Search Results (16)

The structure and phase composition of a eutectic silumin surface layer modified by compression plasma flow impact were investigated in this work. Plasma flows were generated by a magnetoplasma compressor of a compact geometry in a nitrogen atmosphere. The energy density absorbed by the surface layer was varied in the range of 10–35 J/cm². X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and X-ray microanalysis were used as investigation techniques. It was found that the plasma impact led to the formation of a molten layer with a thickness of up to 50 μm. The layer thickness increased with the growth of the absorbed energy density. Dissolution of the intermetallic compounds and primary silicon crystals occurred as a result. The modified surface layer contained grains of a supersaturated solid silicon solution in aluminum. Grains with sizes of 100–500 nm were separated by interlayers of hypereutectic silumin containing nanocrystalline silicon precipitates. The doping elements of the alloy were concentrated mainly in these interlayers. The plasma impact resulted in a 1.5-fold microhardness increase. Full article

Due to its tendency to increase the power of engines, improving their reliability and operational efficiency, the compression ring in combustion engine pistons is embedded in a cast iron insert, which is subjected to the process of “alfining”. This involves covering the insert with an Al–Si alloy, which increases the iron content. Research has shown that the β-Al₅FeSi phases crystallizing in the area of the insert–piston connection are the main cause of an unstable connection between the silumin casting of the piston and the ring insert. Their unfavourable lamellar morphology and large dimensions are the main causes of weakening in the connection between the insert and the piston, resulting in an unacceptable number of defective products. It has also been found that up to approx. 0.59 wt.% Fe, the pore volume fraction is very small (up to 3%), and there is no correlation. However, after exceeding this value, both the volume fraction of the β-Al₅FeSi phase and the number of pores increase monotonically to values of approximately 18% and 14%, respectively, and the correlation between the examined features is statistically significant. These results were compared with known theories of the influence of iron on the porosity of Al–Si alloys, showing that the precipitates of the β-Al₅FeSi phase are more important in the porosity fraction than the two-layer oxide films called “bifilms”. This research was carried out and verified under industrial conditions in one of the largest piston foundries (Federal-Mogul Gorzyce sp. z o.o., F-MG) on a separate line intended for alfining ring inserts intended for combustion pistons. Full article

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

Aluminum-silicon alloys are popular casting alloys. In its raw state, the microstructure of the hypoeutectic silumin consists of a large eutectic β phase against the background of dendritic eutectic α. Due to its large microstructure components, mainly the eutectic β phase, this alloy has low mechanical properties. The unfavorable properties of hypoeutectic silumin can be improved by changing the size and shape of the alloy’s microstructure components. There are several possibilities for controlling the microstructure and the resulting mechanical properties of the alloy. One possibility is to modify the alloy with elements and chemical compounds. This paper presents the effect of phosphorus with Al-Ti-B on the microstructure and mechanical properties of hypoeutectic silumin AlSi7Mg. The proportions of Ti to B were selected on the basis of the results presented in the literature, recognizing the optimal ratio of 5:1. The modifier was introduced into the alloy in the form of an AlTiBP master alloy with a variable content of titanium, boron, and phosphorus. Phosphorus was added at the levels of 0.1, 0.2, and 0.3% of the weight of the modified casting. As a result of the tests carried out, the modifying effect of the introduced master alloy was confirmed. A different morphology of microstructures was obtained for the different chemical compositions of the modifier. The most favorable modification effect, whose measurable parameter is the highest (out of the obtained) mechanical properties, was found for the modifier containing 0.25% Ti + 0.03% B + 0.2% P. It was also found that phosphorus, in the presence of titanium and boron, affects the microstructure and mechanical properties of hypoeutectic silumin AlSi7Mg. Full article

