable for a large number of statistically independent quantities. The empirically obtained dependence of the half-width of this distribution on the volumetric porosity of composites of two different types is approximated by the same linear function regardless of the manufacturing technology, as well as of the type, size, and concentration of strengthening particles.

Силумин (сплав алюминия с кремнием) является дешевым промышленным сплавом, обладающим хорошей коррозионной стойкостью, высокими удельными механическими свойствами и хорошими литейными свойствами, вследствие чего нашел широкое применение в современной промышленности (авиа- и машиностроение, приборостроение, судостроение и т.д.). Целью настоящей работы является анализ закономерностей преобразования структуры и фазового состава поверхностного слоя силумина заэвтектического состава (Al - 22 вес. % Si ), подвергнутого облучению интенсивным импульсным электронным пучком. Установлено, что облучение силумина импульсным электронным пучком (18 кэВ, 25 Дж/см, 200 мкс, 3 имп., 0,3 с) приводит к плавлению поверхностного слоя толщиной до 60 мкм, высокоскоростная кристаллизация которого сопровождается формированием субмикро- нанокристаллической многофазной структуры. Показано, что алюминий (твердый раствор на основе ГЦК кристаллической решетки) формирует ячейки высокоскоростной кристаллизации; на границах ячеек расположены наноразмерные частицы вторых фаз. Выполнен анализ трехкомпонентных диаграмм состояния системы Al - Si - Fe - Cu (основные элементы исследуемого силумина) и продемонстрирована возможность формирования в сплаве в равновесных условиях большого количества двух- и трехэлементных соединений. Методами дифракционной электронной микроскопии показано, что наряду с трехэлементными фазами в силумине образуются и фазы на основе четырех и, возможно, большего количества элементов. Silumin (an alloy of aluminum with silicon) is a cheap industrial alloy with good corrosion resistance, high specific mechanical properties and good casting properties. As a result it has found wide applications in modern industry (aircraft and mechanical engineering, instrument making, shipbuilding, etc.). The aim of this work is to analyze the regularities of transformation of the structure and phase composition of the surface layer of a hypereutectic silumin (Al - 22 wt % Si), subjected to irradiation with an intense pulsed electron beam. It was found that irradiation of silumin with a pulsed electron beam (18 keV, 25 J / cm, 200 μs, 3 pulses, 0,3 s) leads to melting of the surface layer up to 60 pm thick, the high-speed crystallization of which is accompanied by the formation of a submicro-nanocrystalline multiphase structure. It is shown that aluminum (a solid solution based on fcc crystal lattice) forms cells of high-speed crystallization; nanoscale particles of the second phases are located at the cell boundaries. Analysis of three-component state diagrams of the Al - Si - Fe - Cu system (the main elements of the studied silumin) demonstrated the possibility of forming a large number of two- and three-element compounds in the alloy under equilibrium conditions. It has been shown by diffraction electron microscopy that, along with three-element phases, phases based on four and, possibly, more elements are formed in silumin.

Technologies for the 3D printing of metallic powders are being increasingly extensively used around the world as alternatives to casting and machining to manufacture components of complex shapes and prototypes. Silicon-alloyed aluminum alloys are the most widely used materials in the selective laser melting technologies, which is caused by the price of these alloys and their high manufacturability for the layer-by-layer fused deposition, owing to their low susceptibility to hot cracking under thermal and shrinkage stresses. High rates of cooling the melt facilitate the formation in the material of ultradispersed silicon-containing phases, which results in increased strength. In the article, exemplified by two cast alloys (AK7ch and AK9ch), the speeds of the process of building up the products by the selective laser melting technology have been determined at a laser-beam power of 300 and 325 W and an energy density within the range 89–32 J/mm3. It is shown that, for the AK9ch alloy, lower porosity values are achieved within the investigated energy density range when compared with the AK7ch alloy and better mechanical properties of the alloy with a higher silicon content are achieved within the range of lower laser-beam energy densities than for the alloy with a lower silicon content. The mechanical properties of the materials produced under the optimal selective laser melting conditions comply with the most stringent requirements for the mechanical characteristics of the castings of the AK7ch alloy upon heat treatment.

