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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 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.

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.

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.

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.

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.

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.

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.

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 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.

The paper concerns the mechanical properties of hypoeutectic Al-Si alloy (silumin) with the addition of Cr, Mo, V and W. Changes in microstructure under the impact of these elements result in a change in the mechanical properties. Crystallization of Al-Si alloys determines grain size reduction, which causes a significant increase in their strength properties. Crystallization subjected to modifications through the influence of alloying additives can be described by the cooling curve run. Statistical relationships between the characteristic values of cooling curves and mechanical properties are investigated with data mining techniques of regression, especially regression trees. Such knowledge could provide an ability of a property prediction on the basis of cooling curves in terms of the benefits of a short time of the curve registration.

An Al–Si eutectic alloy was synthesized by the selective laser melting (SLM) method using a pilot wrought Al-Si powder (of Russian AKD-12 grade) as the starting material. On the basis of electron microscopy, the microstructure of the SLM alloy was certified with EDS mapping of elements (Al and Si). It has been established that the main structural component is an Al-based solid solution with a cellular-dendritic structure (with an average cell size of ~500 nm). The Si phase, which is a component of the eutectic, is located at the boundaries in the form of rounded crystals about ten nanometers in size. This paper presents the results of measuring the mechanical and nanomechanical properties, which show the competitiveness of the use of the pilot (experimental) powder.

The aim of this experiment was to investigate the influence of the Sr modifier in the Al-Si eutectic alloy on the structure change and its mechanical properties. For this reason, an Al-Si7Mg0.3 hypoeutectic silumin alloy was modified with the aim of improving the mechanical properties of the material, mainly by increasing the ductility and strength. The subject of investigation was analysis of morphology of excreted eutectic silicon. In order to investigate the surface, metallographic cross-sectional specimens were prepared using light and electron microscopy. A static tensile test was performed for detailed examination. It has been found that the addition of the AlSr10 modifier and, over the time of modification of 1 to 2 hours, has increased the mechanical properties, in particular the ductility.

The initial structure of AlSi9Mg alloy is com posed of granular and acicular β phase, with α phase as matrix. The hard, irregular, often pointed β phase is responsible for the poor mechanical properties of said alloy. This composition is responsible for the alloy's low strength parameters, and it limits the extent of practical applications. This study presents the results of modification of an AlSi9Mg alloy with strontium, boron and titanium in different ranges produced as a melted modifier added as powders and as rod. The influence of the analyzed additions on the microstructure and tensile strength of the silumin was presented in graphs. The used treatments 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.

The paper presents the results of tensile strength tests of AlSi21CuNiMg silumin made on a test stand. Silumin was under examination in an unmodified state and after modification with AlCu19P1.4 master alloy in quantity of 0.2% in relation to the mass of the alloy. Using a scanning microscope, the surface fractures obtained from tensile tests were tested. The structure and profiles of fractures were examined using an optical microscope. Modification of the tested silumin resulted in a favorable fragmentation and regular distribution of the crystals of the primary silicon in the alloy structure, which led to an almost twofold increase in the strength of the silumin samples at the final solidification stage from 3.5 to 6.6 MPa. As a result of these changes, the resistance of silumin to hot cracks should increase, which is of great importance when casting hypereutectic silumin in a metal mould that strongly inhibits the shrinkage of the castings.

The paper presents a review of existing methods to produce silumins. The possibility of obtaining foundry alloys using amorphous microsilica is shown. Different methods of adding SiO 2 particles into molten aluminum are studied: in the form of aluminum powder — SiO 2 master alloy tablets, particle mixing in the melt at the liquidus temperature and introducing SiO 2 together with a stream of argon. The paper provides calculations of Gibbs energy formation and change enthalpy for silicon reduction by aluminum from its oxide. Calculations demonstrated the thermodynamic possibility of silumin production using amorphous microsilica. The effect of alloying additives and impurities on the silicon reduction behavior is determined. It is found that magnesium can be used as a surface-active additive to remove oxygen from dispersed particle surfaces and reduce silicon from its oxide. It is determined that the method of aluminum-silicon alloy production by introducing amorphous microsilica preheated to 300 °С into the aluminum melt (t = = 900 °С) together with argon stream (with subsequent intensive mixing) features higher efficiency since it ensures producing aluminum-silicon alloys containing more than 6 wt.% of silicon and microstructure of pre-eutectic foundry silumins. Industrial application of the proposed method will improve the efficiency of the existing silumin production process due to savings on purchasing commercial crystalline silicon. Moreover, this technology will minimize the environmental impact by reducing the volume and subsequent eliminating sludge fields used as landfills for storing dust from silicon gas treatment systems containing up to 95 wt.% of amorphous microsilica.

