D16 Aluminum Alloy Research Articles

Impregnation of Graphite with Aluminum under High Pressure

To impregnate graphite of the GMZ brand with liquid aluminum alloy D16, a high-pressure method and apparatus previously used for impregnating carbon frames with liquid coal pitch in the isostatic technology for the production of carbon-carbon composite materials were used. The graphite blank and the amount of aluminum alloy calculated from the initial porosity of graphite were placed in a thin-walled container, degassed in a vacuum furnace, after which the container with the contents was sealed. Thermobaric treatment was carried out at a temperature of 750°C and pressure of 100 and 200 MPa. After finishing the treatment, the density and porosity of the obtained metallographic composites, as well as their compressive strength, were determined. As a result of these thermobaric treatments, the density and compressive strength of the obtained composites increased significantly, and the porosity decreased markedly.

The Tribological Properties of Plasma Electrolytic Oxidation Layers Synthesized on Arc Spray Coatings on Aluminum Alloys in Contact with Various Friction Materials

Oxide layers on the surface of the aluminum alloys D16 and AMg6 and on arc coatings sprayed with electrode wires made of the alloys D16 and AMg6 were synthesized using plasma electrolytic oxidation (PEO). The microstructure, phase composition and micro-hardness of the PEO layers were studied. In addition to the two main phases (α-Al2O3 and γ-Al2O3), a small amount of a metastable crystalized Al2.427O3.64 phase was found in their structure. A comparison was made of the wear resistance and friction coefficients of the synthesized PEO layers during friction tests in pairs with other PEO layers, a galvanic chromium coating, cast iron, steels and bronze of the BrC30 type. The results of the friction tests for the various PEO layers on aluminum alloys in tribo-contact with high-hardness elements made of hardened or chrome-plated steel justify the possibility of their use in a friction pair. We experimentally showed the influence of glycerin additive in motor oil 15W30 on the change in the friction coefficient of the PEO layers synthesized on the aluminum alloys and on the arc-sprayed coatings on their surfaces in tribocouples with hardened steel.

Сравнительный анализ химического состава и механических свойств различных участков сварного соединения дюралюмина, полученного сваркой трением с перемешиванием

Friction stir welding is an advanced method of joining various metals and alloys in the aircraft and mechanical engineering industries. This type of welding is used to join materials that are difficult to weld or not weldable by conventional methods. The high-strength D16 aluminum alloy is difficult to weld by fusion, which is associated with the formation of a dendritic structure in the fusion zone leading to a decrease in the mechanical strength of the joint. In the work, the microstructure and microhardness of a welded seam of the D16 aluminum alloy produced by friction stir welding was studied. Using scanning electron microscopy and optical metallography, the authors identified the presence of three zones: the weld core, the thermomechanical impact zone, and the heat effected zone. In the central part of the welded joint (in the core), a laminated onion ring structure was discovered. A change in the chemical composition of the aluminum solid solution was identified in different areas of the weld zones, as well as the presence of a concentration gradient within each zone. In the upper part of the welded seam, the solid solution is silicon-enriched and depleted in copper. Due to the solid solution depletion in alloying elements, the aluminum content in the solid solution in the zone of the welded joint is higher compared to the initial state. The microhardness values in different areas of the welded joint correlate with changes in the chemical composition. In the welded joint zone, a significant decrease in microhardness was found compared to the initial state, and a change in microhardness associated with the chemical composition gradient within each zone was also observed.

Optical Parameters of Aluminum Alloy Samples Irradiated by High Current Relativistic Electron Beams

The aluminum alloys D16, D16AT are widely used as construction materials in the aircraft industry. Questions connected with the enhancement of the properties of the construction elements made of the alloys through surface modification are of great interest now. The objects of the study in our paper are the samples of the aluminum alloy D16AT subjected to irradiation by high-current relativistic electron beams. Leaving aside the material science aspects, in this work we focused on modeling the optical properties of the samples. The problem is relevant because optical methods for surface analysis have become widespread due to their versatility and efficiency. Through the treatment of the preliminary measured ellipsometry data, we obtain the optical constants of the samples and their dispersion in the visible region of wavelength. The method used consists of an approximation of the reflection coefficient calculated from the ellipsometry data by finding the values of the parameters in the model. The last is performed by the least squares method. The reflection coefficient is assumed to correspond to the semibounded uniaxial medium with the optical axis perpendicular to the interface between the medium and the homogeneous and dielectric ambient medium. The dielectric function of the semibounded medium is approximated by the Drude-Lorentz model. The possibility of birefringence of the samples caused by the irradiation with electron beams is discussed.

