Complex Aluminum Research Articles

Nanotechnology enabled casting of aluminum alloy 7075 turbines

Aluminum alloy 7075 is well-known for its high-performance structural systems due to its lightweight and excellent mechanical properties. However, its susceptibility to hot cracking and limited fluidity hinder its casting suitability, posing challenges in manufacturing near-net-shaped structures economically, especially for thin and intricate aerospace components. This paper presents experimental results based on nano-treating, an emerging nanotechnology-enabled manufacturing method by incorporating a low fraction of nanoparticles in liquid aluminum, to allow the casting of complex aluminum alloy 7075 parts. Vacuum fluidity tests demonstrated that nano-treating of aluminum alloy 7075 with only 0.5 vol% TiC nanoparticles increased the fluidity of aluminum alloy 7075 by more than 20%, effectively eliminating hot cracking and enhancing surface quality. Through the Rapid Investment Casting process, nano-treated aluminum alloy 7075 can be successfully cast into turbines with 0.5 mm thick blades. In contrast, aluminum alloy 7075 without nano-treating failed to produce good casting quality due to poor filling and severe cracks. The manufacturing trials highlight the significant improvement in castability achieved through nano-treating, opening a novel pathway for the cost-effective production of complex aluminum alloy 7075 structures for numerous applications.

Uneven distribution of cooling rate, microstructure and mechanical properties for A356-T6 wheels fabricated by low pressure die casting

Complex aluminum alloy part prepared by low pressure die casting (LPDC) usually has unevenly distributed microstructure and mechanical properties, which is related to the cooling conditions. To investigate the uneven characteristics of cooling rate, microstructure and mechanical properties of LPDC-fabricated A356-T6 wheels, the typical positions (including hub, spoke, outer flange, rim and inner flange) were selected to calculate the cooling rate by casting simulation. Then, the microstructure, mechanical properties, X-ray result and element content of these positions were analyzed in detail. The result shows that, the secondary dendrite arms spacing (SDAS), eutectic silicon and β-Fe phase have the largest size at hub, and the eutectic silicon is plate-shaped when the cooling rate is 10 K/min, which results in poor ultimate tensile strength (UTS, 192 MPa) and elongation (2.1 %). While at the cooling rate of 100 K/min, refined microstructure, the disappearance of β-Fe phases and the elimination of defects result in good mechanical properties of the outer flange. The UTS and elongation exceed 250 MPa and 13 %, respectively. The rim is more prone to occur shrinkage defects at high cooling rate, which results in mechanical properties that do not meet expectations. Furthermore, the Si, Mg, and Fe elements also exhibit uneven distribution in different positions of LPDC-fabricated A356-T6 wheels. The maximum deviation of Si element between the actual content and the standard content is as high as 21 %.

Deburring of Soft, Complex Aluminium Alloy Parts

This Processs investigates the effectiveness of utilizing a vertical drill machine to integrate a brush for deburring soft aluminum parts. The aim is to enhance the efficiency and precision of the deburring process in manufacturing operations. The project involves the design and assembly of a specialized attachment to the drill machine, enabling seamless integration of the brush. Through experimental analysis, the performance of the integrated system is evaluated in terms of deburring quality, time efficiency, and cost-effectiveness compared to traditional deburring methods. The results demonstrate significant improvements in deburring effectiveness and productivity, highlighting the potential of this approach for enhancing manufacturing processes involving soft aluminum parts. This technique is so affordable price.

Changes in Microstructure and Texture of a Multi-Stack Accumulative Roll Bonding Processed Complex Aluminum Alloy with Annealing

Changes in Microstructure and Texture of a Multi-Stack Accumulative Roll Bonding Processed Complex Aluminum Alloy with Annealing

A novel superhydrophobic Al conductor with excellent anti-icing performance and its mechanism

Overhead conductor icing is one of the main factors causing transmission line failures. Superhydrophobic surface (SHS) with composite pore structure exhibits excellent anti-icing effectiveness and durability. Herein, this novel SHS was prepared on complex aluminum conductors by two-step anodic oxidation technology, and the motion behavior of droplets on the SHS conductor in the glaze icing environment was studied experimentally to analyze the anti-icing mechanism. The simulated glaze icing experiment results show that the SHS conductor significantly reduces the ice accumulation, and the icing weight is only 23 % of the untreated conductor. Compared with the flat surface, the groove structure of the SHS conductor enhances the ability of millimeter-sized droplets to bounce, and the contact time is less than 9 ms. Also, micron-sized spraying droplets exhibit excellent mobility on the SHS conductor surface, and the contact time is further reduced. Moreover, the SHS conductor has a good ability to delay the freezing of spraying droplets. The above factors endow the SHS conductor excellent anti-icing performance. This work lays a foundation for the anti-icing application of SHS on transmission lines.