The effect of the main impurities, added separately to an alloy, on aluminum-magnesium alloy corrosion resistance, and also in combination on the corrosion properties of secondary cast alloy AMg5K is studied. Comparative tests are conducted for corrosion resistance of industrial silumin and magnalium under different climatic conditions. Experimental results are provided for a study of the effect of alloy composition on corrosion properties under different climatic conditions.

To analyze the fatigue, researchers have tested commercial as-cast alloy of aluminum and silicon AK12 (eutectic silumin) and alloy VT1-0.

As mentioned in Chapter 2, commercial as-cast silicon-aluminum alloy (silumin) AK12 is used for the purpose of research. Its element composition according to GOST 1583—93 (Russian State Standard) is provided in Table 2.1.

На основі проведеного огляду функціональних покриттів на поршневих сплавах алюмінію зроблено висновок щодо доцільності застосування оксидних покриттів для підвищення показників міцності й зносостійкості деталей поршневої групи двигунів внутрішнього згоряння. Показано, що синтез оксидного шару на сплавах системи Al-Si (силумінах) можна здійснювати плазмо-електролітною обробкою у лужних електролітах з додаванням солей металів-допантів, зокрема кобальту. Це дозволить одержувати покриття, які володіють активністю у процесах каталітичного горіння палива. Запропоновано формування кобальтовмісних оксидних покриттів на поршневих сплавах здійснювати методом плазмо-електролітного оксидування в електроліті складу 0,4 моль/дм3 K4P2O7, 0,1 CoSO4 за густини струму 3–5 А/дм2 в режимі «спадаючої потужності». Встановлено, що в зазначених умовах протягом 15 хв оксидування на висококремністих сплавах АЛ30 и АК21 утворюється оксидний шар із вмістом до 4,7 ат.% кобальту. Наявність до 6,4 ат.% фосфору у складі синтезованого покриття сприятиме підвищенню теплостійкості оксидованої поверхні. При цьому вміст кремнію у поверхневих шарах зменшується у 4–5 разів порівняно із вихідним матеріалом. Показано, що морфологія та фазовий склад покриття змінюється з інкорпорацією допувального компоненту до його складу. Включення кобальту відбувається у вигляді термодіинамічно стійкого оксиду Co3O4 (CoO∙Co2O3), який кристалізується у гратці шпінелі, що поряд із високим ступенем розвинення поверхні є передумовою підвищення функціональних властивостей одержаних оксидних шарів. Розроблений спосіб було застосовано для нанесення кобальтовмісного покриття на поверхню поршня, що виготовлений зі сплаву АЛ30. Встановлено, що для одержання рівномірного оксидного шару слід додержуватись визначених технологічних параметрів. Прогнозовано використання поршня з нанесеним кобальтовмісним оксидним покриттям дозволить знизити кількість токсичних речовин з відпрацьованими газами та годинну витрату палива, що є перспективним для внутрішньоциліндрового каталізу., Based on the review of functional coatings on piston alloys of aluminum, a conclusion was made on the feasibility of using oxide coatings to increase the strength and durability of parts of the piston group of internal combustion engines. It is shown that the synthesis of the oxide layer on alloys of the Al-Si system (silumins) can be carried out by plasma electrolyte treatment in alkaline electrolytes with the addition of salts of dopant metals, in particular cobalt. This will allow to obtain coatings that have activity in the processes of catalytic combustion of fuel. It is proposed to form cobalt-containing oxide coatings on piston alloys by plasma-electrolytic oxidation in the electrolyte of 0.4 mol/dm3 K4P2O7, 0,1 mol/dm3 CoSO4 at current densities of 3–5 A/dm2 in the “decreasing power” mode. It is established that under these conditions during 15 min of oxidation on high-silicon alloys AL30 and AK21 an oxide layer with a content of up to 4.7 at.% Co is formed. The presence of up to 6.4 at.% of phosphorus in the synthesized coating will increase the heat resistance of the oxidized surface. At the same time, the silicon content in the surface layers decreases 4–5 times compared to the source material. It is shown that the morphology and phase composition of the coating changes with the incorporation of the additive component into its composition. The inclusion of cobalt occurs in the form of thermodynamically stable oxide Co3O4 (CoO·Co2O3), which crystallizes in the spinel crystal cell. This, along with a high degree of surface development is a prerequisite for improving the functional properties of the obtained oxide layers. The developed method was used for applying a cobalt-containing coating on the surface of a piston made of alloy AL30. It is established that in order to obtain a uniform oxide layer, certain technological parameters should be observed. The predicted use of a piston coated with cobalt-containing oxide coating will reduce the amount of toxic substances with exhaust gases and hourly fuel consumption, which is promising for intracylinder catalysis., На основе проведенного обзора функциональных покрытий на поршневых сплавах алюминия сделан вывод о целесообразности применения оксидных покрытий для повышения показателей прочности и износостойкости деталей поршневой группы двигателей внутреннего сгорания. Показано, что синтез оксидного слоя на сплавах системы Al-Si (силуминах) можно осуществлять плазменно-электролитной обработкой в щелочных электролитах с добавлением солей металлов-допантов, в частности кобальта. Это позволит получать покрытия, которые обладают активностью в процессах каталитического горения топлива. Предложено формирование кобальтосодержащих оксидных покрытий на поршневых сплавах осуществлять методом плазменно-электролитного оксидирования в электролите состава 0,4 моль/дм3 K4P2O7, 0,1 CoSO4 при плотности тока 3–5 А/дм2 в режиме «падающей мощности». Установлено, что в указанных условиях в течение 15 мин оксидирования на высококремнистых сплавах АЛ30 и АК21 образуется оксидный слой с содержанием до 4,7 ат.% кобальта. Наличие до 6,4 ат.% фосфора в составе синтезированного покрытия будет способствовать повышению теплостойкости оксидированной поверхности. При этом содержание кремния в поверхностных слоях уменьшается в 4–5 раз в сравнении с исходным материалом. Показано, что морфология и фазовый состав покрытия меняется с инкорпорацией допирующего компонента. Включение кобальта происходит в виде термодиинамично устойчивого оксида Co3O4 (CoO·Co2O3), который кристаллизуется в решетке шпинели, что наряду с высокой степенью развития поверхности является предпосылкой повышения функциональных свойств полученных оксидных слоев. Разработанный способ был применен для нанесения кобальтовмисного покрытия на поверхность поршня из сплава АЛ30. Установлено, что для получения равномерного оксидного слоя следует соблюдать указанные технологические параметры. Прогнозируемо использование поршня с нанесенным кобальтосодержащим оксидным покрытием позволит снизить выбросы токсичных веществ с отработавшими газами и часовой расход топлива, что является перспективным для внутрицилиндрового катализа.