Application of microindentation to the evaluation of strain distribution over the section of extruded aluminum alloy bars

The paper proposes to supplement the monitoring of strain uniformity over the cross-section of extruded aluminum alloy bars, based on the macro- and microstructure in the central part, at ½ radius, and in the surface zone in several cross-sections along the length of press products, with microindentation of these sections. For this purpose, the microstructure, the loading diagram, and the pattern of the distribution of micromechanical properties across the cross-section of extruded bars made of the AD33 and D16 aluminum alloys are comparatively analyzed. These alloys differ in that in one alloy, AD33, the alloying elements strengthen the aluminum-based solid solution without forming independent phases, and in the other, D16, they form strengthening intermetallic compounds Al2CuMg. The microhardness of the AD33 alloy is ~55 HV 0.1, that of the D16 alloy being 120 HV 0.1. The alloys differ in the distribution of micromechanical properties over both the transverse and longitudinal sections of the extruded bars. It has been found that maximum homogeneity is characteristic of the central part of the rods made of both alloys. The microindentation data correlate with the changes in the microstructure and the results of assessing the distribution of microstrains in the crystal lattice of an aluminum-based solid solution over the cross-section of extruded products by EBSD using recrystallization maps. This makes it possible to recommend the microindentation method for assessing the distribution of strains over the cross-section of extruded aluminum alloy bars.

The Effect of Laser Shock Peening on the Physical and Mechanical Properties of the Surface Layer of D16 Aluminum Alloy

The Effect of Laser Shock Peening on the Physical and Mechanical Properties of the Surface Layer of D16 Aluminum Alloy

Effect of Heat Treatment on the Structure and Properties of a D16 Aluminum Alloy

Effect of Heat Treatment on the Structure and Properties of a D16 Aluminum Alloy

Protection of aluminum alloys AMg6 and D16 from atmospheric corrosion with aqueous solutions of inhibitors

Protection of aluminum alloys AMg6 and D16 from atmospheric corrosion with aqueous solutions of inhibitors

Chromate-free pigments for anti-corrosion protection of D16 aluminum alloy

Chromate-free pigments for anti-corrosion protection of D16 aluminum alloy

Концепция микромоделирования процесса соединения разнородных материалов пластической деформацией

Introduction. Bond strength between dissimilar materials is the most important characteristic of laminated composites, which determines the success of its development for industrial use. In order to develop the theory of joining materials by plastic deformation, it is proposed to perform computer simulation of joint deformation of representative volumes of dissimilar materials on a microscale and compare the parameters of the stress-strain state with the previously presented theoretical mechanism. The aim of this work is to analyze the stress-strain state of dissimilar materials under plastic deformation on a microscale and to establish the location of the onset of fracture of surface oxide films. To achieve this aim, the following tasks of the work are formulated: 1) to study the surface profiles of dissimilar materials to be bonded by plastic deformation; 2) to simulate by the finite element method (FE) the plastic deformation of contact surfaces of dissimilar materials on a microscale; 3) to study the stages of joint deformation of dissimilar materials on a microscale and verify of the theoretical mechanism. Research methodology. The study of three-dimensional topography and roughness was carried out on a Veeco Wyko NT1100 Optical Profiling System. Deform-3D FE simulation package was chosen as the main research tool. Aluminum alloys AMg3 and D16 were chosen as the materials under study. Results and discussion. In this work, computer FE simulating of the joint deformation of the surface layers of AMg3 and D16 alloys on a microscale was performed, an analysis of the surface profiles of materials after various types of processing was carried out, the parameters of the stress-strain state were studied and compared with the parameters of the theoretical mechanism. Based on the results of the comparison, the adequacy of the proposed theoretical mechanism was assessed, and the practical difficulties of theoretical simulation of the joint deformation of dissimilar materials on the microscale were noted. Microscale FE simulation made it possible to study the flow of plastic deformation in the near-surface layers of materials, as well as to identify areas of the most probable fracture of surface oxide films and, consequently, areas of primary bonding of dissimilar materials.

