Aluminum Suspension Research Articles

Sintering of 3D-printed aluminum specimens from the slurry-based binder jetting process

This work investigates a novel method of producing complex-shaped aluminum parts by slurry-based binder jetting and sintering. In this process, a green body is built up by layer-wise deposition of an aqueous aluminum suspension and selective powder bonding by ink-jet printing. The powder bulk generated from the suspension shows an increased density compared to powder-based binder jetting and, thus, a high initial density for the subsequent densification step. This allows for higher final densities and reduced shrinkage. Aluminum is of special interest as it is widely available and of low density but challenging to sinter due to an oxide skin surrounding every particle. The research in this paper investigates the effects of the sintering atmosphere and sintering additives on the microstructure of powder compacts produced by slurry-based binder jetting. The incorporation of magnesium as an additive during the sintering process of aluminum has been found to substantially improve densification during sintering in an argon atmosphere.

The Potential of Cast Stock for the Forging of Aluminum Components within the Automotive Industry

In the automotive industry, there is a drive to reduce environmental impact, energy consumption, and costs related to the manufacturing of forged aluminum suspension components. The replacement of extruded stock with cast forging stock is one option that offers substantial potential for such savings. The casting technology, low-pressure casting (LPC), allows for production of high-quality cast forging stock with minimal surface segregation and smaller diameters than those achieved with traditional casting technologies. This study is a proof-of-principle, conducted to directly compare the microstructure and mechanical properties of LPC and extruded material after forging, through both generic and full-scale industrial forging trials. The results show the advantages of the cast material, including higher robustness against surface grain growth after forging and a positive correlation between mechanical properties, both strength and ductility and the introduction of plastic deformation. Overall, the work demonstrates how forged aluminum components produced from LPC forging stock can achieve mechanical properties and performance, on par with extruded forging stock, showcasing industrial relevance through the production of a safety-critical automotive component.

Electrochemical Formation of “Al–Ni” Composite Coatings from Aluminum Suspension in an Electrolyte Based on a Deep Eutectic Solvent

Electrochemical Formation of “Al–Ni” Composite Coatings from Aluminum Suspension in an Electrolyte Based on a Deep Eutectic Solvent

Analyzing suspension upright of a Formula Society of Automotive Engineers style vehicle.

This project was aimed at modelling the stress and deformation profile of a 6061-T6 aluminium suspension upright of a formula society of automotive engineers style vehicle with a double wishbone suspension under the loading conditions of a 1.5G corner. With these results, it would need to be determined whether the design is fit for use. Using remote displacement boundary conditions for the upper and lower wishbone connections and the control arm connection with a remote force at the centre of the wheel patch acting on the bearing surfaces the maximum stress, overall stress profile and maximum deformation of the upright was calculated. These results after, undertaking a verification and validation study, were a maximum equivalent von-Mises stress of 87.358MPa and a maximum bearing surface deflection of 0.21 mm. The maximum von-Mises stress calculated was less than the fatigue limit of 90MPa signalling infinite life and also less than the yield stress of 240MPa signalling a safe design. Verification and validation techniques were used to ensure the final result was accurate and reflected the real – life system. Structural error was used to verify the results where it was found that maximum structural error in the upright was 0.052mJ and at the location of maximum stress was between 0.0058-1.0782e-8 mJ. Validation of the model was achieved by comparing the reaction forces calculated in ANSYS to theoretical values and was found that the magnitudes were within 2.5% of the theoretical values, thus the model was considered valid.

Two-phase reaction model of a gas-aluminum particles mixture detonation

ABSTRACT The reaction model of aluminum particles is the key to successfully simulate the two-phase detonation of aluminum suspensions. In this study, by considering the decomposition of the aluminum oxide (Al2O3) product at high temperature, the reaction model for aluminum particles is improved and is incorporated into the numerical code. Then numerical simulations for two-phase detonations of Al/air mixtures and Al/O2 mixtures are performed, respectively, the simulated results for the peak pressure and the speed of the two-phase detonation wave are in agreement with the experimental results, which demonstrate the validity of the improved aluminum reaction model. Moreover, the detonation parameters and the distributions of the physical quantities around the detonation wave are analyzed.