The article presents studies specifying the friction coefficient $\mu$ and the amount of wear for cup 10-modified alloy A390.0 in combination with EN GJL-30 0.0. The tests were conducted using the T-01 tribological tester in the pin-disc system. The pin was from the tested material (A390.0) while the disc was made from cast iron EN GJL-300. In addition, the characteristics of the device and method of tribological studies were selected. An analysis of the surface decomposition of elements for the pin (silumin) and disc (cast iron) is also presented. The tests were carried out to determine whether the alloy under consideration meets the excessive requirements of materials intended for pistons for modern internal combustion engines used in automotive and aviation.

The research deals with the modification of AlSi5Cu2and AlSi10Cu2 alloy surfaces by the method of electron beam processing. It is established that the irradiation of the alloys by concentrated energy flow is accompanied by the increase in microhardness and covering the surface defects. Due to a great temperature difference between two media the surface melts at a superhigh rate and crystallizes again, because of it a grain size decreases resulting in the increase in microhardness. The arising tensile stresses contribute to the covering of the surface defects.

The aim of the research on the newly developed eutectic silumin type AlSi9NiCuMg0.5, developed and patented by a team of staff of the Faculty of Mechanical Engineering, was to determine the cause of the cracking of castings under operating conditions. When the technology was put into practice, the casting was cast and then used to break the entire casting section and create a crack that crosses the whole cross section. Castings were cast by low-pressure die casting technology, where the mold is fed into the mold cavity via a cast iron tube. The essence of the research was to perform a fractographic analysis of the fracture area, to identify the structure of the casting, to identify the structural components on the surface of the fracture surface by EDS analysis on an electron scanning microscope and to determine the chemical composition of the material in the area of refraction compared to the declared alloy. From these results we can clearly identify the cause of premature cracking of castings from the newly developed eutectic silumin. Additionally, material analyzes have been carried out to see if the material has been contaminated with iron, for example by dissolving a cast-iron filler tube or a batch material. From all the analyzes and fractographic investigations carried out, it can be stated that the initiator of crack insertion and the subsequent cracking of the casting under load is the high content of rough fragments of the fractured intermetallic phases of the Al5FeSi type on the fracture surface (over 20%), which are subject to fission. The high iron content was due to the dissolution of the cast iron ascension tube by low-pressure casting.

The effect of manganese and iron on the structure of AK12 silumin is studied by microscopic x-ray diffraction and spectrum analyses. Experimental alloys with Fe : Mn = 1 : 0, 1 : 0.5, 1 : 0.7 and 1 : 1 are investigated. Quantitative analysis of the microstructure is performed. The hub zone is studied for two models of car wheels. Recommendations for alloying AK12 silumin with manganese and iron for raising its mechanical characteristics are given.

