Solid Aluminum Research Articles

Enhanced rate of hydrogen production by corrosion of commercial aluminum

Hydrogen has been produced by corrosion of technical grade aluminum Al-6061. Al-6061 is an alloy containing a small percentage of several elements, mainly Mg and Si. It has been verified that this alloy is corroded faster and produces more hydrogen per unit of time than pure aluminum. This result is due to facilitation of corrosion at grain boundaries in aluminum alloys. Hydrogen production rates have been dramatically accelerated by decreasing the size of aluminum particles. Thus Al-6061 turnings have been produced with a lathe and then they were compressed to create porous pellets with a density of 72% compared to solid pure aluminum. These pellets can produce hydrogen in concentrated KOH solutions at very high rates reaching 66.7 ml min−1. This method is safe and reproducible and it may find important application as a means to “store” hydrogen in the form of porous Al-6061 pellets.

Effect of pulsed metal inert gas (pulsed-MIG) and cold metal transfer (CMT) techniques on hydrogen dissolution in wire arc additive manufacturing (WAAM) of aluminium

Aluminium is one of the most experimented metals in the WAAM field owing to a wide range of applications in the automotive sector. Due to concerns over reduction of strength, elimination of porosity from wire arc additive manufactured aluminium is one of the major challenges. In line with this, the current investigation presents findings on hydrogen dissolution in solid aluminium and hydrogen consumed to form porosity along with its distribution as a function of heat inputs and interlayer temperatures in a WAAM 5183 aluminium alloy. Two varieties of WAAM, pulsed metal inert gas (MIG) and cold metal transfer (CMT), were explored. Samples made with pulsed metal inert gas (pulsed-MIG) process picked up more hydrogen compared to samples produced by cold metal transfer technique. Correspondingly, pulsed-MIG samples showed increased number of pores and volume fraction of porosity than samples manufactured using the cold metal transfer (CMT) technique for different heat input and interlayer temperature conditions. However, CMT samples exhibited higher amount of dissolved hydrogen in solid solution compared to pulsed-MIG process. In addition, heat input, interlayer temperature, and interlayer dwell time also played a key role in pore formation and distribution in WAAM-produced aluminium 5183 alloy.

Reactive wetting of metallic/ceramic (Al/α-Al2 O3 ) systems: a parallel molecular dynamics simulation study

The reactive wetting process of a flat solid alumina (α-Al2 O3) ceramic surface by metallic aluminum (Al) nanodroplets with different shapes (spherical, cylindrical, and layer) is studied using parallel molecular dynamics (MD) simulations based on a variable charge MD method, with focuses on heat transfer, mass transfer, and the structure of the reactive region at the Al/α-Al2 O3 interface. We find that the diffusion of oxygen (O) atoms from the substrate into the droplet leads to the formation of a continuous layer of reaction product at the interface. The diffusion length of oxygen atoms into the spherical Al droplet is found to be ~7.3 Å, and the number density of O atoms at the ~5 top layers of the substrate decreases substantially. As a result, the structural correlations near the reactive region differ considerably from those in the solid substrate. Heat generated by the exothermic reactions in the reactive region is transferred to both the substrate and the droplet. The heat transfer is found to be sensitive to droplet shape.

Aluminum–Carbon Interaction at the Aluminum–Graphene and Aluminum–Graphite Interfaces

The interaction of liquid and solid aluminum with the graphene and graphite surfaces is studied using the density functional theory and a molecular dynamics simulation. The Morse potential is parameterized using the results of ab initio calculations in order to describe the interaction between aluminum and carbon atoms. This potential is used to investigate the interaction of a molten aluminum drop with the (0001) graphite surface theoretically. The properties of the free aluminum melt surface and the contact surface formed upon wetting graphite by the molten drop are calculated. The calculation results agree well with the available experimental data.