Вплив швидкості охолодження при кристалізації на структуру сплавів В95 та Д16

It is known that the alloys of the Al-Zn-Mg-Cu and Al-Mg-Cu systems have a very wide crystallization interval (over 100°C) and therefore the technology of roll pouring-rolling of sheet blanks from such alloys has not yet been developed. In this regard, the development of scientific and technological foundations of roll casting for such a range of aluminum alloys is an important scientific and practical task. The purpose of this work is to determine the possibility of aluminum alloys B95 and D16 (crystallization intervals are 160°C and 132°C, respectively) for casting-rolling based on the analysis of the effect of cooling intensity on their structure and mechanical properties. The research was carried out on full-scale samples of B95 and D16 alloys by comparing the obtained experimental values. Determination of the temperature parameters of phase transformations in the studied alloys was carried out using the Derivatograph Q-1500-D device. As a result of the tests, the curves of the differential thermal analysis and the fraction of the liquid phase depending on the temperature were obtained. Based on the results of the research, the suitability of B95 and D16 aluminum alloys for casting and rolling has been substantiated. It was found that the size of α-phase grains for B95 and D16 alloys as the cooling rate increases decreases to 120...200 μm (for cooling rates of 2.5...8.8°С/s), and to 40...70 μm (for cooling rates cooling ~1000°С/s). It has been proven that the hardness of B95 and D16 aluminum alloys mainly depends on the α-phase, therefore, when developing roll casting modes, it is advisable to take into account the hardening features of this structural component (α-phase). At the same time, it should be noted that at the intensity of heat removal, which is typical for roll crystallizers, the obtained sheet blanks from the studied alloys will have dispersed crystal structures with a uniform distribution of phase components along their cross sections. A natural consequence of such primary crystalline structures of cast blanks will be a guaranteed high level of strength characteristics of sheet metal rolled from them. Keywords: cooling rate, alloy, crystallization, structure, phase composition, metal rolling

Fractal analysis of fractograms of aluminum alloys irradiated with high current electron beam

The aluminum alloys D16 and AMg6 were irradiated using the high-current relativistic electron beam in vacuum. Intense electron irradiation of the materials modified their physical properties. The fractal character of the fracture surfaces’ images was studied. The change of the fractality is a distinguished descriptor of the materials modification. The characteristic ductile and brittle fractures are accompanied by the change of the fractal dimension.

Study of Vibration Strength of D16 Aluminum Alloy Joints Welded Applying Resistance Spot Welding

Purpose of research is to develop and test a technique and perform an experimental study of the vibration strength of D16 aluminum alloy joints welded applying resistance spot welding.Methods. Test coupons were made from 1 mm thick D16 aluminum alloy sheet blanks applying resistance spot welding. A feature of the proposed test is the implementation of a symmetrical loading cycle. During the tests, the number of cycles to failure depending on the range of vibrations was recorded. Annealing and thermomechanical straightening were carried out to exclude helical bending after cutout. After deburring and root facing, the surface of the coupons was prepared for welding using chemical etching. The coupons were welded using a TECNA 8214N spot welding machine. The welding current was 30 kA, the welding duration was 0.1 s, the electrodes force was 180 daN. The static shear strength of the welded joint was studied using a UTS 110M-5 1-U tensile testing machine. The breaking force was 3.66 kN. The peculiarity of the proposed test is the implementation of a symmetrical loading cycle. During the tests, the number of cycles to failure depending on the range of vibrations was recorded.Results. As a result of the statistical analysis of the study results, a linear mathematical relationship between the logarithms of the number of cycles to failure and the amplitude of vibrations was obtained. Depending on the range of vibrations, characteristic zones of destruction were revealed. To provide the possibility of comparing the results of vibration obtained under different conditions of fixing the samples, it is proposed to use the range of vibration displacement per unit length of the work[iece as the ordinate.Conclusion. A technique or studying the vibrational strength of joints welded by resistance spot welding under conditions of a symmetrical loading cycle is proposed and tested. For the studied coupons, the equality of the welded joint to the base metal is achieved at the value of the logarithm of the ratio of the range of vibration displacement per unit length of the coupons equal to 0.01.