Aluminum–silicon alloys require modification due to their coarse-grained microstructures and resulting low strength properties. So far, research into the modification process has focused on the use of various chemical components and technological processes, the tasks of which are to refine the microstructure and, thus, increase the mechanical properties of the alloy. In this paper, the answer to the question of whether the form of the modifier influences the modification effect of the hypoeutectic silumin will be found. The tests were carried out using the popular silumin AlSi7Mg. To answer our research question, the alloy was modified under comparable conditions using the following elements: Ti, B, and master alloys AlTi1.5 and AlB1.5. Modifiers in the form of Sr and master alloy AlSr1.5 were also used. All mentioned modifiers were produced and introduced into the liquid alloy in the form of a powder and a rod. Master alloys AlSr1.5 were also produced via cooling from the liquid state through cooling in air and the second variant at a speed of 200 °C/s (in the form of powder and a thin strip). The microstructure and mechanical properties were analyzed based on the following measures: tensile strength, elongation, and hardness of silumin. Based on the conducted research, it was found that the form of the modifier also affects the modification effect visible in the form of changes in the microstructure and mechanical properties. For the powder-modified alloy, greater fineness in the eutectic phase (α and B phases) and an increase in all analyzed mechanical properties were obtained. Full article

The core idea of the research consists in a formulation of boundary conditions of a mechanical accelerator pedal’s strength in an Ansys environment, whose conditions are equivalent to full-scale tests under the critical loads defined by the UNECE’s Regulation No. 13. The lack of regulatory requirements for the strength of pedal types other than brake pedals is a major gap in vehicle certification, especially when it comes to agricultural machinery. In such cases, the authors suggest being guided by UNECE R 13 regarding the strength of the accelerator and other types of pedals and checking their behavior under loads of at least 1000 N. The real value of the yield strength of the material (Silumin 4000) is very important, both in the physical real-life experiments and in FEA simulation. The critical case of a short-term shock loading of the pedal in its extreme position has been considered separately. With the help of the Ansys Explicit Dynamics module, results of a pedal’s behavior were obtained; it lost its integrity and suffered destruction. It is also necessary to check the intermediate stress values depending on the loads for direct and hybrid tasks using the Transient Structural module in order to estimate other critical cases of the pedal behavior. Full article

The microhardness and abrasive wear resistance of cast Al-Si alloys after plasma-electrolytic oxidation (PEO) in a weakly alkaline basic electrolyte (3 g/L KOH + 2 g/L Na₂SiO₃), as well as with the addition of H₂O₂, were determined. X-ray analysis showed that the PEO layer comprises two oxide phases, namely α-Al₂O₃ and γ-Al₂O₃, as well as sillimanite -Al₂O₃ · SiO₂ and a small percentage of mullite -3 Al₂O₃ · 2SiO₂. Silicon is present in the structure of the oxide layer, and its percentage is greater than that of the alloys in their initial state. It has been shown that the characteristics of PEO layers on AK9 and AK12 silumins synthesized in an electrolyte of basic composition increase (microhardness up to 900–1000 HV and abrasive wear resistance by 14–57 times). The formation of PEO layers in the base electrolyte with the addition of 3 g/L of hydrogen peroxide intensifies the synthesis process and promotes the formation of high-temperature oxide phases (in particular, corundum). The abrasive wear resistance of both silumins with PEO layers synthesized in such an electrolyte increases by 30–70%. Full article

This paper presents the results of uniaxial tensile tests on specimens of the hypoeutectic aluminum-silicon alloy A319. According to the results, the influence of surface treatment by pulsed electron beam on the mechanical properties of the material was determined. The peculiarities of deformation localization in the material caused by grinding of the surface layer material structure due to rapid crystallization during electron beam treatment were revealed. The surface treatment up to the depth of 100 µm leads to the formation of a fine dendritic columnar structure of silumin and to an increase in the plasticity of the samples. The influence of the surface treatment affects the increase in the deformation localization in the region of the stable concentrator before failure. The greatest increase in ductility and localization of deformation occurs during treatment with an energy density of 15 J/cm². In the process of specimen deformation, unstable, metastable, and stable areas of plastic deformation localization are formed and replaced, and the formation of stable areas of localized plastic deformation, in which the specimen fails at the end of the test, can be detected at the initial stages of testing. In specimens, during the test in the zone of localized plastic deformation, bands are formed which pass through the entire surface of the specimen at an angle of 35 to 55 degrees to the tensile axis, and their development leads to the formation of stable zones of localized plastic deformation and to the failure of the specimen. Full article

