Liquid Aluminum Alloys 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.

Research on hot cracking in laser welding of Al-contaminated CoCrFeMnNi high-entropy alloys

To study the thermal cracking susceptibility of laser-welded CoCrFeMnNi high-entropy alloys, stainless steel and aluminum alloy plates were each used as backing for welding. The microstructure of the weld and morphology of the fracture were examined. In addition, the chemical compositions of the fractures, the interfacial tension between the CoCrFeMnNi high-entropy alloy and liquid aluminum alloy, and the linear expansion coefficient of the CoCrFeMnNi high-entropy alloy were determined. The results show that when stainless steel is used as the base plate, no cracking is apparent in the weld, and the microstructure is made up of dendrites and equiaxed crystals. Conversely, when an aluminum alloy plate is adopted, solidification cracks are seen at the center of the weld, and the microstructure consists of bright polygonal dendrites scattered in a dark gray matrix. In the later stage of solidification, the contact angle between the Al-dominated low-melt liquid metal and the CoCrFeMnNi high-entropy alloy is about 14.6°, which is distributed in the form of a liquid film between the dendrite of the CoCrFeMnNi high-entropy alloy weld, and the linear expansion coefficient of the high-entropy alloy is 23 × 10−6-25 × 10−6 K−1 in the temperature range of 900–1100 K, which is higher than the thermal expansion coefficient of austenitic stainless steel in this range, and the solidification temperature range is 1000–1400K. Therefore, thermal cracks tend to occur during the solidification process.

Quality Control of Liquid Aluminium Alloy Using Thermal Imaging Camera

This paper presents the results of a study on the use of infrared thermography to assess the quality of liquid metal, a basic semi-finished product used in foundry production. EN AC-46000 alloy with the designation AlSi9Cu3(Fe) was used for the study. The crystallization process of the alloy was investigated using the TDA method with a Crystaldigraph device and Optris PI thermal imaging camera. The research describes how to use a thermal imaging camera to assess the quality of aluminium alloys. These alloys, due to their propensity in the liquid state to oxidise and absorb hydrogen, a refining procedure in the melting process. The effects of alloy refining are evaluated during technological tests of hydrogen solubility, density and casting shrinkage. The results presented in this paper showed that there is a statistical correlation between the density of the metal and the temperature values from the thermogram of the sample, obtained during its solidification. The existing correlation makes it possible to develop a thermographic inspection algorithm that allows a fast and non-contact assessment of aluminium alloy quality.

Corrosion Behavior of 10 ppi TAD3D/5A05Al Composite in a Chloride Environment.

This study utilizes desalted and denitrated treated aluminum dross (TAD) as a raw material, along with kaolin and 10 ppi (pores per inch) polyurethane foam as a template. The slurry is converted into an aluminum dross green body with a three-dimensional network structure using the impregnation method. A three-dimensional network aluminum dross ceramic framework (TAD3D) is created at a sintering temperature of 1350 °C. The liquid 5A05 aluminum alloy at a temperature of 950 °C infiltrates into the voids of TAD3D through pressureless infiltration, resulting in TAD3D/5A05Al composite material with an interpenetrating phase composite (IPC) structure. The corrosion behavior of TAD3D/5A05 composite material in sodium chloride solution was examined using the salt spray test (NSS) method. The study shows that the pores of the TAD3D framework, produced by sintering aluminum dross as raw material, are approximately 10 ppi. The bonding between TAD3D and 5A05Al interfaces is dense, with strong interfacial adhesion. The NSS corrosion time ranged from 24 h to 360 h, during which the composite material underwent pitting corrosion, crevice corrosion and self-healing processes. Results from Potentiodynamic Polarization (PDP) and Electrochemical Impedance Spectroscopy (EIS) indicate that, as corrosion progresses, the Ecorr of TAD3D/5A05Al decreases from -0.718 V to -0.786 V, and Icorr decreases from 0.398 μA·cm-2 to 0.141 μA·cm-2. A dense oxide film forms on the surface of the composite material, increasing the anodic Tafel slope and decreasing the cathodic Tafel slope, thus slowing down the rates of cathodic and anodic reactions. Factors such as lower interface corrosion resistance or a relatively weak passivation film at the interface do not significantly diminish the corrosion resistance of TAD3D and 5A05Al. The corrosion resistance of the composite material initially decreases and then increases.

Modeling of Impurities Evaporation Reaction Order in Aluminum Alloys by the Parametric Fitting of the Logistic Function.