The effect of lithium on the mechanical properties of alloys in the Al-Li system

The article considers the dependence of wear resistance and hardness on each other on the mechanical properties of alloys in the aluminum-lithium system. In experiments, lithium fluorine compound from A K7 and D16 aluminum alloys was added as alloying elements to obtain an aluminum-lithium sample. Based on the mechanical properties of the samples, the hardness was changed in accordance with the Rockwell method and the abrasiveness was investigated.The samples were poured into a heat-resistant furnace at a temperature of 750 °C.The lithium fluoride compound was introduced into the charge in three different masses. Lithium compound with fluorine was added in an amount of 5%, 10% and up to 15% of the total weight of the charge. Based on the conducted experiments, a graph of the dependence of the hardness of the samples and the wear resistance was compiled.

ON THE SIGNIFICANCE OF SELECTING HYDROPHOBIZATION CONDITIONS FOR OBTAINING STABLE SUPERHYDROPHOBIC COATINGS

A method has been described for obtaining superhydrophobic coatings on the surfaces of tungsten and D16 aluminum alloy using nanosecond laser treatment followed by chemical deposition of fluorooxysilane from a vaporous phase. It has been shown by the examples of aluminum and tungsten that, in order to obtain chemically stable coatings, it is necessary to select sample preparation conditions for applying the hydrophobizer individually for each material. Varying the time of surface pretreatment with oxygen plasma makes it possible to controllably change the density of surface adsorption sites and control the chemical stability of the hydrophobizer layer and, hence, the coating as a whole. Superhydrophobic coatings with contact angles of larger than 170° have been obtained on the studied metals, with contact angles remaining preserved during a long-term continuous contact with aqueous media.

Влияние режимов лазерного ударного упрочнения на физико-механические свойства поверхностного слоя алюминиевого сплава Д16

The effect of laser shock peening modes on the physical and mechanical properties of the surface layer of the D16 aluminum alloy was investigated. Experiments were carried out with different values of laser radiation intensity and with fixed values. The dependences of the maximum deformations and microhardness in the center of the spot on the radiation intensity are obtained. The effect of increasing the laser radiation energy on the plasma expansion process is investigated. As a result, “critical points”were found, after which the nature of the dependences of microhardness and maximum deformations on the intensity of laser radiation changes. It is also concluded that the application of the Fabbro model to simulate the process of laser shock peening with the available assumptions is unreliable