Nanocontrolled thinning of the barrier layer thickness of porous anodic films using galvanodynamic polarization of aluminum alloys

Thinning the barrier layer thickness of anodic films prepared on refined aluminum substrates (4 N or 5 N) was usually performed to elaborate -after the usual two-step anodizing method- anodic aluminum oxide (AAO) templates with pores opened at both sides, allowing the subsequent nanodevices synthesis. By contrast, there is a lack of studies concerning similar barrier layer thinning for anodic films grown -by a single-step anodizing - on commercial low alloyed aluminum substrates (1XXX series) or other more complex aluminum alloys (AA 2XXX-8XXX). Yet such a need is now emerging, particularly for future applications requiring transverse electrical conductivity of usual anodic films toward the aluminum alloy substrate.This work aims to study and to master a simple and cheap method for thinning the barrier layer thickness of such anodic films on commercial aluminum alloys. Here, the thinning is studied using a current density decrease (at a constant rate) after the anodic film growth in phosphoric acid-based electrolyte, using the conjunction of in-situ accurate electrochemical follow-up and ex-situ FE-SEM morphological observations. Variation of current density scan rate highlights that fast processes lead to no barrier layer thinning, and slow ones to the detachment of the whole oxide film. However, by choosing the right scan rate range, it is possible to successfully obtain, in a straightforward manner, anodic films still supported on aluminum alloy substrates, but with barrier layer thickness tuned at the nanoscale.

Low-Waste Synthesis and Properties of Highly Dispersed NiO·Al2O3 Mixed Oxides Based on the Products of Centrifugal Thermal Activation of Gibbsite

This study revealed an increased reactivity of centrifugally thermoactivated products of gibbsite toward aqueous solutions of nickel nitrate at room temperature as well as under hydrothermal conditions. X-ray, thermal, microscopy, adsorption and chemical analysis methods were used to investigate and demonstrate the possibility of obtaining highly loaded mixed aluminum–nickel oxide systems, with a nickel content of ca. 33 wt.%, using a hydrochemical treatment at room temperature or a hydrothermal treatment of suspensions of the product of the centrifugal thermal activation of gibbsite in aqueous solutions of nickel nitrate. It was shown that the thermal treatment of xerogels—hydrochemical interaction products—in the range of 350–850 °C led to the formation of NiO phases and highly dispersed solid solutions of nickel based on the NiAl2O4 spinel structure, with different ratios and a high specific surface area of 140–200 m2/g. A hydrochemical treatment of suspensions at room temperature ensures that the predominant formation of the NiO phase is distributed over the surface of the alumina matrix after calcination, whereas hydrothermal treatment at 150 °C leads to a deeper interaction of the suspension components at the treatment step, which occurs after the thermal treatment of the formed xerogel in the predominant formation of poorly crystallized NiAl2O4 spinel (“protospinel”). The considered method makes it possible to obtain complex aluminum–nickel oxide systems with different phase ratios, decreases the number of initial reagents and synthesis steps, completely excludes waste and diminishes the total amount of nitrates by 75 wt.% compared to the classical nitrate scheme for the coprecipitation of compounds with a similar elemental composition.

Surface modification of typical calcium-containing minerals by aluminum ion and its effect on adsorption of citric acid

In this study, aluminum ion surface modification was used to improve the depressive performance of citric acid on calcite. The micro-flotation experiment showed that the mixed depressant of aluminum ion and citric acid displayed a higher separation effect on the two minerals than the single citric acid, the recovery of scheelite was 90.6 %, but that of calcite was 4.3 % using the mixed depressant. The artificial mixed mineral experiment confirmed that the mixed depressant exhibited an efficient separation effect, and an excellent scheelite enrichment index with WO3 grade of 67.36 % and scheelite recovery of 83.95 % was obtained using 1.0 × 10−4 mol/L aluminum ion and 1.0 × 10−4 mol/L citric acid. The surface characterization methods indicated that the aluminum ion complex was selectively adsorbed on the CO32- sites of the calcite surface in the form of aluminum citrate and monohydrogen aluminum citrate radical. The calculation result of thermodynamic and conditional stability constants revealed that the aluminum species complex aluminum citrate was more easily formed and more stable than monohydrogen aluminum citrate radical. Atomic force microscopy images showed that aluminum ion complexes were selectively adsorbed on the calcite surface in the form of clusters and sheets with higher adsorption height and density than scheelite. This study provides an excellent reagent system using for enriching scheelite.