Aspects of increasing the strength of silumin due to the introduction of ultrafine silica powders into its melt are considered. The calculation of the surface energy of silicon oxide nanoparticles showed the promise of this modification. The method is proposed for increasing the adhesion of silicon to aluminum, due to the surface-active properties of magnesium and the high surface energy of nanoparticles, which contributes to the formation of chemical compounds of silicon with aluminum, and as a result, to hardening of the alloy. Due to the large difference in the surface energies of magnesium and silicon, the possibility of producing Si @ Mg core-shell nanoparticles in the one-step method under the action of an electron beam has been shown. The layout of substances in the graphite crucible, the dependence of the electron beam current to obtain Si @ Mg nanoparticles are presented.

Tribological tests of a hybrid composite (Al–12Si)–40Sn prepared by sintering mixtures of powders of silumin and pure tin were carried out using the pin-on-disk scheme. It has been established that an increase in the sliding velocity decreases the wear intensity of the composite upon dry friction, while an increase of the load leads to the opposite result. The data obtained indicate that the main contribution to the wear of the composite comes from the delamination of strongly deformed subsurface layers of the material. With an increase in the sliding velocity, the mechanism of the wear does not change, but, because of the heat-induced softening of the material, wear particles of the steel counterbody are pressed into it that “plate” the surface of the sample and reduce its wear intensity.

Явление структурной наследственности получило промышленное применение, несмотря на то что «механизм передачи наследственных признаков расплаву, их сохранение, зарождение в нем новых признаков и передача их твердому металлу - все это сложные, во многом неизученные вопросы» (Б.А. Баум с коллегами). На примерах стали, чугуна и алюминия предпринята попытка обоснования предположения, что одним из механизмов передачи наследственных признаков может быть эффект «памяти жидкости», который заключается в сохранении ее свойств при очень сильном разбавлении. The phenomenon of structural heredity is used by industry, although «the mechanism of transmission of hereditary traits to the melt, their conservation, the generation of new traits in it and their transfer to solid metal are all complex, largely unexplored issues» (B.A. Baum with colleagues). On the examples of steel, cast iron and aluminum, an attempt was made to substantiate the assumption that one of the mechanisms of transmission of hereditary traits could be the effect of «fluid memory», which consists in maintaining its properties with very strong dilution.

The decay mechanism of silicon particles in silumin in the thermal effect zone of low-energy high-current electron beam is proposed. Its essence consists in the fact that under the effect of the mechanical stresses the interface of silicon inclusion with aluminum matrix becomes instable resulting in the decay of silicon particle. It was supposed that the instability was the analog of Rayleigh-Taylor instability. The mechanical stresses arising due to the discrepancy of the elastic moduli and the linear expansion coefficients of the inclusion and the matrix are the analogs of gravity force. The analysis of the initial stage of instability within the frameworks of the visco-potential approximation has shown that the dependence of the rate of perturbations’ growth has only one maximum which falls on the wave length of the order ≈ 500 nm that is 5-fold higher than that of the experimental data. Such a discrepancy may be explained by the fact that when developing the model the temperature of the silicon inclusion and the aluminum matrix was considered to be constant, similar and being equal to the eutectic temperature of silumin. In fact, the temperatures of the inclusion and the matrix are different. To take into account the influence of these facts on the instability of the interface the new investigations are necessary.

In this paper we performed comparative studies of the tribological properties of the AlSi15Cu3 antifriction silumin and BrOTsS5-5-5, BrOF10-1, and BrAZh9-4 bronzes during friction in the I-20A lubricant environment in a wide range of sliding speeds and test pressures. It has been shown that no accumulation of defects occurs in the crystal lattice in its surface layers during the friction of an aluminum alloy. This is associated with the low recrystallization temperature of the aluminum matrix phase of the alloy. We conclude that AlSi15Cu3 antifriction silumin is a promising material for replacing expensive antifriction bronzes in highly loaded friction units.