Advancements in computer capabilities enable predicting process outcomes that earlier could only be assessed after post-process analyses. In aerospace and automotive industries it is important to predict parts properties before their formation from liquid alloys. In this work, the logistic function was used to predict the evaporation rates of the most detrimental impurities, if the temperature of the liquid aluminum alloy was known. Then, parameters of the logistic function were used to determine the transition points where the reaction order was changing. Samples were heated to 610 °C, 660 °C, 710 °C, and 760 °C for one hour, after which the chemical analyses were performed and evaporation rates were calculated for Cd, Hg, Pb and Zn elements. The pressure inside the encapsulated area was maintained at 0.97 kPa. Whereas parameters that define the evaporation rate increase with the temperature increase, the maximum evaporation rates were deduced from the experimental data and fitted into the logistic function. The elemental evaporation in liquid-aluminum alloys is the best defined by the logistic function, since transitions from the first to zero-order-governed evaporation reactions have nonsymmetrical evaporation rate slopes between the lowest and the highest evaporation rate point.

Steel Ceramic Composites resistant to long-term contact with molten aluminum alloys

The development and evaluation of novel stainless steel-based composites for direct contact with liquid aluminum alloys has been carried out. The Steel Ceramic Composite consisted of 60 vol% 316L stainless steel powder and 40 vol% of MgO or TiO2 ceramic powder. The sample were manufactured using uniaxial pressing and subsequent surface pre-oxidation at 850, 1000 °C for 24 h.The corrosion resistance of composite was investigated against molten AlSi7Mg0.3 alloy using crucible corrosion tests. The tests were carried out at 850 °C for 24 h and 168 h. The influence of pre-oxidation on the corrosion resistance of the samples was analyzed using XRD and SEM/EDS. The corrosion phases formed in the aluminum alloy were investigated using SEM/EDS/EBSD and PSEM/ASPEX/AFA and included the assessment of aluminum alloy contamination by evaluation of corrosion precipitation content, quantity and size. The sample Steel-MgO exhibited excellent corrosion resistance with negligible contamination of the aluminum alloy.

Analysis of the melting and solidification process of aluminum in a mirror furnace using Fiber-Bragg-Grating and numerical models

In the search of an adequate real time strain measurement method in aluminum casting, the use of Fiber-Bragg-Grating (FBG) is being investigated with great interest. In order to do so, the behaviour of glass fiber sensors in a liquid aluminium alloy at temperatures up to 750°C is experimentally analysed in a laboratory environment. For better process understanding a simulation of the fiber alloy composite is conducted. FBG is an optical measurement method, which uses engraved Bragg reflectors in a 125 µm in diameter thick glass fiber. This reflector transmits most of the wavelengths but only reflects one specific wavelength. This specific wavelength can be measured and changes due to the axial strain on the grating by the fluid alloy reaction and by the changes in temperature. Using a so-called mirror furnace, several experiments with the fiber alloy composite are evaluated. These measurements are also the basis for the further understanding of hot tearing. The data gathered during the measurement campaign - both numerical and experimental - is used to parameterize a simulation. As a result, the understanding of the fiber alloy composite behaviour is expanded and a digital twin is modeled with MATLAB’s partial differential equation toolbox.

Activity of strontium in liquid Sr-modified Al-7Si alloy

ABSTRACT In the present study, the Henrian activity coefficient of strontium , dissolved in liquid Al-7Si alloy at 725–730°C has been determined to be in the order of 10−2, using the numerical thermodynamic analyses. By knowing the , formation of the compounds, Sr(OH)2 and SrH2 through the reaction of dissolved elements in Al-7Si alloy melt has been analysed. The results indicated that the free energy of the formation reaction of Sr(OH)2 and SrH2 in the alloy melt are positive at different temperatures, showing that these compounds may not be formed in the liquid aluminium alloys.

Effect of electromagnetic melt mixing on the technological process of aluminium powder production

Effect of electromagnetic melt mixing on the technological process of aluminium powder production

Electrochemical Studies of Stainless Steel and Stainless Steel-TiO2 Composite in Reference to Molten Aluminum Alloy Using a Solid-State BaCO3 Electrolyte.