On the Use of Solomon Echoes in 27 Al NMR Studies of Complex Aluminium Hydrides.

The quadrupole coupling constant CQ and the asymmetry parameter η have been determined for two complex aluminium hydrides from 27 Al NMR spectra recorded for stationary samples by using the Solomon echo sequence. The thus obtained data for KAlH4 (CQ =(1.30±0.02) MHz, η=(0.64±0.02)) and NaAlH4 (CQ =(3.11±0.02) MHz, η<0.01) agree very well with data previously determined from MAS NMR spectra. The accuracy with which these parameters can be determined from static spectra turned out to be at least as good as via the MAS approach. The experimentally determined parameters (δiso , CQ and η) are compared with those obtained from DFT-GIPAW (density functional theory - gauge-including projected augmented wave) calculations. Except for the quadrupole coupling constant for KAlH4 , which is overestimated in the GIPAW calculations by about 30 %, the agreement is excellent. Advantages of the application of the Solomon echo sequence for the measurement of less stable materials or for in situ studies are discussed.

Dehydrogenation of Alkali Metal Aluminum Hydrides MAlH4 (M = Li, Na, K, and Cs): Insight from First-Principles Calculations

Complex aluminum hydrides with high hydrogen capacity are among the most promising solid-state hydrogen storage materials. The present study determines the thermal stability, hydrogen dissociation energy, and electronic structures of alkali metal aluminum hydrides, MAlH4 (M = Li, Na, K, and Cs), using first-principles density functional theory calculations in an attempt to gain insight into the dehydrogenation mechanism of these hydrides. The results show that the hydrogen dissociation energy (Ed-H2) of MAlH4 (M = Li, Na, K, and Cs) correlates with the Pauling electronegativity of cation M (χP); that is, the Ed-H2 (average value) decreases, i.e., 1.211 eV (LiAlH4) &lt; 1.281 eV (NaAlH4) &lt; 1.291 eV (KAlH4) &lt; 1.361 eV (CsAlH4), with the increasing χP value, i.e., 0.98 (Li) &gt; 0.93 (Na) &gt; 0.82 (K) &gt; 0.79 (Cs). The main reason for this finding is that alkali alanate MAlH4 at higher cation electronegativity is thermally less stable and held by weaker Al-H covalent and H-H ionic interactions. Our work contributes to the design of alkali metal aluminum hydrides with a favorable dehydrogenation, which is useful for on-board hydrogen storage.

Electronic structure and stability of a pure sodium alanate clusters Na12Al12H48, and the interstitial space-doped with Ti, C and H atoms, as a promising hydrogen storage system: Density functional theory

Sodium alanate is a complex aluminium hydrogen, which has recently attracted more attention because it can be used as an effective hydrogen storage material. Our goal is to investigate the electronic structure and stability characteristics of promising hydrogen storage materials, including sodium alanate, Na12Al12H48 (12 units of NaAlH4), and which doped (interstitial defects) with Ti, C, and H atoms. The B3lyp/Sto-3G density functional theory based on quantum mechanical calculations uses DFT to obtain crucial information on chemical stability and reactions, such as possible structures (optimal bond length), electronegativity (ω), hardness (η), softness (S), ionization potential (IP), electron affinity (EA), energy gap (Eg), electronic chemical potential (μ), Fermi energy level (EF), maximum charge transfer (ΔN max), work function (ɸ), and electrophilicity (χ). These DFT-based global reactivity descriptors are sufficient to provide a better understanding of chemical systems in terms of their stability and reactivity. The interstitial doping by these atom positions places all binding lengths without any other significant change from the Na12Al12H48 crystal structure. Na12Al12H48 sodium lanate is slightly distorted. Na12Al12H48–H is very reactive and stability is low. The Na12Al12H48 –H cluster is expected to be promising in the formation of new compounds. On the other hand, the higher band gap values found for pure Na12Al12H48 clusters correspond to greater stability. Analysis of the length of the bonds and electronic properties shows that the sodium alanate grid was relatively uninfluenced by the interstitial space enriched with Ti, C, and H atoms. These results also show that the role of the C, Ti, and H atoms added to sodium alanates is not a “interstitial space doping” element but a catalyst.