Using up-to-date methods of material studies, it is revealed that the structure of as cast Al-Si alloy (silumin) is multi-phased and morphologically heterogeneous. It consists of solid solution grains and eutectic Al-Si with a diverse morphology. With the help of selective etching intermetallic compounds (AlNiCu and AlMg) are detected on the grain boundaries of α-solid solution. Treatment of silumin samples by the intense pulsed electron beam with the diverse density results in release of the second phase sub-micro and nano-dimensional particles. According to experiments optimal energy densities of the electron beam are 25, 30 and 35 J/sm2. Silumin irradiation results in a manyfold advance of mechanical and tribological properties of the surface layers. As found out, these characteristics of the surface layers change significantly due to the sub-micro and nano-dimensional structure of cellular crystallization formed by the electron beam, which is free of primary inclusions consisting of silicon and intermetallic compounds.

The effect of equal-channel angular pressing (ECAP) in an equal-channel stepped die on the microstructure and the mechanical properties of silumin AK9 (Al–Si–Mn–Mg) modified by a master alloy with nanostructured carbon in the form of fullerene black and synthesized glassy carbon particles formed during manufacturing the master alloy is studied. Silumins belong to nondeformable cast alloys; however, ECAP at 500°C makes its plastic deformation up to three passes possible. Three passes of deformation significantly refine the structure of the AK9 modified silumin. ECAP results in the refinement of silicon inclusions, which are of the fabrication origin and do not undergo plastic deformation.

One of the most common castings applied in industrial production is aluminium-silicon alloy (ca. 9% Si with Mg). The Al-SiMg alloys have high corrosion resistance, high strength to weight ratio with modifications, very good castability, a low thermal-expansion coefficient, and relatively good wear resistance. These properties make it possible to widely apply the foundry Al-9% SiMg alloy to number of aviation, automotive, and others materials working on tribological applications. Similar to silumins, the aluminium bronze CuAl10Fe3Mn2 is characterized by good mechanical properties and wear and corrosion resistance. This paper presents the research on the treatment of Al-9%SiMg alloy with a composition of CuAl10Fe3Mn2 in different mass ranges. The experiments were conducted by a factor plan 23 for three independent variables. The main additions were strontium, Al-9%SiMg, aluminium bronze, as well as pure or melted with raw silumin. The effect of the tested additions on the microstructure and tensile strength of the Al-9%SiMg alloy was presented in figures. All analysed parameters (mechanical and tribological) of the hypo-eutectic Al-9%SiMg alloy with tested bronze additions are improved. Based on the analysis of the study results, it was found that the microstructure and tensile strength of the tested alloy are determined through the contents introduced of CuAl10Fe3Mn2 to the alloy.

We studied the process of formation of cobalt-containing oxide coatings using plasma-electrolytic oxidizing of the aluminum alloy AK12M2MgN in pyrophosphate electrolytes. It was established that the use of given type solutions contributes the homogenization of silumin surface and creates preconditions for the dopants incorporation to the growing oxide coating. It is shown that PEO parameters depend on the concentration ratio of cobalt sulfate and potassium pyrophosphate in a working solution. Based on the results of experimental study, we demonstrated the ways to control the structure and surface morphology of cobalt-containing PEO-coatings through the variation in the concentrations of electrolyte components. The composition of a pyrophosphate electrolyte for the formation of oxide PEO-coatings with a high cobalt content and developed surface morphology is substantiated. It is noted that the obtained oxide coatings could be used in catalytic reactions in order to decompose natural and technogenic toxicants.

The object of research is the processes of the piston alloy AK12M2MgH treatment by the method of plasma electrolytic oxidation (PEO) with the formation of ceramic underlying coatings. One of the most problematic places is the influence of the chemical composition of the Al-Si alloy on the process of treatment and formation of ceramic coatings. It is established that electrochemical technologies are widely used to modify the surface of silumins by forming coating of various composition and purpose. In the course of the study it was shown that PEO of piston silumin should be carried out in alkaline complex electrolytes with the addition of manganese and/or cobalt salts. This makes it possible to homogenize the surface layer of the alloy by composition, to reduce the content of its alloying components and to create conditions for the formation of a uniform oxide coating with incorporation of the admissible components. It has been established that oxidation in pyrophosphate cobaltous solution allows obtaining mosaic structures of blue-violet color with cobalt content up to 24 at %. PEO silumin in the manganous alkaline electrolyte provides the formation of a brown-black ceramic-like layer with manganese content up to 35 at %. Consecutive PEO treatment in these solutions leads to the formation of a mixed fine-dispersed porous oxide coating with a total content of dopant 25–30 at %. Based on the research results, it has been proposed to oxidize the piston silumin in a regime of incident power to form uniform coatings with a high content of dopant. Obtained oxide systems have a developed surface and a significant content of catalytically active components. In comparison with the known methods of PEO treatment of piston silumin, the silicon content in the surface oxide layers does not exceed 3 at %, which is one of the requirements for catalytically active materials. The ceramics-like coatings show high catalytic activity in model oxidation reactions of CO and benzene and reduce the emission of toxic gas emissions from internal combustion engines. The proposed systems are promising for use in intracylindrical catalysis technologies and improving the fuel economy of engines.