Study of Calcium Treatment in Steel Ladles for the Modification of Alumina Inclusions to Avoid Nozzle Clogging during Casting

Presence of non-metallic inclusion deteriorates quality of steel and causes nozzle clogging during casting. Nozzle clogging eventually leads to a disruption of normal casting operations. This happens when solid alumina inclusions get accumulate in the nozzle of submerged entry nozzle (SEN). Therefore, it is required to understand the inclusion characteristics (shape, size and chemistry), which forms during the steelmaking process. Calcium is added in the steel ladle furnace (LF) in the form of CaSi wire to modify inclusions and to desulphurize steel. The range in which all the oxides become liquid and no solid sulphides begin to form is regarded as the "optimum window" or “liquid inclusion window” for calcium treatment. It is a target to obtain this calcium addition window, during calcium addition in the ladle furnace. This window mainly depends on the sulfur and total oxygen contents of the liquid steel bath. In the present study, inclusions characteristics such as volume fraction of inclusions, inclusion rating and EDS analysis of inclusions has been carried out using SEM-EDS. Thermodynamic study is carried out using thermodynamic software FACTSAGE and databases to find out formation of various calcium aluminates and the precipitation of CaS. Results show that liquid inclusion window mainly depends mainly on the sulphur level, total oxygen and aluminum content in the steel. These windows will help in calculation of calcium addition range for optimizing the addition of calcium in the ladle. These nomograms have been validated with actual plant condition to reduce the nozzle clogging during continuous casting.

Analysis and improvement of material flow during extrusion process using spreading pocket die for large-size, flat-wide, and multi-ribs profile

Spreading extrusion is an advanced technology to produce the solid aluminum profiles with large-size, flat-wide, and thin-walled structures. Currently, little research has been reported on the hot extrusion process through spreading pocket die for manufacturing these kinds of aluminum profiles. It is a challenging task for die engineers to control the billet through die cavity with a uniform velocity. Reasonable structure design for spreading pocket die can eliminate extrusion defects and improve the performance of extrudate. In this paper, virtual tryout of spreading extrusion process for a large-size, flat-wide, and multi-ribs aluminum profile was performed through arbitrary Lagrangian-Eulerian simulation. Firstly, spreading pocket die was designed based on the theory of metal plastic flowing. The uniformity of flow velocity distribution on the cross-section of die exit was evaluated quantitatively through standard deviation calculation. Then, a series of structure modifications for the spreading pocket die was proposed to improve material flow during die cavity based on the simulated results. Thirdly, a synthetical comparison of extrusion formability for the modified and initial spreading pocket dies was carried out, including the metal flow behavior, exit temperature, residual stress of extrudate, and peak extrusion force. Finally, the modified extrusion dies were manufactured, and corresponding extrusion experiment was performed to verify the effectiveness and reliability of numerical simulations. The key design points of spreading pocket die for large-size, flat-wide, and multi-ribs aluminum profile were concluded.

Modeling the Thermo‐Mechanical‐Chemical Behavior of Condensed Phase Reactive Materials

AbstractEnergetic material condensed phase constituents come into contact, chemically react, and simultaneously undergo a phase change. Phase change in a given molecular material is often considered separately from the chemical reaction. We use a self‐consistent continuum, thermo‐mechanical model based on specified Gibbs potentials for all relevant component species that are present in a single material. A single stress tensor and a single temperature are assumed for the material.Physically‐based mass fractions of the components are used to describe composition and phase and chemical change and replace order parameters used in older phase‐field variable theories. Our formulation is entirely analogous to non‐equilibrium theories used for gas‐phase combustion but generalized to include condensed phases. We describe the formulation and illustrate its use with three examples. Example 1. considers the quasi‐static heating of an oxide‐coated aluminum particle, that is slowly heated so that the temperature within the particle can be considered a constant. We compute the stress and displacement within the particle by using the derived multicomponent equation of state. Example 2. shows how to model the melting and vaporization in a rapidly heated, confined slab of initially solid aluminum. The model treats multi‐phase transitions and illustrates how the multicomponent equation of state is used. Example 3. describes the modeling of mechanical thermo‐chemical ignition processes in a nano‐slab of HMX and considers six components: Two solid (beta and delta HMX), one liquid HMX component, and two gas components for vapor HMX and reacted products. We describe some possible next steps for further study and model improvements and how to interact with modern reactive molecular dynamics.