The influence of TiO2 addition on the high-temperature electrochemical characteristics of stainless-steel-based materials was investigated by means of differential potential measurement, electrochemical polarization and impedance spectroscopy. A new three-electrode approach was utilized which incorporated a liquid aluminum alloy AlSi7Mg0.3 as the reference electrode, barium carbonate BaCO3 as the solid-state electrolyte, and stainless steel or a stainless steel-TiO2 composite as the working electrode. The potential differences between the steel-based working electrodes and the liquid-aluminum-alloy reference electrode were measured for 85 h throughout the whole experiment, including the heating and cooling period. The experiments were performed at 850 °C. The determination of the high-temperature open circuit potential (ECorr) in reference to the liquid aluminum alloy was carried out via potentiodynamic polarization. The polarization-related changes in the impedance characteristics were evaluated by the correlation of impedance responses before and after the polarization. The addition of 40 vol% TiO2 resulted in a reduction in the potential of the steel-TiO2 composite and led to the formation of a more uniform electrode–electrolyte interface. The reaction products on the surface of the working electrodes were investigated by means of SEM/EDS and XRD. They consisted of mixed oxides within the Fe-O, Ba-Fe-O and Ba-Cr-O systems.

Interactions of primary intermetallic compound particles and double oxide films in liquid aluminum alloys

One of the main challenges in processing aluminum alloys in the liquid state is the avoidance of the formation of double oxide films and their incorporation into the final parts. Bifilms in liquid alloys can act as heterogeneous nucleation sites for primary intermetallic compounds (IMCs), which phenomenon can be utilized for their aided sedimentation. In this study, TiAlSi IMCs were used for the sedimentation treatment of a liquid Al–Si–Mg–Cu alloy. The interactions between IMCs and bifilms were studied by computed tomography (CT) and scanning electron microscopy (SEM), while the changes in melt quality were assessed by the CT analysis of reduced pressure test (RPT) samples. Additionally, the grain refinement effect of Ti-addition was studied by grain size measurements. It was found that (Al, Si)3Ti particles became attached to bifilms, and their simultaneous sedimentation resulted in lowered porosity. However, the attachment of IMCs to the surface oxide layer caused Ti-macrosegregation in the top region of the melt. The attachment of (Al, Si)3Ti intermetallic particles is caused by the heterogeneous nucleation of IMCs on oxide films and the partial engulfment of oxide film segments during the growth of the (Al, Si)3Ti particles. Investigations of the pore surfaces support the theory of bifilm-initiated pore formation.

The Effect of Rotary Degassing Treatments with Different Purging Gases on the Double Oxide- and Nitride Film Content of Liquid Aluminum Alloys

Rotary degassing is one of the most frequently used melt treatment technologies used for processing liquid aluminum alloys. Despite this, the information available about the possible effects of this method on the double oxide- and nitride film (bifilm) content, especially when using different purging gases, is quite limited. For this reason, in this study, the effects of multiple rotary degassing treatments conducted with N2 and Ar purging gases on the bifilm quantity of a casting aluminum alloy were compared. The characterization of the melt quality was realized by the computed tomographic (CT) analysis of reduced pressure test (RPT) specimens, image analysis, and scanning electron microscopy (SEM) of the fracture surfaces of K-mold samples. Based on the results, by the application of Ar as a purging gas, relatively low bifilm content can be achieved. On the other hand, while the use of N2 leads to the formation of numerous small-sized nitride bifilms, which significantly increased the pore number density inside the RPT specimens. This can be associated with the nitride formation by the chemical reaction between the liquid aluminum alloy and the N2 purging gas bubbles during the degassing treatments.Graphical abstract

Filtration resistance during pressure filtration tests of liquid aluminium alloys

Abstract Prefil Footprinter, a portable pressure filtration instrument, is usually employed to detect liquid metal quality. However, no investigations have ever been done to determine overall filtration resistance and resistance of the “clean” filter media. Based on the identification of flow behaviour using the derivative methods, classic filtration equations have been effectively used to estimate total filtration resistance for the first time. The variations of overall resistance during filtration provide a new approach to understand filtration behaviour. The resistance values of the “clean” filter media have been obtained for the first time. An innovative method has been developed to obtain the resistance of the “clean”' filter media through the backward extrapolation of the overall filtration resistance versus filtrate weight or filtration time curves over the steady stages operating in incompressible cake mode.

