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Evaluating casting’s mechanical stress is of significant interest from a safety inspection’s point of view. Residual stress, in particular, leads to an early or even immediate failure of some parts. Therefore, several methods exist to determine casting’s external and internal strain leading to stress. By determining the state of stress and residual stress, it is possible to design casting parts that are much safer. The present concept of a test bench shows a new way of inspecting parts for safety reasons using an optical fiber confocal chromatic sensor to measure strain. The method is based on the deep-drilling method, where a minimal invasive hole is placed at an area of interest in the first step. In a second step, this hole is then precisely measured to be able to map the borehole. From this information, conclusions can be drawn of any forces acting on the inspected part. In this case, the concept of the test bench uses gun drills to place boreholes measuring 6.0 mm in diameter with up to 500.0 mm in depth, and for the inspection, a confocal sensor with a precision of ± 100.0 nm in dissolving distances is used. This work focuses on evaluating the test bench’s precision in conducting such measurements and on how an external thermal load and mechanical load influence the results when conducting differential measurements. The experiments are performed on typical cast alloys such as iron cast and Zamac.Article Highlights: Test bench prototype using confocal chromatic spectroscopy. Hybrid system combining different technologies for placing and mapping boreholes in cast parts. Method for mobile inspection of defects in metal parts with non-contact measurement technologies. [ABSTRACT FROM AUTHOR]

This study investigates the effect of hot isostatic pressing (HIPping) on the static and fatigue properties of sand-casting A356 aluminium alloys. HIPping is a method to improve the fatigue properties in aluminium cast material by reducing or eliminating the inner porosities. Investigation of the complex interaction between the microstructural features on mechanical properties before and after the HIPping process was examined using computed tomography and scanning electron microscopy (SEM). Castings generally contain pores and defects that have a detrimental impact on the fatigue properties. The HIPping process closes the porosities in all investigated samples with an increase in density. Without significant defects, the mechanical performance improved in the finer microstructure. However, a considerable variation in the results was found between the different conditions, whereas the coarser microstructure with larger porosities before HIPping showed remarkably reduced results. The high-cycle fatigue-tested samples showed reduced fatigue propagation zone in the coarser microstructure. Moreover, large cleavage areas containing bifilms in the fracture surfaces indicate that the healing process of porosities is inefficient. These porosities are closed but not healed, resulting in a detrimental effect on the static and dynamic properties. [ABSTRACT FROM AUTHOR]

Abstract Evaluating casting’s mechanical stress is of significant interest from a safety inspection’s point of view. Residual stress, in particular, leads to an early or even immediate failure of some parts. Therefore, several methods exist to determine casting’s external and internal strain leading to stress. By determining the state of stress and residual stress, it is possible to design casting parts that are much safer. The present concept of a test bench shows a new way of inspecting parts for safety reasons using an optical fiber confocal chromatic sensor to measure strain. The method is based on the deep-drilling method, where a minimal invasive hole is placed at an area of interest in the first step. In a second step, this hole is then precisely measured to be able to map the borehole. From this information, conclusions can be drawn of any forces acting on the inspected part. In this case, the concept of the test bench uses gun drills to place boreholes measuring 6.0 mm in diameter with up to 500.0 mm in depth, and for the inspection, a confocal sensor with a precision of ± 100.0 nm in dissolving distances is used. This work focuses on evaluating the test bench’s precision in conducting such measurements and on how an external thermal load and mechanical load influence the results when conducting differential measurements. The experiments are performed on typical cast alloys such as iron cast and Zamac.

The influences of temperature-kinetic parameters on the morphology, dispersion, and gradient of their cast structure are studied using the example of castings of 30ХГС and У7Л steels obtained under the condition of directional cooling of their end surfaces during crystallization with different intensity of heat removal (5°C/s and 300°C/s), as well as on the length of the transcrystallization zone and its influence on the wear resistance in various sections of castings during abrasive wear. A regular increase in the length of the transcrystallization zone (zone of columnar crystals) is established, corresponding to an increase in the superheat temperature of the steel melt in the range of 50°C-150°C above the liquidus temperature and the cooling rate during the crystallization of castings. As shown, the maximum resistance to abrasive wear is observed during high-rate crystallization of castings and corresponds to an increase in the length of the transcrystallization zone in the cross-sections of samples oriented across the direction of heat removal and advancement of the crystallization front. Such anisotropy of the structure of the transcrystallization zone makes it possible to increase additionally the wear resistance by 13-18% and opens up new prospects for the engineering of cast products to improve their operational properties. [ABSTRACT FROM AUTHOR]