Deformation characteristics and inertial effect of complex aluminum alloy sheet part under impact hydroforming: experiments and numerical analysis

Impact hydroforming (IHF), as a novel sheet metal forming technology with the advantages of high strain rate forming and flexible liquid loading, is highly suitable for efficiently manufacturing aluminum complex-shaped sheet parts. In this paper, deformation characteristics of complex sheet parts under IHF are systematically investigated. The mechanical properties of 2024 aluminum alloy under a wide range of strain rates (10−3 s−1–3.3×103 s−1) were studied. It indicated that the elongation of 2024 aluminum alloy was improved by 116.01% under strain rates of 3.306 × 103 s−1, referring to 10−3 s−1. Further, a complex-shaped part with symmetrical and asymmetrical structures was selected. The deformation characteristics of sheet and role of inertial effect under IHF were investigated with well-developed solid–liquid coupling finite element (SLC-FE) model with high accuracy. Differentiating deformation tendency is found for symmetrical structure with notably prior deformation at central zone, showing a “bulging” profile at initial forming stage. Whereas, synchronous deformation is presented for asymmetrical structure with a “flat” profile. Additionally, distinctive inertial effect was observed at different positions change for both symmetrical and asymmetrical structures, in which lower values were resulted at their central regions. Meanwhile, the inertial effect evolved with the impacting speed. Specially, larger difference of inertial effect was observed with increasing impacting speed.

Uniaxial compressive performance of an aramid and aluminum honeycomb sandwich structure

In recent years, explosion and impact resistance capacity of composite sandwich structures has been widely studied. However, the study of their basic mechanical properties is still lacking, which severely hinders the application of composite sandwich structures. This paper focuses on uniaxial compressive performance of a sandwich structure, so as to provide design guidance and promote application of such structures. Firstly, a novel aramid and aluminum honeycomb sandwich structure is proposed for explosion and impact resistance. Secondly, experimental and numerical studies on uniaxial compressive performance of the structure were conducted. Seven indices including yield compressive load were introduced to assess compressive behavior of the structure. A simulation framework to predict load-carrying capacity of the structure is proposed, in which the complex aluminum honeycomb was modeled as a cube with equivalent material properties. The mechanism of how the structure collapses under uniaxial compressive load was revealed. Thirdly, parametric sensitivity analysis was conducted. According to experimental and calculated results, the structure approximately undergoes five stages under progressive compression: uniform shrinkage in vertical direction, yielding at local regions of the weaker panel (rear panel), plastic deformation development on the rear panel, overall bending of the whole specimen, and fracture of localized welds. Front panel thickness and initial imperfection have little influence on compressive behavior of the structure, while thickness of the weaker panel (rear panel) is the decisive factor of compressive load-carrying capacity. Yield load, yield displacement, ultimate load, and elastic stiffness increase linearly with the increase of rear panel (316L) thickness, while ductility coefficient decreases linearly with the increase of rear panel (316L) thickness.

Monometallic motor-axial bearings of diesel locomotives: replacing bronze with complex aluminium alloy

Introduction. Replacing the material of monometallic motor-axial bearings currently manufactured from bronze to aluminium alloy is advisable to improve traffic safety due to the higher reliability and efficiency of such bearings.Materials and methods. This article studies the materials of monometallic motor-axial bearings, bronze and the proposed complex aluminium-tin alloys. Mechanical properties are determined by standard methods: tensile strength, relative elongation (ductility), Brinell hardness, impact strength. Antifriction properties (abradability, score resistance, wear resistance of the antifriction alloy and the steel associated with it, the heating temperature of the steel surface and the coefficient of friction) were determined according to the methods of the Railway Research Institute approved by JSC Russian Railways on the SMTs-2 friction machine. Bronze and three grades of aluminium alloys were tested with M-14V2 diesel oil, and bronze, B16 babbitt and one grade of aluminium alloy were tested with axial oil.Results. This research shows the possibility of replacing bronze with complex-alloyed aluminium alloys both in terms of economic indicators and antifriction properties. A comparison of mechanical properties is carried out, in most of which aluminium alloys are found superior or not inferior to bronze. The exception is ductility, in terms of which bronze surpasses the proposed alloys.Discussion and conclusion. According to the complex of service characteristics obtained in laboratory studies, it seems expedient to replace bronze with complex aluminium antifriction alloy. The final decision on such a replacement could be made after bench and operational tests of motor-axial bearings on diesel locomotives.