Propagation of cellular detonation in a gas suspension in the presence of a concentration gradient

Models for the description of detonation flows in inhomogeneous gas particle mixtures are presented. The physical and mathematical model of heterogeneous detonation of aluminum suspensions is based on approaches to the mechanics of heterogeneous media and semi-empirical laws of ignition and combustion of particles. The model is extended for suspensions that are inhomogeneous in particle concentrations. This suggests the solution of an additional equation for the spatial distribution of initial concentrations. The dependence of the integral heat release of chemical reactions and the fraction of unburned particles on the initial composition is determined from the solution of the stationary problem of the structure of the detonation wave and its agreement with empirical data on the rate of normal detonation. The model for describing detonation in mixtures of reacting gases with inert particles is based on an analysis of the state of chemical equilibrium. The problem of the initiation and development of cellular detonation in a flat channel in the presence of a longitudinal or transverse gradient of the concentration of aluminium particles is considered. The limits of changes in concentrations from poor to super stoichiometric compositions are considered for 1 μm particles. When detonation propagates along a channel with a longitudinal positive (negative) concentration gradient, the cellular structures do not change, but the average and peak values of pressure and phase density increase (decrease). With a transverse concentration gradient, cell-like structures with a curved front, asymmetric and strongly elongated cells form in the channel. The results are consistent with studies of similar gas detonation flows.

Plasticity of Highly Concentrated Suspensions

The rheological properties of aluminum suspensions in low-molecular-weight poly(ethylene glycol) have been systematically studied within a wide range of concentrations up to the ultimate content of the solid phase (about 70%). As the concentration of dispersed particles is increased, the rheological properties evolve from a Newtonian fluid to an elastoplastic solid. In the region of the flowable state, the studied dispersions have no yield stress. However, above a certain concentration, which is considered to be a mechanical glass transition, the suspensions become non-flowable. At higher concentrations, a region of elastoplastic state of highly concentrated systems arises, which has not yet been considered as we know. The boundaries of this region have been determined and the dependences of the characteristics of elasticity and plasticity on stress have been obtained. This region corresponds to the ultimate degrees of filling and is of importance for contemporary additive technologies and so-called “powder injection molding .”

Thermally induced optical nonlinearity in colloidal alloy nanoparticles synthesized by laser ablation

Colloidal suspension of alloy nanoparticles has been prepared and their third-order nonlinear optical response was investigated by means of the Z-scan technique, employing 532 nm continuous wave laser excitation. Alloys colloidal suspension of industrial grade brass, aluminium, and copper was prepared via laser ablation in liquid technique. FESEM analysis reveals the particles size of less than 102.33 nm on average. The magnitude and sign of the nonlinear refraction, n2 and nonlinear absorption, β were determined. It was observed from the closed aperture Z-scan that all the suspensions exhibited a self-focusing effect with a negative nonlinear refractive index, n2, attributed to thermal lensing effect. Colloids of brass possess highest n2 followed by copper and aluminium suspension, attributed to the thermally agitated process whereby heat is transferred into non-local region of the propagation axis. Open Z-scan results revealed that the brass suspension exhibited saturable absorption (SA) with significant negative β value. Aluminium and copper alloy NPs suspension rather shows reverse saturable absorption with a positive β value. These materials were found to exhibit significant nonlinear refraction and nonlinear absorption behaviour, making them possible candidates for photonic and/or optoelectronic applications, especially with low powered continuous wave laser excitation.

Sparkplug ignition of mono- and bi-dispersed aluminum-air suspensions

In the present paper we numerically investigate the problem of spark ignition of monodispersed and bi-dispersed aluminum suspension in the air. The aim of the research is to determine the critical ignition conditions for an aluminum suspension depending on the size and mass concentration of the particles and the fraction distribution. The mathematical formulation of the problem is determined by a system of equations written in a cylindrical coordinate system, consisting of the gas continuity equation, the momentum and energy conservation equations for the gas and particles, oxygen and particles mass balance equations, the particle number density equation and the gas state equation. To solve the problem numerically we use the algorithms of arbitrary discontinuity decay and disintegration of a discontinuity in a medium devoid of its own pressure. We conduct parametric study on the minimum spark energy which is required to ignite the mixture and provide the subsequent steady propagation of the flame in the aluminum-air suspension.