The study covers the electrochemical and corrosion behavior of 4 alloys (wt.%): Al–6Ca (Al6Ca), Al–6Ca–1Fe (Al6Ca1Fe), Al–1Fe (Al1Fe), AK12M2. High Fe content (up to 1 %) in the alloys is required for high productivity of die-casting processes. Electrochemical tests were conducted in the 3 % NaCl aqueous solution at 26±0,5 °С using the IPC-Pro 3A (IPC-2000) digital potensiostat. Potentiodynamic anodic polarization was performed at a scan rate of 1 mV/s. The initial polarization potential was –800 mV (SHE). The potential scanning direction was reversed at a «critical» current density icr = 10 mA/cm2 with the same scan rate of polarization. The tendency of the alloy for pitting formation was determined by the Qdir/Qrev ratio (the amounts of electricity passed through the electrode before pits occur and before repassivation) and the bases of pitting resistance: difference between the pitting potential (Epit) and the equilibrium potential (Eeq); difference between the repassivation potential (Erep) and the equilibrium potential (Eeq). Corrosion tests of cast aluminum alloys were carried out by holding the samples in a salt spray chamber and in the 3 % NaCl aqueous solution for 700 h. The Olympus GX51 optical microscope was used to assess the morphology of sample surfaces after their holding. It is found that the Al6Ca1Fe and Al6Ca experimental alloys placed in the 3 % NaCl aqueous solution are not susceptible to pitting corrosion as opposed to the AK12M2 industrial alloy and Al1Fe. It is assumed that the higher corrosion resistance of Al6Ca1Fe is due to the entry of Fe into the Al10CaFe2 intermetallide. The intermetallide is not an effective cathode with respect to Fe due to significant negative potentials of Al and Ca. Al6Ca1Fe is a promising alloy for industrial use due to its high casting and mechanical properties that are not inferior to the eutectic silumin alloy and even surpass it in terms of corrosion resistance.

The electrochemical and corrosion behavior of four alloys (wt %) is investigated: Al–6Ca (further Al6Ca), Al–6Ca–1Fe (further Al6Ca1Fe), Al–1Fe (further Al1Fe), and Ak12M2. An increased iron content (up to 1%) in alloys is necessary for the high productivity of casting under pressure. Electrochemical studies are performed in a 3% aqueous NaCl solution at 26 ± 0.5°C using an IPC-Pro 3A digital potentiostat (IPC-2000). Anodic polarization is performed in a potentiodynamic mode with a potential scan rate of 1 mV/s. The initial polarization potential is–800 mV with respect to the standard hydrogen electrode. The direction of the potential scan was changed to inverse upon the “critical” current density icr = 10 mA/cm2 performing polarization with the same rate. The tendency of the alloy to form pits was judged by the ratio of amounts of electricity that passed through the electrode before pitting formation and their repassivation (Qfor/Qinv) and values of pitting resistance bases: the difference in the pitting formation potential and stationary potential and the difference in the repassivation potential and stationary potential. Corrosion tests of casting aluminum alloys were performed holding the samples in a salt fog chamber and in a 3% aqueous NaCl solution for 700 h. After these holdings, the surface morphology of the samples was investigated using an Olympus GX51 optical microscope. It is established that Al6Ca1Fe and Al6Ca experimental alloys, in contrast to the AK12M2 industrial alloy and Al1Fe alloy, are not subjected to pitting corrosion in a 3% aqueous NaCl solution. It is assumed that the increased corrosion resistance of Al6Ca1Fe alloy is caused by the fact that iron enters the Al10CaFe2 intermetallic compound, which is not an efficient cathode because of the considerable negative potentials of Al and Ca. Due to the high casting and mechanical properties of the Al6Ca1Fe alloy, which are no worse than the properties of eutectic silumin and surpass them by the corrosion resistance, the Al6Ca1Fe alloy is promising for use in an industrial scale.

Metallography, electron microscopy, and X-ray diffraction have been used to investigate structural transformations that take place in a 10-μm-thick surface layer in aluminum and Al–17% Si alloy under conditions of sliding friction and subsequent oxidation at 100 and 200°C for 1 h. Friction-induced deformation has been carried out at room temperature in air and at–196°C in liquid nitrogen by reciprocating sliding of a cylindrical indenter made of cubic boron nitride at a rate of 0.014 m/s and a load of 98 N. It is shown that deformation under these conditions forms nanocrystalline structures in the surface layer in aluminum and Al–17% Si alloy and increases their microhardness by a factor of 1.8–3.5. A high contact deformation and a high affinity of oxygen to aluminum and silicon cause the formation of anomalously supersaturated solid solutions of oxygen in aluminum and silicon in the surface layer of the alloy during friction. Oxidation at 100°C (1 h) of the deformed Al–17% Si alloy increases its microhardness due to the decomposition of anomalously supersaturated solid solutions of oxygen in aluminum and silicon and the formation of their oxides.