It has been a challenging mission to assure that ductile iron castings meet customer internal soundness specifications with acceptable process capabilities to get approval in new automotive model launch processes. Shrinkage conditions were investigated in the new program launch stage. Several factors were investigated including carbon equivalent, carbon levels, silicon levels, molten iron preconditioners and other additives. This study investigated shrinkage size by taking digital photos and measuring each shrinkage indication size using software comparing to the size limits from the customer Internal Soundness Specification. Thermal analysis was utilized to evaluate iron conditions to correlate shrinkage tendency. Statistical tools were applied to determine whether the factors in this investigation truly affected casting shrinkage characteristics. High process capability (Ppk) values were achieved by adopting optimal process parameters and using proper additives, and the program was launched successfully. Additional studies were conducted to confirm that the ductile iron meets customer specification including mechanical properties, microstructure, impact property, and casting hardnessunder all conditions. [ABSTRACT FROM AUTHOR]

Foundry production is a versatile industry that allows the production of products of almost any configuration and geometric dimensions. These products can be made from materials based on various metals and alloys, bimetallics, and composite materials. The obtained products can have uniform or gradient properties. However, to obtain a product with significantly different properties on the surface and in the volume from the casting, it is expedient to apply coatings with desired properties on the castings that complement the properties, allowing the improvement of coating performance. The paper focuses on the production of cast composite materials with improved surface properties. Various types of coatings based on high‑entropy alloys, cermets, polymers, carbon nanotubes, capable of enhancing the properties of cast composite materials, are considered. The classification and peculiarities of applying these coatings on the surface of composite materials are presented. The prospects of using these coatings to improve the properties of cast composite materials are shown.

The foundry industry is an important component of the economy on which other progressive industries depend. The reliability of the products it manufactures is determined by the technologies used, but, most importantly, it ensures the expected level of quality. The purpose of the article is to develop a synergistic quality-cost model for the improvement of casting products. The model is based on an integral methodological configuration that makes it possible to determine the level of relevance of the causes of casting nonconformity in the quality-cost context. The model integrates techniques such as the Pareto-Lorenz diagram, ranking, brainwriting, Ishikawa diagram, Likert rating scale, and matrix diagram. Verification of the method by its implication in the manufacturing process of a gearbox casting is performed. The model makes it possible to identify quality-cost relationships between key categories of problem causes and major product nonconformities. The main causes of the loss of quality stability of the analyzed product are found to be low quality of molding sand, poor technical condition of foundry equipment (too infrequent repairs and overhauls), and ineffective quality control. Carrying out the analysis made it possible to develop appropriate improvement measures. It is proposed to implement changes in the casting process, implement the TPM method, conduct periodic training, develop job instructions, implement a control system, and provide supervision of employees. Further research directions will concern the implications of the method within the other positions in the casting company and its development towards automation of analysis. [ABSTRACT FROM AUTHOR]

Research shows the possibility of replacing forged 12X18H10T steel billet with castings obtained in thin-walled metal-shell molds with forced cooling. In tests, the strength, plasticity, and impact strength of the forged and cast components are compared. The macrostructure of the steel samples is studied, as well as their sulfur impressions and the distribution of nonmetallic inclusions. The mechanical properties of the castings match those of the forged billet. The castings are characterized by somewhat lower strength but greater plasticity and impact strength. [ABSTRACT FROM AUTHOR]

It is shown that the main modifying phases cannot serve as centers of crystallization of α‑phase microcrystals during solidification of magnesium‑manganese alloys.The superheating modification of these alloys is an adsorption‑nanostructural process. It is shown that adsorbed hydrogen acts as a modifying element of the structure of castings of magnesium‑manganese alloys. The mechanism of their modification by overheating consists of a significant decrease in the concentration of adsorbed hydrogen due to the predominance of its desorption processes from elementary magnesium and manganese nanocrystals in liquid magnesiummanganese alloys. The mechanism of modification of the main modifying phases of these alloys consists of a significant decrease in the concentration of adsorbed hydrogen in the melts through a significant decrease in the concentration of dissolved hydrogen.