Dynamic stress-strain response of high-energy ball milled aluminium powder compacts

Ball milling is a bulk powder manufacturing process used in the creation of dispersion strengthened and nanostructured materials. Fundamentally, these powders have not been dynamically characterized in a green state prior to hot consolidation. The understanding of high strain-rate compaction on void collapse and particle interaction for such systems can help the development of predictive models for impact events of porous metallic structures that may be employed as energy absorbers, reactive structures, and intermetallic materials. This study investigates high strain-rate impact of porous green compacts of as-received and high-energy ball milled (HEBM) aluminium powders characterized under dynamic compression using a split-Hopkinson pressure bar (SHPB) in a passive confinement configuration. The plastic deformation of the powder compacts and crush up were shown to be strain-rate insensitive within the strain rate range of 1000–2100 s−1 and as a result, were modelled adequately with a second order P-α model. The as-received aluminium and HEBM aluminium powders appear to have the same strain-hardening coefficient and strength index as solid aluminium after yielding. The respective stress-strain responses of green compacts follow the same trend but differ only in strength as result of porosity and pre-strain experienced prior to dynamic compression. The HEBM powder was found to be twice as strong as the untreated as-received aluminium powder.

A Novel Eddy Current Speed Sensor With a Ferrite E-Core

This letter presents a novel speed sensor based on motion-induced eddy currents in conductive moving parts. The magnetic yoke is an E-shaped ferrite core. The excitation coil is on the center leg of the E-core, and two antiserially connected pick-up coils are on the side legs. Solid iron and aluminum materials are used for the moving part in the simulations and in the measurements. Two-dimensional and 3-D finite element methods are used for a detailed analysis and for the parametric calculations of the eddy current speed sensor. Despite its simple structure, the proposed eddy current speed sensor shows high linearity. The analysis and the measurements are performed at various speeds and excitation frequencies for an evaluation of the performance of the eddy current speed sensor. The minimum linearity error is less than 0.5%.

A study on interfacial activities between Nb and liquid Al in static and dynamic condition

In the present study, an effort has been made to investigate the interfacial activities between the solid Niobium and liquid Aluminium. Aluminium was melted at 750 °C temperature and subsequently, solid niobium was immersed into the liquid aluminium and held for different time intervals. The study was conducted in static as well as dynamic conditions. Temperature and time were similar for both static and dynamic conditions. After solidification, the Nb-Al interface was studied under optical microscopy, scanning electron microscopy, EDS and X-Ray diffraction analyzer. The analysis revealed that there was no change in the dimension of Nb sample and no intermetallic compound formed on the surface or subsurface of solid Niobium under present experimental condition.

Utilisation and Quality Management of Power Plant Fly Ash

Over the past decades, both the residential and industrial energy demand has increased due to the continuously growing consumption and production. As a large share of the electricity is still produced using fossil fuels, the utilisation of the by-products is a contemporary and pervasive issue. Fly ash is generated in large quantities in coal-fired power plants and has been proven to be an appropriate raw material for various industrial uses. Among others, it is applicable as an additive and lightweight aggregate in the cement and concrete industry, can be used for CO2 sequestration, glass foam production, catalyst production, or as a base material for geopolymers, as well. Geopolymers are inorganic polymers produced via the reaction between solid alumina and silica containing or alkali silicate materials in alkali media. Due to their numerous advantageous properties and wide variety of utilisation possibilities, research on fly ash base geopolymers became widespread topic. The quality of fly ash is determined by technical requirements, and the degree of quality control requirements depends on the final use. In certain fields of applications, standards and regulations have already been created to ensure the consistent quality of the final products made from fly ash, e.g. in the cement and concrete industry. There are various methods for fly ash processing, however, the methods to achieve the necessary properties are not standardised.

Utilisation and Quality Management of Power Plant Fly Ash

Over the past decades, both the residential and industrial energy demand has increased due to the continuously growing consumption and production. As a large share of the electricity is still produced using fossil fuels, the utilisation of the by-products is a contemporary and pervasive issue. Fly ash is generated in large quantities in coal-fired power plants and has been proven to be an appropriate raw material for various industrial uses. Among others, it is applicable as an additive and lightweight aggregate in the cement and concrete industry, can be used for CO2 sequestration, glass foam production, catalyst production, or as a base material for geopolymers, as well. Geopolymers are inorganic polymers produced via the reaction between solid alumina and silica containing or alkali silicate materials in alkali media. Due to their numerous advantageous properties and wide variety of utilisation possibilities, research on fly ash base geopolymers became widespread topic. The quality of fly ash is determined by technical requirements, and the degree of quality control requirements depends on the final use. In certain fields of applications, standards and regulations have already been created to ensure the consistent quality of the final products made from fly ash, e.g. in the cement and concrete industry. There are various methods for fly ash processing, however, the methods to achieve the necessary properties are not standardised.