This paper presents an original design of a test apparatus for calorimetric measurements of arc efficiency η and melting efficiency η_m in welding processes. The construction and principle of operation of a new flow calorimeter are described, as well as the method for determining the η and η_m values in the process of the surface melting of aluminium–silicon alloy casting surfaces with a concentrated heat flux generated by the TIG (Tungsten Inert Gas) method. The results obtained indicate the advisability of using calorimetric testing to assess the arc efficiency of welding processes. It was demonstrated that changing the welding current and arc scanning speed, as well as changing the chemical composition of the silumin, has an effect on the arc efficiency value η. This has the effect of introducing a different amount of heat into the area of the heated material. The consequence of this is a change in the value of the melting efficiency η_m, which results in a change in the width and depth of the surface melting areas, through this, the cooling conditions of the material. As is well known, this will affect the microstructure of the welds and the width and microstructure of the heat-affected zone, and thus the performance of the welded joints. Full article

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

This paper deals with the determination of the basic corrosion characteristics of metallic materials used as components in car construction to achieve a lighter vehicle with higher rigidity, a more complex “hybrid” of diverse materials is needed for the car body structure. Due to the different types of material used in the manufacture of components and their interactions, the issue of assessing the impact of bimetallic corrosion is currently relevant. Based on the potential difference at the end of the corrosion test, it was possible to determine the “anode index”, which determines the risk of degradation of materials due to bimetallic corrosion. In our case, a hot-galvanized steel sheet/Al alloy EN AW-6060 couple in deicing salt and hot-galvanized steel sheet/steel S355J0 couple in simulated acid rain solution (SARS) has proven to be “safest” and usable even for more aggressive environments. Hot-galvanized steel sheet/Al alloy EN AW-6060 in SARS solution is suitable for slightly aggressive environments. Stainless steel AISI 304/silumin A356 in deicing salt, stainless steel AISI 304/Al alloy EN AW-6060 in deicing salt, and stainless steel AISI 306/Al alloy EN AW-6060 in simulated exhaust gas environment (SEG solution) are not suitable for non-aggressive environments. Full article

This article is devoted to the stress–strain state (SSS) study of metal and reinforced fiber-reinforced concrete beam under static and shock loading, depending on the bimodularity of the material, the mass of the beam, and the location of the reinforcing bars in zones under tension and compression. It is known that many materials have different tensile and compression properties, but in most cases, this is not taken into account. The calculations were carried out by using load-bearing metal beams made of silumin and steel and reinforced concrete beams under the action of a concentrated force applied in the middle of the span. The impact load is considered as the plastic action of an absolutely rigid body on the elastic system, taking into account the hypothesis of proportionality of the dynamic and static characteristics of the stress–strain state of the body. The dependences of the maximum dynamic normal stresses on the number of locations of reinforcing bars in zones under tension and compression, the bimodularity of the material, and the reduced mass of the beam are obtained. A numerical study of SSS for metal and concrete beams has shown that bimodularity allows the prediction of beam deflections and normal stresses more accurately. Full article

Aluminum alloys are widely used to produce automotive components, thanks to their great mechanical properties–to–density ratio. Engine components such as pistons are conventionally produced by casting of Al–Si eutectic alloys (Silumin alloys) such as EN AC 48000. Due to the harsh working conditions and the lower ductility if compared to aluminum–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–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. Full article

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 Fe_xAl_y 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 α was found, together with a transition from a binary plate eutectic composition α(Al) + β(Si) into modified eutectic composition. Full article

A widespread method exerting the influence on the homogeneous formation of the microstructure and enhancement of strength properties of Al-Si alloys is a modification by super- and nanodispersed particles of different chemical compositions. In spite of the significant advances in the studies of the influence of various modifying compositions on the structure and mechanical properties of casted silumins, the literature contains no data about the influence of nanodispersed W-powder on formation of the structural-phase state and mechanical properties of Al-Si alloys. The paper considers the influence of 0.01–0.5 mass % W nanopowder on the structural-phase state and mechanical properties of an Al-12%Si alloy. It has been established that 0.1 mass % of W is an optimal addition. It results in the uniform distribution of eutectic (α-Al + Si), a 1.5-time decrease in the size of the plates of eutectic Si, a change of the shape of coarse plates (coarse plate-like or acicular) into a fine fibrous one, and an enhancement of the mechanical properties by 16–20%. Full article