An increase in the sum of alloying elements in industrial silumins causes the formation of excess intermetallic phases in their structure. When introducing modifiers in such alloys above a certain amount, structural components are coarsened because of overmodification, which can cause a decrease in the mechanical properties of cast alloys. The optimal consumption of the modifying microcrystalline remelt decreases from 0.6 to 0.3 wt % with an increase in the sum of alloying elements in alloys from 7.35% (AK7ch) to 14.3% (AK10M2N). When using the AlTi5 master alloy, the optimal amount of introduced titanium decreases from 0.05 to 0.01% and, in the case of the AlTi5B1 master alloy, from 0.02 to 0.01%. The modifying effect of the AlSr10 master alloy enhances with an increase in the silicon content with smaller amounts of strontium introduced into alloys. It is shown that the consumption of the metallic modifier depends on its modifying ability, as well as the sum of alloying elements in the modified silumin.

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 solidification of the AK12 alloy processed by a standard flux and a combined modifying flux, which significantly increases the mechanical properties of the alloy at a significant increase in the modifying effect time, is studied. The experimental results are simulated using the ProCAST software package.

The phase composition of the surface layer of AlSi10Cu2Ni and AlSi5Cu2 silumins after electron beam processing has been studied by the methods of X-ray phase analysis in the research. It has been detected that in the initial state the main phases of AlSi10Cu2Ni silumin under study is a solid solution based on aluminium, silicon and intermetallides, ones of which are Fe2Al9Si2 and Cu9Al4 phases. The X-ray phase analysis of AlSi5Cu2 silumin samples irradiated by the pulsed electron beam has shown that the main phases of the alloy are also a solid solution based on aluminium, silicon and intermetallides, and Fe2Al9Si2 phase is present. The analysis of aluminium diffraction maximums has shown that they are splitted. This permits one to speak about the existence of two solid solutions based on aluminium being different in crystal lattice parameters and, consequently, the concentration of alloying elements. The first type— solid solution based on aluminium with a larger parameter of crystal lattice Al1; the second type—with a smaller parameter of crystal lattice Al2. The alloys’ irradiation by pulsed electron beam is accompanied by the change in crystal lattice parameter of AlSi10Cu2Ni (solid solution based on aluminium) and AlSi5Cu2 (phases Al1 and Al2). Probably, the reason of the change in crystal lattice parameter in AlSi10Cu2Ni and AlSi5Cu2 alloys is the variation in alloying elements concentration in solid solution of the phases.

The paper analyzes the effectiveness of modifying aluminum alloys with active additives of microcrystalline alloys of different types. Production technologies have been developed, and the optimum amount of the most effective modifiers and active reinforcing additives for silumin made from recyclable materials has been determined; the connection of changes of structure with the parameters of mechanical properties of secondary silumin was established. It was found that the optimum amount of modifier-ligature Al-Ti5 was 0,1% by weight of liquid metal. Using more modifiers is not rational from the standpoint of materials science, economics, and ecology. The addition of such additive provided in the cast and heat-treated material an increase in the hardness by (20–30)% and tensile strength by (15–25)% due to the change in shape and dispersion of the formed intermetallic phases, reduction of porosity and increase in density. The use of non-deficient, cheap and environmentally friendly active additives in combination with traditional refining-modifying treatment can provide a significant increase in the properties of cast aluminum alloy products and are recommended for use in industry.

n 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. Keywords: silumin, shavings, extrusion, plastic deformation, heat treatment

The paper presents the analysis of possible combinations of raw materials during manufacturing bimetallic compositions. A variety of materials makes it necessary to apply new combinations of familiar processes of materials processing and search for new ways of bimetals production meeting the needs of different branches of industry. The possibilities of obtaining bimetallic compounds on the basis of casting alloys and powder sintered materials are not sufficiently studied. By means of the analysis, carried out using a morphological matrix, a new method of manufacturing bimetallic products based on the technology of casting with crystallization under pressure was developed. An experimental press mold and an experimental stand were developed to study the main parameters of the proposed process on the samples in the form of bimetallic bushings—models of bimetallic bearings. Casting aluminum alloy AK9ch was used for the base material. The working layers were sintered powder materials made of graphite bronze and iron. The main methods of studying the obtained bimetallic samples were mechanical tests of strength of the layers interconnection and metallographic studies of their interconnection zone. The paper discusses the issues of searching for rational modes of casting with crystallization under the pressure of aluminum alloys together with the working elements made of sintered materials with special properties. The possibility of application of the obtained bimetallic products in sliding friction joints used in general mechanical engineering products is considered. Acoustic emission, radiographic testing, pressure vessels, stainless steel, cracks in the welds, sequence of application of testing methods