Protective Fabrics: Metal-Organic Framework Textiles for Rapid Photocatalytic Sulfur Mustard Simulant Detoxification

Summary Metal-organic frameworks (MOFs) can catalyze toxic chemical decontamination, but new MOF materials and synthesis strategies are needed to improve performance, particularly in field-usable MOF-textile formats. This article reports for the first time the exceptional photocatalytic reactivity of Al-PMOF (Al-porphyrin-based MOF), composed of an earth-abundant metal-containing Al(OH)O4 cluster bridged by H2TCPP (5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin) chromophores, against the toxic sulfur mustard simulant 2-chloroethyl ethyl sulfide (CEES) under visible-light irradiation. Furthermore, Al-PMOF is strongly immobilized into polymeric fibers via well-controlled Al2O3 solid film conversion using dimethylformamide/water cosolvent. The approach enables a secure integration of conformal Al-PMOF films onto polymer fibers at a relatively low synthesis temperature (120°C). In addition, on a per-unit mass of MOF basis, the surface-bound Al-PMOF films enable extremely rapid CEES detoxification turnover frequency, up to 170 mol CEES mol chromophore − 1 min − 1 , more than 10-fold faster than the best MOF powders and 2-fold better than MOF films reported to date.

Inclusions Absorbed by Slags in Interstitial‐Free Steel Production

The nonmetallic inclusions absorbed by ladle slags during secondary steelmaking operations and in the tundish and mold during casting are crucial to the production of interstitial‐free (IF) steel. However, little to no research has been conducted on the separation and dissolution of inclusions along with a focus on IF steel. Herein, a theoretical study of the separation of solid alumina at the steel–slag interface is conducted. The dissolution of alumina particles is observed in situ in different IF steel slags, and the dissolution mechanism is analyzed. The results show that the interfacial tensions and slag viscosity have a large influence on the predicted displacement, but for IF steel production, the dissolution of inclusions in the slags has a greater influence on the removal of inclusions than on inclusion separation. Using ladle slags with a proper CaO wt%/Al2O3 wt% is the most effective way to remove the Al2O3 inclusions compared with the other slags in IF steel production.

Enhancing the mechanical and tribological properties of solid cylindrical aluminum specimen by reinforcing alumina nanoparticulate through centrifuge casting technique

In this research work, solid composite cylinders of aluminum, reinforced with alumina nanoparticulate have been produced by using centrifuge casting technique, developed at our research center. The microstructure of the cast nanocomposites has been observed under Scanning Electron Microscope (SEM) and the quantitative compositional information has been obtained by using Energy Dispersive X-ray analyzer (EDX). Later, the mechanical and tribological properties of the nanocomposites with different levels of alumina nanoparticulate addition have been studied. The outcomes of the study indicate higher content of alumina nanoparticulate at the top region of the cast specimen as compared with the bottom region. Further, it was observed that, among the various specimens with different alumina nanoparticulate content addition investigated, the cast specimen with 1.5 wt% of alumina nanoparticulate addition improves the mechanical and tribological properties of aluminum.

Simulation of Transport Coefficients of Aerosols and Nanofluids with Hollow Nanoparticles

Diffusion of hollow nanoparticles in low-density and rarefied gases and the viscosity of aerosols with such particles are studied using the previously developed kinetic theory and molecular dynamics method. Nitrogen-based aerosols with hollow and solid aluminum and uranium nanoparticles are considered at a temperature of 300 K and atmospheric pressure. Diameter of the nanoparticles was varied from 5 to 100 nm; the thickness of walls of hollow nanoparticles was 1 nm. It is shown that the diffusion coefficients of hollow nanoparticles always exceed those of solid particles of the same size and the same material, but this difference does not exceed 1%. The viscosity of aerosols with hollow nanoparticles is always lower than of aerosols with solid particles. Using the molecular dynamics method, the diffusion coefficients of hollow and solid nanoparticles of the same diameter and the same material in dense argon are found to be equal.