Hydrogen Solubility in Liquid and Solid Pure Aluminum—Critical Review of Measurement Methodologies and Reported Values

Reliable information on the solubility of hydrogen in aluminum and its alloys is critical to the effort of the aluminum industry to control and ameliorate the usually deleterious effects of hydrogen on the properties and performance of pure aluminum and aluminum alloy products. Unfortunately, there is a significant disparity between published values of hydrogen solubility in pure aluminum and aluminum alloys. This is because the measurement of the extremely low soluble hydrogen concentration in aluminum and its alloys is experimentally difficult. Also, the reproducibility, accuracy, and reliability of the hydrogen solubility values are very sensitive to the measurement techniques, test conditions, chemical composition, and state of the aluminum sample. Thus, no serious discussion of the reliability of reported values of hydrogen solubility in aluminum and its alloys can be undertaken without a critical assessment of the fundamental principles of the experimental techniques used in the determination of the reported values. In this article, a critical review of the fundamental principles of the experimental techniques used in the measurement of hydrogen solubility in liquid and solid pure aluminum and aluminum alloys is presented. In addition, the reliability and possible accuracy of reported values of hydrogen solubility in solid and liquid pure aluminum are critically assessed. Empirical equations for calculating hydrogen solubility in liquid and solid pure aluminum as a function of temperature and pressure, derived from the most reliable sets of data are recommended. At 101.3 kPa (1 atm.) hydrogen partial pressure, the most reliable values of hydrogen solubility at the melting point (833 K) of pure aluminum are 0.71 cm3/100g (i.e., 6.32 × 10-5 wt.% H) and 0.043 cm3/100g (i.e., 3.81 × 10-6 wt.% H), in the liquid and solid state, respectively. So, the partition coefficient of hydrogen in pure aluminum is 0.061.

Influence of modification with highly dispersed silicon carbide on the casting properties of the secondary alloy of the Al-Si system

One of the main areas of application of aluminum is the aerospace and transport industries, which are constantly increasing the requirements for the properties of cast products. The use of aluminum as the main material for the manufacture of various parts of vehicles can significantly reduce their weight, which leads to a decrease in fuel consumption. In order to meet the requirements of the modern world, the work considers studies to improve the quality and increase the properties of products from the secondary aluminum alloy AlSi12. Modern technologies for processing liquid aluminum alloy are analyzed. According to the results of an analytical review, it was found that modifiers that affect the size of the primary grain and the shape of inclusions of eutectic silicon are of the greatest interest. It was found that the modification processes do not change the chemical composition of the alloy, but rather contribute to a change in the size and shape of the structural components of the alloy. The paper considers the influence of an ultradispersed SiC modifier with a particle size of up to 200 nm on the casting properties of secondary aluminum alloys: fluidity, linear and volumetric shrinkage. The fluidity was studied in green sand and metal mould. It was found that the addition of 0.1 % SiC improves the fluidity of the secondary alloy from 560 to 630 mm for green sand mould and from 230 to 295 mm for a metal mould due to cleaning from non-metallic inclusions. A further increase in the SiC content to 0.2 % does not lead to an obvious increase in fluidity. The study of linear shrinkage found that increasing the content of the modifier to 0.2 % contributes to its decrease. At the same time, an increase in the pouring temperature of the alloy promotes an increase in the total linear shrinkage, which is associated with the long residence time of the metal in the liquid state. As a result of the rapid crystallization of the melt with additional nucleation centers in the role of which are particles of the ultradispersed modifier, the coefficient of volumetric shrinkage decreases from 28 to 20 %. The proposed technical solutions for the modification of alloys of the secondary alloy AlSi12 can be used in processes that will improve the quality of cast metal products with the economical use of energy resources and materials for its production.

Purification of aluminium-silicon alloy by electromagnetic directional solidification: Degassing and grain refinement

• An electromagnetic directional solidification process was proposed to purify Al alloy. • Grain refinement and degassing were realized simultaneously. • Effects of the induction current, moving rate, and remelting were investigated. • Both tensile strength and elongation were improved by remelting process. • The mechanism of bubble transfer process was explained by simulation. The grain size and porosity are two significant parameters to evaluate the properties of the Al alloy. In this work, an electromagnetic-field-enhanced directional solidification process hybridized with the remelting treatment was proposed to refine the grain size of Al alloys and at the same time to remove the residual gas in molten alloys. Furthermore, the effects of several factors on the grain refinement and degassing were investigated. The high induction current is effective for the obtainment of the small homogeneous grain size because of the stirring effect. With the increase of the moving rate, the grain size increased and then decreased due to the nucleation effect. The remelting process enables both the grain refinement and H 2 degassing to obtain regular grain orientations. The simulated pressure field, velocity field and H 2 gas volume fraction show the mechanism of the bubble transfer in the liquid Aluminum alloy. The pressure field depicts a sharp pressure gradient on the upper side of the bubble. The velocity field indicates an increase in the velocity maximum in the bubble. The shape evolution process of the H 2 bubble shows the effect of the interface tension.