Aluminum alloys are widely used to produce automotive components, thanks to their great mechanical properties&ndash, to&ndash, density ratio. Engine components such as pistons are conventionally produced by casting of Al&ndash, Si eutectic alloys (Silumin alloys) such as EN AC 48000. Due to the harsh working conditions and the lower ductility if compared to aluminum&ndash, silicon alloys with lower silicon content, pistons made of this alloy are prone to fatigue failures in the skirt region. In order to overcome such limits, the use of a Functionally Graded Material (FGM) in the production of a piston is proposed. The adoption of a functionally graded architecture can maximize the properties of the component in specific areas. A higher level of thermal resistance in the crown of the piston can be achieved with EN AC 48000 (AlSi12CuNiMg), while higher elongation at rupture in the skirt region would be conferred by an EN AC 42100 (AlSi9Mg0.3). The FGM properties are strictly related to the metallurgical bonding between the alloys as well as to the presence of intermetallic phases in the alloys junction. In the present article, the characterization of gravity casted FGM samples based on Al&ndash, Si alloys with respect to microstructure and mechanical testing is presented, with a specific focus on the characterization by impact testing of the joint between the two alloys.

The paper characterizes a composite with dispersion phases cast via the use of stir casting method on an aluminum matrix. A mixture of aluminum with FexAly and SiC powders was achieved in the process of mechanical alloying and self-propagating high temperature synthesis (ASHS). Chemical composition of agglomerates was chosen in such a way that the strengthening components made up 25% of the mass of the AlSi10Mg0.5Mn0.6 (EN AC-43400) alloy matrix. The characteristic temperatures of crystallization of the tested alloy were measured by thermal analysis ATD (analysis thermal derivative). A change of chemical and phase composition was confirmed in the elements of the intermetallic phase FeAl in the aluminum matrix. A silumin casting structure was achieved, with the matrix including micro-areas of ceramic phases and intermetallic phases, which are characteristic for hybrid strengthening. A refinement of dendrites in solid solution &alpha, was found, together with a transition from a binary plate eutectic composition &alpha, (Al) + &beta, (Si) into modified eutectic composition.

An increase in the sum of alloying elements in industrial silumins causes excess intermetallic phases to form in their structure. When the amount of modifiers introduced into such alloys exceeds a certain amount, structural components coarsen due to overmodification, which may cause deterioration of mechanical properties of cast alloys. As the amount of alloying elements in alloys increases from 7,35 % (АК7ch) to 14,3 % (АК10М2N), the optimum consumption of the modifying microcrystalline remelt decreases from 0,6 to 0,3 wt.%. The optimum amount of introduced titanium is reduced from 0,05 to 0,01 % when using the AlTi5 master alloy and from 0,02 to 0,01 % when using the AlTi5B1 master alloy. With an increase in the silicon content, the modifying effect of the AlSr10 master alloy is enhanced, while the amounts of strontium introduced into alloys are smaller. The paper demonstrates that metallic modifier consumption depends on its modifying property, as well as on the sum of alloying elements in the modified silumin.

The research and development status of casting magnesium alloys including the commercial casting alloys and the new types casting alloys are reviewed, with more attention to microstructure and mechanical properties of modified-AZ91, AM60 and WE43 alloys with various additions, and new types of low cost casting alloys and high strength casting alloys. The modification and/or refinement of Mg 2 Si phase in Mg–Al–Si based casting alloys by various additions are discussed and new purifying technologies for casting magnesium alloys are introduced to improve the performance. The modified AZ81 alloy with reduced impurities is found to have the tensile strength of 280 ± 6 MPa and elongation of 16% ± 0.7%. The fatigue strength of AZ91D alloy could be obviously improved by addition of Ce and Nd. The Mg–16Gd–2Ag–0.3Zr alloy exhibits very high tensile and yield strengths (UTS: 423 MPa and YS: 328 MPa); however, its elongation still needs to be improved.

Phase transformations of an Al–20 at % Si high-silicon hypereutectic alloy have been studied by differential barothermal analysis at temperatures of up to 800°C in argon compressed to 100 MPa. High pressure has been shown to raise the melting point of the alloy by 5°C during heating and to lower the eutectic solidification temperature by 5°C during cooling in comparison with the canonical phase diagram of the Al–Si system. At a temperature of 553°C, heating and cooling lead to silicon dissolution and decomposition of the aluminum-based solid solution, respectively. After high-pressure solidification, the silicon particles in the alloy have a bimodal size distribution. Quantitative porosity characteristics in the alloy after a barothermal scanning cycle are similar to those in the as-prepared alloy. The lattice parameters of the silicon and aluminum remain unchanged. The microhardness of the aluminum matrix of the alloy corresponds to that of pure aluminum.