An influence of expressions for thermophysical parameters on calculation results of melting and detonation combustion of aluminum suspensions

The influence of the method for determining the specific heat coefficient on the processes of aluminium melting and propagation of heterogeneous detonation in a mixture of gas and ultrafine aluminum particles is analyzed. Melting process is described within the phenomenological approach for particles with a radius of 6 and 15 nm. An insignificant effect of the relation between the heat capacity and the particle temperature and radius on melting time and temperature distribution inside the particle has been established. The detonation process is studied for stoichiometric suspensions of 50-nm and 1-µm aluminum particles, taking into account the transition from diffusion to kinetic regime of combustion with decreasing particle size. An insignificant influence of the specific heat coefficient representations on the results of detonation structure calculations is established for nanoparticles. For micron aluminum particle suspensions, the 20% difference in the Chapman-Jouguet pressure has been obtained.

Modeling the detonation propagation in nanodisperse mixture of aluminum particles in channels with expansion

The problem of detonation propagrtion in channels with linear expansion filled with nano-sized alumunium mixture dispersed in oxigen was investigated. Transition from diffusion to kinetic regime of combustion with variation of the activation energy was taken into account in the description of the chemical reactions. Specific features of detonation failing in subcritical regimes and propagation in critical regimes have been revealed. The detonation propagation was found to be more unstable then in microdisperse aluminum suspensions.

Development of fatigue analytical model of automotive dynamic parts made of semi-solid aluminum alloys

Abstract Automotive suspension control arm is used to join the steering knuckle to the vehicle frame. Its main function is to provide stability under fatigue stresses of loading and unloading in accelerating and braking. Conventionally, these parts were made of steel; however, fuel consumption and emission of polluting gases are strongly dependent on car weight. Recently, there is a try to develop and design much lighter and better fatigue resistant metal of semisolid A357 aluminum alloys. This work aims at a better understanding of identifying the fatigue strain-hardening parameters used for determining fatigue characteristics of aluminum suspension control arm using analytical and mathematical modeling. The most judicious method is to perform the fatigue tests on standardized test pieces and then plot two Wohler curves, mainly number of cycles as a function of the stress and as a function of the deformation. From these curves and following a certain mathematical and analytical methods, certain curves are plotted and then all of these coefficients are drawn. The new calculated parameters showed a clear improvement of the fatigue curve towards the experimental curve performed on the samples of aluminum alloy A357 compared with the same analytical curve for the same alloy.

Optimization of Casting Design Parameters on Fabrication of Reliable Semi-Solid Aluminum Suspension Control Arm

The semi-solid casting process has the advantage of providing reliable mechanical aluminum parts that work continuously in dynamic as control arm of the suspension system in automotive vehicles. The quality performance of dynamic control arm is related to casting mold and gating system designs that affect the fluidity of semi-solid metal during filling the mold. Therefore, this study focuses on improvement in mechanical performance, depending on material characterization, and casting design optimization, of suspension control arms made of A357 aluminum semi-solid alloys. Mechanical and design analyses, applied on the suspension arm, showed the occurrence of mechanical failures at unexpected weak points. Metallurgical analysis showed that the main reason lies in the difficult flow of semi-solid paste through the thin thicknesses of a complex geometry. A design modification procedure is applied to the geometry of the suspension arm to avoid this problem and to improve its quality performance. The design modification of parts was carried out by using SolidWorks design software, evaluation of constraints with ABAQUS, and simulation of flow with ProCast software. The proposed designs showed that the modified suspension arm, without ribs and with a central canvas designed as Z, is considered as a perfect casting design showing an increase in the structural strength of the component. In this case, maximum von Mises stress is 199 MPa that is below the yield strength of the material. The modified casting mold design shows a high uniformity and minim turbulence of molten metal flow during semi-solid casting process.