The paper presents an attempt to produce aluminum matrix composites reinforced with short carbon fibers by precision casting in a chamber with a pressure lower than atmospheric pressure. The composite casting process was preceded by tests related to the preparation of the reinforcement. This is related to the specificity of the precision casting process, in which the mold for shaping the castings is fired at a temperature of 720°C before pouring. Before the mold burns, the reinforcement must be inside, while the carbon fiber decomposes in the atmosphere at 396°C. In the experiment, the reinforcement in the form was secured with flake graphite and quartz sand. The performed firing procedure turned out to be effective. The obtained composite castings were evaluated in terms of the degree of alloy saturation and the displacement of carbon fibers. As a result of the conducted tests, it was found that as a result of unfavorable arrangement of fibers in the CF preform, the flow of metal may be blocked and porosity may appear in the casting.

It has been shown that elementary crystalline cells of α‑phases of tin, aluminum bronzes and main modifying phases do not correspond to the principle of structural and dimensional correspondence of Dankov‑Konobeevsky. Modifying structures in tin and aluminum bronze castings is a nanostructured process. The main role of tin and aluminum bronze modifiers is to significantly reduce the concentration of adsorbed hydrogen, which prevents the formation of crystallization centers of α‑phase microcrystals in castings when they solidify.

It has been shown that the main influence on the crystallization of heat‑resistant chromium steels is hydrogen. It is a demodifying element of the casting structure. The mechanism of the influence of hydrogen on the crystallization of heat‑resistant chromium steels can be explained from the position of nanostructured crystallization of casting alloys. Dissolved hydrogen atoms, adsorbing on elementary nanocrystals of iron and chromium in melts of heat‑resistant chromium steels, prevent the combination of nanocrystals into nuclei of crystallization of α‑phase microcrystals. As a result, castings with an unmodified structure are obtained. Reduction of hydrogen concentration in melts of heat‑resistant chromium steels contributes to formation of modified structure in castings at their hardening.

Polishing operations are mandatory in the manufacturing of floors and terrazzo, which are performed with grinding wheels. This study is carried out in two main stages, a laboratory study and later a study in the experimental pilot plant where the obtaining of abrasive materials from the aluminothermic processing of solid industrial wastes and Cuban minerals is approached. Different mixtures composed of mill scale and aluminum chips to which different proportions of limestone are added are studied. As a result of the process, a high hardness ceramic is obtained as the main product and a metal as a byproduct. The results of the process are evaluated on the basis of the metal and slag yields. The behavior of the ceramic as an abrasive material is evaluated by means of scratch tests on glass, as well as the behavior of the powders during setting with p-350 cement. Finally, a real working test of the abrasive obtained is carried out, achieving good results, which justifies the production on a larger scale of the abrasive materials with the objective of substituting the imported abrasive. The proposed technology constitutes a great step towards sustainability, since it would allow to substitute the importation of this product, minimizing its price and using Cuban industrial waste and minerals as raw materials. [ABSTRACT FROM AUTHOR]

Dissolved hydrogen acts as a demodifying element in the formation of aluminum oxide microcrystals in liquid steels. Hydrogen atoms in liquid steels serve as surface-active elements for aluminum oxide microcrystals. Modifiers significantly reduce the hydrogen concentration in steel melts. This enhances the process of coagulation of aluminum oxide microcrystals into large particles that quickly float in liquid steels. To more effectively remove aluminum oxide particles from them, the casting process should not begin immediately after treating steel melts with modifiers. [ABSTRACT FROM AUTHOR]

Expert analysis of the quality of reclaimed castings permits estimation of their structural reliability. Monitoring by visual, instrumental, and capillary methods permits identification of the technological deficiencies responsible for rejection and discarding of the workpiece. The introduction of electronic information systems with intermediate digital monitoring of casting production is prompted by the inconsistent appearance of casting defects. Product life cycle management (PLM) provides the basis for ensuring the quality of machine components in an import substitution strategy. [ABSTRACT FROM AUTHOR]

The paper presents an attempt to produce aluminum matrix composites reinforced with short carbon fibers by precision casting in a chamber with a pressure lower than atmospheric pressure. The composite casting process was preceded by tests related to the preparation of the reinforcement. This is related to the specificity of the precision casting process, in which the mold for shaping the castings is fired at a temperature of 720°C before pouring. Before the mold burns, the reinforcement must be inside, while the carbon fiber decomposes in the atmosphere at 396°C. In the experiment, the reinforcement in the form was secured with flake graphite and quartz sand. The performed firing procedure turned out to be effective. The obtained composite castings were evaluated in terms of the degree of alloy saturation and the displacement of carbon fibers. As a result of the conducted tests, it was found that as a result of unfavorable arrangement of fibers in the CF preform, the flow of metal may be blocked and porosity may appear in the casting. [ABSTRACT FROM AUTHOR]