Controlled precipitation of intermetallic (Al,Si)3Ti compound particles on double oxide films in liquid aluminum alloys

Entrained double oxide films, or bifilms, can seriously alter the structural integrity, microstructure, and in this way, the mechanical performance of aluminum alloys. Bifilms, which usually preexist in suspension in the liquid metals, are known to be potential heterogeneous nucleation sites for certain intermetallic phases during the solidification of the alloys. However, the investigations on the possibility of the nucleation of titanium-containing intermetallic phases on double oxide films, the possible effects of this phenomenon on the melt quality, as well as on the resulting microstructure, were absent to date. In this work, a novel melt treatment technique is proposed, which was used to induce the precipitation of (Al,Si) 3 Ti particles in a liquid multicomponent Al Si alloy. Differential thermal analysis (DTA), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) were used to characterize the phases formed during the experiment. SEM-EDS investigations proved that the (Al,Si) 3 Ti intermetallic phase precipitated on MgAl 2 O 4 double oxide films and the wetted side of the surface oxide layer of the melt. As revealed by glow discharge optical emission spectroscopy (GDOES) and optical microscopic investigations of the microstructure, the majority of the precipitated (Al,Si) 3 Ti particles sedimented to the bottom region of the melt. Based on the computed tomographic (CT) analysis of reduced pressure test (RPT) samples, this sedimentation extensively reduced the bifilm content in the upper regions of the melt. The theoretical basis of a new melt treatment technique is laid down. • The heterogeneous nucleation of TiAlSi intermetallics on bifilms was investigated. • A novel, controlled precipitation-based melt treatment technique is proposed. • The sedimentation of TiAlSi compounds can significantly improve melt quality. • Nucleation on the surface oxide layer causes Ti-macrosegregation.

Development of viscosity model for aluminum alloys using BP neural network

Viscosity is one of the important thermophysical properties of liquid aluminum alloys, which influences the characteristics of mold filling and solidification and thus the quality of castings. In this study, 315 sets of experimental viscosity data collected from the literatures were used to develop the viscosity prediction model. Back-propagation (BP) neural network method was adopted, with the melt temperature and mass contents of Al, Si, Fe, Cu, Mn, Mg and Zn solutes as the model input, and the viscosity value as the model output. To improve the model accuracy, the influence of different training algorithms and the number of hidden neurons was studied. The initial weight and bias values were also optimized using genetic algorithm, which considerably improve the model accuracy. The average relative error between the predicted and experimental data is less than 5%, confirming that the optimal model has high prediction accuracy and reliability. The predictions by our model for temperature- and solute content-dependent viscosity of pure Al and binary Al alloys are in very good agreement with the experimental results in the literature, indicating that the developed model has a good prediction accuracy.

Fabrication and characterization of aluminium hybrid metal matrix composite with power chillers

The current tendency is to fabricate an innovative group of MMC term as HMMCs where different combinations of the materials are choosing in the direction of achieve advanced mechanical properties. In this current exploration intend by manufacturing aluminum union/ Silica/Carbon (Al/SiO2/C) HMMC within mould restrain dissimilar Coldness resources through separate constituent part within liquid state aluminum alloy. In this break up particles are additional varieties as of 4 just before 16 wt% into hierarchy of 4 wt%. The prepared cast composites specimens are as per the American Society for Testing and Materials Standards for mechanical properties.

About brownian movement in liquids

It has been shown that Brownian movement in water occurs as a result of elastic collisions of ice nanocrystals with Brownian particles. Water consists of 87 % of ice nanocrystals and 13 % of water molecules. At 300 K, the ice nanocrystal in water on average consists of 24 water molecules. Brownian movement is an experimental confirmation of the nanocrystalline structure of liquids. This concept of liquids is of great importance for the theory of crystallization and modification of alloys. In metallic liquids, Brownian motion refers to microscopic non-metallic particles and intermetallides that have densities comparable to melt densities. In liquid aluminum alloys, Brownian particles are microscopic alumina particles that remain in the castings when they solidify.