Tribologic analyses of a self-mated aluminium contact used for overhead transmission lines

The lifetime of aluminium components is often limited to their poor wear resistance. One example for such aluminium applications are overhead transmission lines. The sore points of these lines are the segments where the aluminium conductors are fixed to the line supports. The fixation is commonly realized via aluminium suspension clamps. Here, a superposition of different loads like traction and bending stresses, clamping forces and different types of wear occurs. To investigate the wear behaviour in these peculiar points, tribologic model tests were carried out. Within the tests, overhead conductor wires and aluminium plates, extracted from suspension clamps were reciprocally slid against aluminium plates (cylinder-on-plate test). The COF and a wear related parameter were recorded constantly. Subsequently, the loaded surfaces were analysed using confocal laser and electron scanning microscopy as well as energy dispersive X-ray spectroscopy. The investigation detected the formation of an oxidized tribologic layer between both components. The tribolayer, which mayor part adhered on the suspension clamps, was mostly formed from material removed from the conductor wires.

Emission and laser absorption spectroscopy of flat flames in aluminum suspensions

Imaging emission spectroscopy, spatially resolved laser-absorption spectroscopy, and particle image velocimetry (PIV) are applied to a flat flame stabilized in a suspension of micron-sized aluminum. The results from the combination of diagnostics are used to infer the combustion regime of the particles and to estimate the characteristic combustion time of the suspension. It is observed that the reaction zone of the flame in stoichiometric aluminum–air suspensions exhibits strong self-reversal of the atomic aluminum emission lines. These lines also exhibit high optical depths in both emission and absorption spectroscopy. The strong self-reversal and high optical depths indicate high concentrations of aluminum vapor within the reaction zone of the flame at multiple temperatures. These features provide evidence of the formation of vapor-phase micro-diffusion flames around the individual particles in the suspension. In aluminum–methane–air flames, the lack of self-reversal and lower optical depths of the aluminum atomic lines indicate the absence of vapor-phase micro-diffusion flames, and point to a more heterogeneous, and likely kinetically-controlled, particle combustion regime. The reaction zone thickness is estimated from the spatially resolved profiles of aluminum resonance lines in both absorption and emission through the flame. The emission measurements yield a reaction zone thickness on the order of 1.7±0.3 mm in aluminum–air flames, and the absorption measurements yield a thickness on the order of 2.3±0.5. It is demonstrated that the combination of the combustion zone thickness measurement, flame temperatures determined from molecular AlO emission spectra, and particle velocity measurements from the PIV diagnostic permits an estimation of the burning time in the suspension. The burning time in stoichiometric aluminum–air suspensions using the suite of diagnostics is estimated to be on the order of 0.7 ms.

The Discrete Regime of Flame Propagation in Metal Particulate Clouds

ABSTRACTFlame propagation in lean suspensions of nonvolatile fuels (aluminum and iron) in oxidizing atmospheres is experimentally investigated. Suspensions of micron-sized fuel particles were dispersed in glass tubes using a flow of oxygen/argon mixture, and flame propagation into a quiescent mixture was observed via a variety of techniques. An independence of flame speed on oxygen concentration (from 15% to 30% oxygen in argon) was observed for the suspensions of aluminum particulates. This result is found to be consistent with theoretical estimations of the relative magnitudes of the particle combustion time and the inter-particle heat diffusion time, suggesting that flame propagation through the aluminum suspensions occurs in a regime controlled by the spatial discreteness of the multiphase medium. Experiments with iron exhibited the expected square root dependence of flame speed on oxygen concentration (from 15% to 60% oxygen in argon), demonstrating that propagation in this mixture is in the classical, continuum regime of thermal flames. The aluminum mixtures also exhibited an array of flame instabilities, including a pulsating oscillation that is theoretically predicted for mixtures with a high Lewis number, although acoustic interactions with the flame tube could not be ruled out in influencing the pulsations. The result that lean aluminum flames propagate in a discrete regime suggests that the statistical nature of the particulate suspensions will have a significant influence on flame propagation, giving rise to percolation-like behavior seen in previous computational simulations of reactive waves in discrete media.