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. Web of Science 8 11 art. no. e11363

This paper presents a study of a combined modification of silumin, which included deposition of a ZrN coating on a silumin substrate and subsequent treatment of the coating/substrate system with a submillisecond pulsed electron beam. The local temperature on the samples in the electron-beam-affected zone and the thickness of the melt zone were measured experimentally and calculated using a theoretical model. The Stefan problem was solved numerically for the fast heating of bare and ZrN-coated silumin under intense electron beam irradiation. Time variations of the temperature field, the position of the crystallization front, and the speed of the front movement have been calculated. It was found that when the coating thickness was increased from 0.5 to 2 μm, the surface temperature of the samples increased from 760 to 1070 °C, the rise rate of the surface temperature increased from 6 × 107 to 9 × 107 K/s, and the melt depth was no more than 57 μm. The speed of the melt front during the pulse was 3 × 105 µm/s. Good agreement was observed between the experimental and theoretical values of the temperature characteristics and melt zone thickness.

The process of mixed oxide coatings formation on a high-silicon aluminum alloy in a cobalt-containing pyrophosphate electrolyte by the plasma-electrolytic oxidation (PEO) method is studied. It was shown that AL25 chemical composition heterogeneity causes the consumption of a part of the anode current to homogenize the treated surface, which is reflected in minimizing the content of doping components at the initial processing stage. It was established that the growth of mixed oxides Al2O3·CoxOy relative mass is a function of time with a maximum at 55 minutes. The chemical, phase composition and surface morphology of the formed oxide layer depend on the oxidation time. The catalytic component content in the surface oxides varies from 0.2 to 23.3 at.% with an increase in processing time of 10 to 60 minutes. Maximum cobalt incorporation into the oxide layer occurs at PEO of 35–50 minutes, while the silicon content in the surface layers does not exceed 2 at.%, which is favorable for the catalytic properties. The cobalt oxide, preferably Co3O4, incorporation in the alumina α-Al2O3 matrix is visualized by the blue-violet color steroidal surface structures in the sites of micro-arc discharges. The alumina cobalt oxide mixture layers are characterized by a developed micro-globular surface which consists of spheroid conglomerate with an average size of 1–2 microns. There are some amorphous phases in the structure of mixed oxides due to non-equilibrium PEO conditions. The set of detected factors is a prerequisite for the high catalytic properties of oxide coatings. A promising field of Al2O3·CoxOy systems application is intra-cylinder catalysis in internal combustion engines.

The paper reports on an undulating topography initiating on the interface “coating/base material” under heterogeneous plasma flows to be generated by an explosion of yttrium powder on the aluminum-silicon base. We assumed that an undulating topography on the interface resulted from a combination of Rayleigh–Taylor and Kelvin–Helmholtz instabilities. A flow of an incompressible viscous two-dimensional fluid was considered in the field of bulk forces. The first layer made up of titanium or silumin is thought to be static, and the second one is accelerated perpendicular to the base material plane. A range of transversal velocities in the second layer was determined. Navier–Stocks equation and boundary conditions were stated for each layer. In a system Ti-Y Rayleigh–Taylor instability dominates at a transversal velocity of below 10 m/s, changing into Kelvin–Helmholtz instability at velocities above 10 m/s. In a system Al-Si-Y Kelvin–Helmholtz is dominant at velocities above 50 m/s due to lower density of the base material in comparison with titanium and a high acceleration of yttrium powder. The study highlights importance of the transversal velocity in yttrium layer for reasoning of undulating pattern formation on the interface “coating/base material” and distribution of yttrium particles in depth of the modified layer. Keywords: Heterogeneous plasma flows, Rayleigh–Taylor instability, Finite element method, Conservation laws