Systematic studies of the influence and interrelation of the temperature and physicotechnological factors on the crystallization and formation of structural zones in steel castings are carried out. Therefore, research aimed at determining the boundaries of the optimal influence of the thermal and technological factors on the processes of crystallization and structural formation of steels is important for further use of the regularities of the formation of structural zones in castings to optimize their macro- and microstructures and physical and mechanical properties. Changing the temperature--time conditions of crystallization and post-crystallization cooling allows for regulating the processes of forming the structure of steel castings. The phase-structural state and properties of steel in different structural zones of castings depend not only on the technological parameters of casting and crystallization, but can also be intentionally modified by regulating the conditions of solidification and structure formation. The study investigates the patterns of forming the main macrostructural zones across the section of castings of carbon hypoeutectoid steels and the quantitative changes of their length depending on the thermokinetic conditions of crystallization. [ABSTRACT FROM AUTHOR]

An analysis of the state of foundry production in the world is presented, as well as an analysis of the state of foundry production in the Republic of Belarus. The dynamics of changes in production capacities, the degree of loading and the volume of production of castings for various types of alloys is shown. It is established that the structure of cast products produced both in the world and in the Republic of Belarus is in constant dynamics and there is a constant change in the ratio of production volumes from various alloys. The development of the foundry production of the Republic of Belarus as a whole is similar to the world foundry production, however, there is a certain time lag and certain differences in the ratio for different types of casting.

It is shown that hydrogen is a demodifying element of the structure of cast magnesium alloys during their crystallization. Hydrogen atoms, adsorbing on elementary nanocrystals in melts, prevent the combination of nanocrystals into the nucleus of crystallization of α‑phase microcrystals. As a result, molds with an unmodified structure are formed. Modifiers reduce the concentration of adsorbed hydrogen in the melts of magnesium alloys. This results in the milling of α‑phase microcrystals in castings as they solidify.

A technique that allows calculating the values of the specific heat flux in a given range of values of the technological parameters of casting and the maximum allowable thickness of the casting crust at the outlet of the mold is proposed. The information on the temperature regime of the mold at various casting parameters can serve as a database containing the necessary information to solve the casting solidification problems. With the subsequent design of tooling and equipment, there is no need for additional experimental studies and analysis of the results obtained.

It has been shown that hydrogen and oxygen atoms cannot be present in the open pores of crystal lattices of base metals of casting alloys. The solubility of gases in liquid casting alloys is a nanostructured process. Hydrogen and oxygen atoms in melts are adsorbed by basic metal elemental nanocrystals. Nitrogen dissolves in liquid iron, nickel and chromium not in atomic form, but in the composition of elementary nanocrystals and nitride molecules. After deoxidation of molten casting alloys, the main gas dissolved in them is hydrogen.

Modern technology demands have raised the popularity of aluminum metal matrix composites (AMMCs) as it best suits diverse industrial applications. The need to develop an advanced functional material for specific applications attracts global researchers. Commercial needs for cost-effectiveness, quality improvement, superior performance and high strength to low weight ratio are met by composites. Mass production of AMMCs for specific industrial applications prefer stir casting as a simple and cost-effective manufacturing method. In addition, the production of composites turn more economic by reducing the weight percentage of ceramics and adding natural fibers either in the form of fibers, milled powder or ash to achieve the targeted properties. Process parameters being a dominating factor for minimal defect composites, their effect on final cast products are discussed along with strengthening mechanisms. This paper also discusses the applications, challenges and future scope of natural fiber reinforced AMMCs. [ABSTRACT FROM AUTHOR]