Automation of machining operations, being result of mass volume production of components, imposes more restrictive requirements concerning mechanical properties of starting materials, inclusive of machinability mainly. In stage of preparation of material, the machinability is influenced by such factors as chemical composition, structure, mechanical properties, plastic working and heat treatment, as well as a factors present during machining operations, as machining type, cutting parameters, material and geometry of cutting tools, stiffness of the system: workpiece – machine tool – fixture and cutting tool. In the paper are presented investigations concerning machinability of the EN AC-AlSi9Cu3(Fe) silumin put to refining, modification and heat treatment. As the parameter to describe starting condition of the alloy was used its tensile strength Rm. Measurement of the machining properties of the investigated alloy was performed using a reboring method with measurement of cutting force, cutting torque and cutting power. It has been determined an effect of the starting condition of the alloy on its machining properties in terms of the cutting power, being indication of machinability of the investigated alloy. The best machining properties (minimal cutting power - Pc=48,3W) were obtained for the refined alloy, without heat treatment, for which the tensile strength Rm=250 MPa. The worst machinability (maximal cutting power Pc=89,0W) was obtained for the alloy after refining, solutioning at temperature 510 °C for 1,5 hour and aged for 5 hours at temperature 175 °C. A further investigations should be connected with selection of optimal parameters of solutioning and ageing treatments, and with their effect on the starting condition of the alloy in terms of improvement of both mechanical properties of the alloy and its machining properties, taking into consideration obtained surface roughness.

The paper presents tribological properties of A390.0 (AlSi17Cu5Mg) alloy coupled in abrasive action with EN-GJL-350 grey cast-iron. The silumin was prepared with the use of two different technologies which differed in terms of cooling speed. In the first case the alloy was modified with foundry alloy CuP10 and cast to a standard tester ATD and in case of second option the modified alloy was cast into steel casting die. Due to different speed of heat removal the silumins varied in structure, particularly with size of primary crystals of silicon and their distribution in matrix which had a significant influence of friction coefficient in conditions of dry friction.

Possibility of using of aluminum A7 instead of A8 to reduce the cost automobile wheel discs, made from alloy AK12 by casting under low pressure is studied. The microstructure and properties of six experimental alloys are investigated. It is found that use of primary aluminum A7 instead of A8 is possible at insertion of a compensator element-manganese in an amount of not more than 0.20–0.25 wt %. at the content of iron is not more than 0.20-0.25 wt. %, that is ratio Fe: Mn has to be equal 1: 1. The mechanical properties demanded GOST 50511-93 are received.

The surface layer under analysis was formed as a result of diffusion bonding of a thin AlSi20 plate to a magnesium substrate followed by laser melting. Depending on the process parameters, the laser beam melted the AlSi20 plate only or the AlSi20 plate and a layer of the magnesium surface adjacent to it. Two types of microstructure of the remelted layer were thus analyzed. If the melting zone was limited to the AlSi20 plate, the microstructure of the surface layer was typical of a rapidly solidified hypereutectic Al–Si alloy. Since, however, the liquid AlSi20 reacted with the magnesium substrate, the following intermetallic phases formed: Al 3 Mg 2 , Mg 17 Al 12 and Mg 2 Si. The microstructure of the modified surface layer of magnesium was examined using optical, scanning electron and transmission electron microscopy. The analysis of the surface properties of the laser modified magnesium revealed that the thin layer has a microstructure of a rapidly solidified Al–Si alloy offering good protection against corrosion. By contrast, the surface layer containing particles of intermetallic phases was more resistant to abrasion but had lower corrosion resistance than the silumin type layer.

We describe barothermal processing (hot isostatic pressing) of an Al–10 at % Si binary alloy for 3 h at a temperature of 560°C and pressure of 100 MPa. The results demonstrate that this processing ensures a high degree of homogenization of the as-prepared alloy, which is chemically and structurally inhomogeneous. The morphology of the silicon microparticles in the material suggests that heat treatment of the Al–10 at % Si alloy at 560°C and a pressure of 100 MPa leads to a thermodynamically driven, essentially complete silicon dissolution in the aluminum matrix and the formation of a metastable, supersaturated solid solution, which subsequently decomposes during cooling. We analyze the associated porosity elimination process, which makes it possible to obtain a material with 100% relative density. Barothermal processing of the Al–10 at % Si alloy is shown to produce a bimodal size distribution of the silicon phase constituent: microparticles 1.6 µm in average size and nanoparticles 43 nm in average size. Barothermal processing is shown to reduce the thermal expansion coefficient of the alloy, and the microhardness of the two-phase alloy is determined. Based on the present results, we conclude that barothermal processing is an effective tool for eliminating microporosity from the Al–10 at % Si alloy, reaching a high degree of homogenization, and producing a near-optimal microstructure, which surpasses results of conventional heat treatment of the material at atmospheric and reduced pressures.