Flame speed measurements in aluminum suspensions using a counterflow burner

The burning velocity is a fundamental parameter in combustion that has been accurately measured with different methods for a variety of gaseous and liquid hydrocarbon fuels. However, it is still unclear whether this concept also applies to the combustion of particulate-fuel suspensions. Attempts to measure the burning velocity in particulate suspensions have been made using a range of experimental techniques, but no study has yet attempted to reconcile the results from different studies. The present work reports the first realization of a stabilized aluminum flame using a counterflow burner. The flow is tracked using Particle Image Velocimetry and the flame speed is obtained as a function of aluminum concentration. The results are then compared to previous data obtained for stabilized flames, spherically-expanding flames, and flames propagating in tubes. The results are in reasonable agreement, given the experimental uncertainties in all of the techniques employed to date, suggesting that the notion of a laminar burning velocity may be applied to suspensions of particulate fuels.

Burning Rate Calculation for a Frozen Nanosized Aluminum Suspension

The paper presents a mathematical model for combustion of a frozen nanosized aluminum suspension (ALICE), taking into account the combustion of aluminum in water vapor, the motion of combustion products, and the velocity lag of particles compared to gas. The model was formulated based on Belyaev’s approach to modeling the combustion of volatile fuels [1]. The burning rate calculated is in agreement with the experimental data on the ALICE burning rate and its variation with pressure.

Monolithic catalysts for hydrogenation of nitrobenzene to aniline: influence of aluminum suspension properties

Aluminum suspensions with different properties were prepared and characterized by UV–Vis spectra, BET, XRD and NH3-TPD. A layer of Al2O3 was coated onto the cordierite monolith by sol–gel method. Pd/Al2O3/cordierite monolith catalysts with the same Pd loading and particle size were prepared, and tested by nitrobenzene hydrogenation under solvent-free conditions. The adsorption of nitrobenzene on acid sites might be the primary effect under the reaction conditions, and a good linear relationship between hydrogenation rate and the acid content of the Al2O3 layer was observed. Furthermore, the stronger acid sites were responsible for the lower aniline selectivity.

Quenching distance of flames in hybrid methane–aluminum mixtures

Quenching distances for laminar flames in hybrid methane–aluminum fuel mixtures (16.3%O2/8.1%CH4/75.6% N2/Al) were experimentally measured at different concentrations of aluminum suspensions with the aluminum particles having an average size of about d32=5.6μm. Experiments were performed with freely propagating flames in a 48-mm-inner-diameter Pyrex glass tube. A set of parallel equidistant metal plates was installed at about 50cm from the open tube end, forming parallel channels. The flame was initiated at the upper open tube end and propagated downwards. Benchmark experiments performed with an inert silicon carbide (SiC) powder suspension in the same gaseous mixture have demonstrated a steady increase of the quenching distance from about 3.5mm for an unseeded methane flame to about 9.5mm for a flame seeded with 270g/m3 of SiC. At higher SiC concentrations, the flame failed to propagate down the tube. Coupled aluminum–methane flame fronts only appeared above a threshold aluminum concentration around 300g/m3. Below this concentration, the appearance and quenching behaviors of the methane flame seeded with reactive aluminum and inert SiC dusts were similar. The coupled aluminum–methane flame demonstrated two quenching modes. At concentrations below 400g/m3, the aluminum flame decoupled from the methane flame and quenched while the methane flame still propagated. The quenching of a decoupled methane flame in a narrow channel resembles the quenching behavior of the inert powder-seeded flame. At concentrations above 400g/m3, only a coupled aluminum–methane flame could be observed to propagate, or be extinguished, as a whole and exhibited a weaker dependence of the quenching distance on aluminum concentration. These results were interpreted in terms of models for binary fuel mixtures wherein the second fuel to react is completely decoupled, separated by a fixed distance, or merged with the initial flame front.