Ferritic high-Si ductile cast irons replace an unstable mixed ferrite-pearlite matrix with a unique combination of high elongation, strength and hardness (ideal for automotive drive train components) and resistance to oxidation and corrosion at high temperatures (automotive exhaust and turbocharger systems). The present paper analyses the graphite parameters of 4.5%Si, un-inoculated ductile cast iron (4.7%CE, 0.035%Mgres) as an effect of the casting section size. The structure is characterized by 10.5–11.2% graphite and 464–975 nodules/mm2, at more than 70% ferrite and no carbides, including at 3 mm wall thickness. The lower the wall thickness is, the higher the nodule count is and, consequently, the higher the ferrite amount is. The Roundness Graphite Shape Factor (RSF = 0.65–0.68) illustrates the presence of Slightly Irregular Spheroidal Graphite (Form V ISO 945). There is a big difference between the graphite nodularity evaluated according to ISO 16112:2017 [CGI] (NG1 = 79–86%) and according to ISO 945-4-2019 (DI) (NG2 = 65.2–74.6%), both of them based on RSF. Graphite Nodularity (NG3), calculated with the ISO 945-4-2019 [DI] formula, but replacing RSF with SSF, Sphericity Graphite Shape Factor, has an intermediary position. The higher the imposed minimum RSF or SSF is, the lower the Graphite Nodularity (NG4, NG5): 80–90% for min. 0.50 (minimum Form IV or Intermediate Graphite), 60–80% for min. 0.60–0.65 (minimum Form V graphite) and 35–70% for min. 0.80 (minimum Form VI graphite). The SSF is more representative than the RSF for Si-alloyed ductile cast iron, so it is recommended to use a graphite nodularity calculus considering SSF instead of the RSF formula (stipulated by ISO 945-4-2019), with SSF replacing RSF. [ABSTRACT FROM AUTHOR]

Uncoated high-strength alloy steel cap screws retaining a cast aluminum (356.0) diffuser assembly in a centrifugal refrigerant compressor failed in a brittle manner a short time after the system was placed in operation. Evidence obtained during the failure analysis indicated that the failures were the result of hydrogen embrittlement produced by galvanic corrosion and attendant evolution of hydrogen at the dissimilar junction, which was also the site of the highest tensile stress. Suggested measures for minimizing recurrences included use of lower-strength, galvanically-compatible fasteners and appropriately-applied and treated compatible coatings. [ABSTRACT FROM AUTHOR]

The experience of the Physico-technical Institute (PhTI) of the National Acdemy of Sciences of Belarus in the harmonization of international standard ISO 17804 (Founding – Ausferritic spheroidal graphite cast irons – Classification) and development of the Belorussian analogue STB ISO is described. The reasons for the choice of austempered ductile iron (ADI) as an object for standard harmonization are presented: it is the most promising cast iron in comparison with gray and classical ductile iron. The work procedure on harmonization is described: how to include the task into the State Plan on standardization, specificity of translation of the text, peculiarities of with state organizations responsible for approbation of standards such as Belorussian Institute for Standardization and Certification (BelGISS) and State Committee on Standards (Gosstandart), writing a summary of external reviews, working with critical comments from potential users. It is outlined that any foreign standard does not exists independently but is closely connected with at least 10 to 20 other standards. Thus, harmonization necessitates coordination with other standards and sometimes even with handbooks by adding annexes to the main text. The importance of a proper choice of the standard status is outlined: identical (ID) or modified (MOD). Developing an identical standard is prestigious but difficult because is requires harmonization of all the referenced standards, which is a very labor-consuming procedure. It is argued that the most suitable is ‘intermediate’ variant: adopting the authentic text of the international standard (in high-quality translation) but with annexes reflecting national specificity in this area. As a result, a harmonized standard is developed which, for the first time in Belarus, standardize the tensile strength of 800 MPa in combination with the elongation of 10 % and the tensile strength of 1400 MPa in combination with the elongation of 1 % for cast irons.The annual demand for ADI in Belarus is estimated as about 10,000 ton. It is shown that in Belarus, where about 60 industrial enterprises have a foundry and almost every engineering plant has a heat-treatment shop, austempered ductile cast (ADI), which features a high strength, can successfully compete with rolled steel in certain applications.

The size of defects in castings affects mechanical properties such as fatigue strength. These properties are the most important properties used for designing aluminum alloy casting components, and usually increase with decreasing size of internal defects. Large internal defects mainly form due to the volumetric shrinkage of melt at the last solidified position. In this study, we therefore examined the possibility of generating microbubbles in aluminum alloy melts for dispersing internal defects in castings. Ultrasonic treatment was used for generating nitrogen or argon microbubbles in the melt and was found to be suitable for forming fine gas porosities dispersed in castings. The fine gas remained in the melt for 3600 s, and the generated argon gas was detected from the porosities in the castings. The ultrasonic treatment could also remove inclusions and hydrogen in the melt. Moreover, the fine gas porosities in castings did not decreases the tensile strength of the castings. [ABSTRACT FROM AUTHOR]

The effect of heat treatment on the structural-phase state and hardness of small-sized castings made from the Cu-Cr-Al copper alloy obtained by casting in a water-cooled metal mold is studied. Using X-ray diffraction analysis, it was found that the castings consist of a matrix solid solution based on copper. The increased value of the crystal lattice parameter of the copper phase is associated with aluminum atoms dissolved in it. After a low-temperature (450 °C) tempering for 10 hours, the crystal lattice parameter of the matrix solid solution decreases, which is associated with the formation of the Al8Cr5 intermetallic compound on the surface of the casting.It is established that after heat treatment (hardening and tempering), the hardness of castings from the Cu-Cr-Al alloy increases by 1.5 times.