FRICTION PROPERTIES OF MАO COATINGS ON ALUMINUM ALLOYS

Aluminum alloys are widely used in mechanical engineering due to their physical and mechanical properties. However, their low wear resistance and burr resistance limit their use in friction nodes. In this regard, parts made of aluminum alloys operating under conditions of sliding friction require surface strengthening, which determines the friction wear parameters. Research works in this direction allow increasing the reliability and service life of friction nodes. Ensuring the compatibility of friction pairs allows reducing the coefficient of friction and, as a result, to increase wear resistance. One of the effective methods of forming wear-resistant coatings on aluminum alloys is the method of micro-arc oxidation (MAO). The use of micro-arc discharges as highly concentrated energy sources to create conditions for high-temperature electrotechnical processes and phase transformations in the surface layer makes it possible to form structures based on high-temperature oxides on the surface of metals, which provides qualitatively new surface properties: high hardness, wear resistance, corrosion resistance in various environments. However, the use of oxide coatings in bearings is mainly due to their high wear resistance and corrosion resistance. Information on the antifriction properties of aluminum oxide-based coatings is limited. The purpose of this work is to determine the coefficient of friction of MAO-coatings on D16 aluminum alloy in a pair with cast iron, steel and MAO-coating under conditions of oil and water lubrication, and to find out the feasibility of using MAO technology to create sliding bearings. The formation of MAO coatings was carried out in an alkaline-silicate electrolyte in the cathodic-anodic mode. The structure and morphology of the working layer of the MAO-coating surface, which works in friction pairs with cast iron, steel and MAO-coating under conditions of oil and water lubrication, was investigated. The benefit of the available porosity of the working layer of the MAO coating, which is 5-10% and contributes to the retention of lubricant in the friction zone, is shown. The phase composition, hardness of the coatings were studied and the coefficient of sliding friction was determined on the SMC-2 friction machine according to the "disk-pad" scheme when using water and oil as lubricants; the load varied from 0.2 to 2 kN, the nominal pressure from 1 to 11 MPa. It was established that the MAO coating has a crystalline structure, the phase composition is high-temperature modifications of aluminum oxide (α-Al2O3 and γ- Al2O3), and the hardness is 18000-20000 MPa. It was established that the coefficient of sliding friction of gray cast iron - MAO-coating, steel - MAO-coating and MAO on MAO decreases to the value of 0.01 - 0.013 under lubrication conditions. It was found that in a pair of MAO-coating - MAO-coating, anti-friction properties are manifested both under conditions of lubrication with oil and water. The low coefficient of friction for the coating-coating pair in the case of water lubrication is explained by the high hydrophilic properties of the oxide contacting surfaces, which makes it possible to recommend them for use in sliding bearings (liners) of hydroturbines. A conclusion was drawn regarding the reasons for the low coefficient of friction of the studied samples. Keywords: D16 aluminum alloy, cast iron, steel, micro-arc treatment, coating, phase composition, crystal structure, aluminum oxides, coating thickness, coating hardness, friction coefficient, antifriction properties

On Increasing the Stability of Superhydrophobic Layers of Oleic Acid on the Surface of D16 Aluminum Alloy

On Increasing the Stability of Superhydrophobic Layers of Oleic Acid on the Surface of D16 Aluminum Alloy

Influence of technology of biomimetic laser-shock-wave processing of aluminum alloys on their crack resistance and residual fatigue life

The influence of biomimetic laser-shock-wave processing (BLSWP) technology on crack resistance and residual fatigue life of specimens made of D16 aluminum alloy is studied. Biomimetic parameters for BLSWP are determined by analyzing the structure of cherry leaves, on the basis of which a 3D finite element model is developed. It is established that under BLSWP, the stress intensity factors in the samples decrease, which increases their residual fatigue life. Keywords: biomimetics, laser-shock-wave processing, residual stresses, stress intensity factor, crack resistance, crack rotation, D16 aluminum alloy. sakhvadze@mail.ru

Degradation Induced by thermal and chemical impacts on matrix codes installed on brass and aluminium alloy parts by laser

To be securely readable, barcodes and matrix ID codes that are installed on metallic or non-metallic surfaces should be of high contrast both immediately after installation and throughout the life of the product that carries them. However, utilizing the product in hot and harsh environments (in acids, alkalis, etc.) may lead to its structural degradation and, consequently, affect the contrast of the codes making them poorly readable with the help of optical devices. The efficiency of such degradation is also governed by the product material. This paper describes the results of a study that looked at the degradation of matrix codes installed by lasers on products made of L63 brass grade and D16 aluminium alloy following thermal and chemical impacts. It is shown that the thermal resistance temperature of laser-installed ID codes for brass is 200 oC, while barcodes installed on the aluminium alloy remain readable when heated up to 600 oC. A major change is noted with regard to the effect produced by 2% acid solutions on codes installed on brass. In the case of the aluminium alloy, a 2% solution of sulphuric acid did not affect the contrast of the codes. When treated with alkaline solutions, a brass surface with a code turned dark, the contrast of the codes degraded significantly and the code became poorly readable. At the same time, alkali produced but a slight effect on the contrast of codes installed on the aluminium alloy.