Application of quantum-statistical methods to studies of thermodynamic and radiative processes in hot dense plasmas

Calculations of thermodynamic and radiative characteristics of hot dense plasmas within different quantum-statistical approaches, such as the use of the Hartree–Fock–Slater model and the ion model, are presented. Calculated equations of state of different substances are used to investigate findings from absolute and relative measurements of the compressibility of solid aluminum samples in strong shock waves. It is shown that our calculated Hugoniot adiabat of aluminum is in a good agreement with experimental data and other theoretical results from first principles. We also present a review of the most important applications of the quantum-statistical approach to the study of radiative properties of hot dense plasmas. It includes the optimization problem of hohlraum wall materials for laser inertial fusion, calculations of the radiative efficiency of complex materials for optically thin plasma in X-pinch, modeling of radiative and gas-dynamic processes in plasma for experiments, where both intense laser and heavy ion beams are used, and temperature diagnostics for X- and Z-pinch plasmas.

Simulation of the energy spectra of swift light ion beams after traversing cylindrical targets: a consistent interpretation of experimental data relevant for hadron therapy

We have performed detailed simulations of the energy spectra, recorded at several angles, of proton and helium ion beams after traversing thin cylindrical targets of different nature (liquid water and ethanol jets, as well as a solid aluminium wire), in order to reproduce a series of measurements intended to assess the stopping power of 0.3–2 MeV ions. The authors of these experiments derived values of the stopping power of liquid water (a quantity essential for the evaluation of radiation effects in materials, particularly for radiotherapy purposes) that are ~10% lower than what is expected from other measurements and theories. In our simulations, instead of treating the stopping power as an unknown free parameter to be determined, we use as input the electronic stopping power accurately calculated within the dielectric formalism. We take into account in the simulations the different interactions that each projectile can experience when moving through the target, such as electronic stopping, nuclear scattering or electron charge-exchange processes. The detailed geometry of the target is also accounted for. We find that our simulated energy distributions are in excellent agreement with the published measurements when the diameter of the cylindrical targets is slightly reduced, what is compatible with the potential evaporation of the liquid jets. On the basis of such an excellent agreement, we validate the accuracy of the model we use to calculate electronic excitation cross sections for ions in condensed matter in its range of applicability (particularly the electronic stopping power) needed for charged particle transport models, and we offer a consistent, but alternative, interpretation for these experiments on ion irradiation of cylindrical targets.

Effect of Specimen Dimensions on Yield Shear Stress in Torsion Testing by using Taguchi Method and GRA

In this paper, investigated the effect of Al 6061 T6 solid specimen dimensions on torsional tests on yield shear stress. Torsion experiments were conducted at various levels of solid aluminum samples using key sample dimensions such as outer diameter, effective length, total length and fillet radius. Taguchi parameter design and optimization approaches are used to design experiments, and then predict the optimal set of parameters. Multi-objective optimization was done using the Grey Relational Analysis (GRA) method. In the GRA method, a grey relational grade is found to determine a set of parameters for multi-objective optimization of parameters. It is found that the outer diameter has a greater effect on the yield shear stress.

Reaction bonding alumina with AlN–SiC solid solution by nitridation of matrix containing Al–Si powders

An AlN–SiC solid solution-bonded alumina composite was successfully synthesized by pre-synthesizing an isostructural AlN mesophase as an induced nucleus at 1600 °C in flowing nitrogen. The phase composition and morphology were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The reaction mechanism is as follows. An AlN cladding is formed on the surface of Al particles by holding the Al–Si–Al2O3 green body at 580 °C for 8 h in N2 atmosphere. As the temperature rises, the AlN cladding ruptures, Al(l) flows out, and entraps the AlN fragments with high reactivity to migrate along the pores, mixing Si(l) and ultra-fine carbon from resin binder in the matrix to form an Al(l)–Si(l)–C(s)–AlN(s) mixture. At 1600 °C, Al(l) and Si(l) preferentially react with trace O2 in nitrogen to form metastable Al2O(g) and SiO(g), which diffuse outward and react with N2 in the peripheral of the brick to form a sheet-like 21R-SiAlON. The 21R-SiAlON sheets interlaced with each other, forming a dense layer. The formation of the dense layer rapidly consumes O2, and the $$P_{{{\text{O}}_{{2}} }}$$ inside the brick is lowered quickly. In such reducing condition, under the induction of the preformed AlN mesophase, the isostructural AlN–SiC solid solution is formed in situ by the reaction between Al(l)–Si(l)–C(s)–AlN(s) mixture and N2, and therefore a non-oxide bonded oxide composite is prepared. The AlN–SiC solid solution-reinforced Al2O3 composite possesses high cold crushing strength of 116–217 MPa.