The analysis of the world market of metal castings in 2014–2018 is presented, as well as trends for the short term. The world market of castings from ferrous and non-ferrous metal alloys completed 2018 with a record output of 112.7 million tons, which is 2.6 % more than in the previous 2017. The state of the foundry industry in the countries leading in the world foundry rating is considered. The leaders order of manufacturing countries in 2018 compared to 2014 has changed slightly. China remains the global leader in the world casting market with a share of 43.8 %. The second place with a share of 11.9 % belongs to India, and the third – to the USA (9.5 %). Together, these three countries produced 65.2 % of the world's metal castings. All the "Top-10" countries produced 98.7 million tons of castings, or 87.5 % of global production. In the industry of China, the largest contributors to the production of castings in 2018 were automotive (30 %), cast pipe production (17 %), and the engineering and agricultural machinery industry (11 %). Given the global trends of Industry 4.0 and environmental problems, Chinese foundry workers focused on such areas as casting ecology, automation, digitalization of casting processes and its innovativeness. To protect the environment, the Chinese government has set limits on particulate emissions from gas furnaces. The trends in the context of cast alloys are reviewed and analyzed. There have been tendencies for the displacement of ferrous alloys by light and non-ferrous alloys, as well as the creation of high-strength multiphase alloys for lightweight cast structures, including those with heat treatment. The review outlines the main sections of innovative projects and scientific and technological topics in the foundry and metallurgical industry. A massive transition to the production of electric vehicles will lead to a rather significant decrease in the use of cast iron in the production of engines and at the same time will increase the use of aluminum alloys in the automotive industry.

Hadfield steels are materials with high wear resistance used in the construction of parts that work in abrasive friction, high pressures and mechanical shock conditions. Four experimental samples, obtained from commercial T105Mn120 steel, were subjected to isothermal dynamic mechanical analysis in strain sweep mode (DMA-SS), by means of a dual cantilever specimen holder, at two temperatures, − 40 and + 50°C, with two SS frequencies: 0.5 and 16.66 Hz. These temperatures and frequencies correspond to the extreme conditions encountered during railway exploitation, being caused by environmental temperature or wagon wheel speed, respectively. The samples were work hardened through dynamic loadings and present different surface profilometries. Wear tests were carried out, and mean friction coefficient was determined based on friction torque measurements. Prior and after wear test, surface morphology was analyzed using scanning electron microscopy coupled with energy dispersive spectroscopy and micro-hardness determinations. The results indicate that the tested samples underwent work hardening through a wear mechanism that can explain the remarkable surface resistance of these executive elements of railway safety systems cast from Hadfield steel. [ABSTRACT FROM AUTHOR]

Good quality in composite castings can be confirmed primarily by their user. The producer is obliged to create a good product that meets the user's needs that should undergo quality control. Omission of technological procedures and improper quality control may result in various defects like porosity. This paper presents the characteristics of the casting defect, namely porosity, with a particular focus on porosity in suspension and saturated metal composites. This defect is different, specific to composite castings, making its identification very difficult. The aim of the study is to detect and describe porosity in composites with the use of microscopic and submicroscopic examinations. The assessment of the porosity of the microstructure of composite castings allowed for the formulation of the following conclusions: in addition to the porosity that occurs in castings of classic materials (cast steel, cast iron, and non-ferrous metal alloys), metal composites also distinguish between primary and secondary agglomerates, leaving the reinforcement space not filled, occluded bubbles, and separated gas bubbles. [ABSTRACT FROM AUTHOR]

Thermodynamic calculation of formation of spherical gas bubbles different in water – wetting on flat surfaces by metal melt is made. This process consists of two stages. The first stage is formation of equilibrium gas bubble in the form of ball segment. The second stage is its swinging into a spherical bubble. Calculations were made for gas bubbles with constant volume. It is shown that Gibbs energy of spherical gas bubble formation on water – wetting metal melt substrate is three times less than on nonwettable melt substrate. Thus, gases released by solidification of the castings will preferably be formed and removed as bubbles on the molten metal surfaces of the crystallizable phases of the alloys and directly affect on their microstructure.