A Contemporary Review on Friction Stir Welding of Circular Pipe Joints and the Influence of Fixtures on This Process

The permanent metal joining processes play a vital role in assembling the complex aluminium structures of the aerospace, automotive, marine, and oil industries. The invention of friction stir welding (FSW) redefined the mechanism of metal joining to produce high-quality welds by eliminating the consumption of electrodes and shielding gases, resulting in economical processes. Research works still lack to explore the application of FSW in complex geometries. In this view, the present work reports a critical review of various geometries welded by FSW, mainly circular geometries that are majorly used in the oil and gas industries. The various aspects of the FSW of pipes, such as process facilitation, process parameters, tool material selection, and tool design selection are discussed. The paper also presents insights into the parameters responsible for the weld quality, the feasibility of optimization techniques, and the status of various fixture arrangements. The facilitation requisites for FSW of pipes are also provided based on the reviews made. The review concludes by discussing the challenges associated with the FSW of pipes, economic aspects, and future research directions.

Cracking mechanism and its susceptibility to scanning speed during laser power bed fusion processed high-strength 2024Al alloy

Laser powder bed fusion (L-PBF) is a promising technique for fabricating high-performance complex aluminum (Al) alloy components. However, conventional high-strength wrought Al alloys that are processed using L-PBF have limited application owing to their poor cracking resistance. To investigate the cracking mechanism, L-PBF was used to fabricate a 2024Al alloy. The resultant microstructure exhibited severe hot cracking, which occurred at grain boundaries with a high angle in both solidification and liquation cracks. Increasing the scanning speed increased the susceptibility to cracking. The effect of scanning speed on the eutectics content of Al2Cu and Al2CuMg and the residual stress in as-fabricated samples are discussed. Crack elimination at a low scanning speed could be ascribed to the lower thermal stresses and adequate liquid feeding during the late stage of solidification. In addition, based on the RDG (Rappaz-Drezet-Gremaud) model, a cracking susceptibility map was produced, in which the cracking susceptibility was determined to increase with an increase in the solidification rate, in agreement with experimental observation.

Preventing Crack in an Aluminum Alloy Complex Structure during Welding Process Based on Numerical Simulation Technology

Aluminum alloy structures are widely used for weight reduction in aviation, shipbuilding, rail vehicles and automotive industries. Fusion welding technology is one of the most important joining methods for lightweight structure assembly due to its advantages such as flexibility in design, high production efficiency, and low cost. However, the local centralized heating during fusion welding inevitably produces residual stress and welding deformation. For actual engineering structures, if the product design is unreasonable or the external restraint is inappropriate, the transient stress or residual stress become a key factor resulting in cracking during the assembly process. In the current study, an effective computational approach was developed based on the MSC Marc software to simulate transient and residual stress fields for complex aluminum alloy structures during the welding process. In the developed computational approach, according to the location and arrangement of welding lines, an instantaneous heat source model was used to replace the traditional moving heat source model, and as a result significanlty improved the calculation efficiency to meet actual engineering needs. The welding stresses, including transient and residual stress, of an A6061 aluminum alloy complex structure were calculated by the developed numerical simulation technology. The simulation results indicated that the cracking was produced by excessive transient stress during welding process. Subsequently, the effect of external restraint intensity on welding stress at the key location was examined numerically. Based on the simulation results, measures to reduce welding stress and cracking risk were put forward based on adjusting the external restraint intensity.

Straw type and returning amount affects SOC fractions and Fe/Al oxides in a rice-wheat rotation system

Straw returning is a vital agronomic practice for soil organic carbon (SOC) sequestration and stabilization by changing the storage and fraction composition. Iron and aluminum (Fe/Al) oxides have a protective effect on SOC through adsorption and co-precipitation, which depends on the fraction composition of SOC itself, especially originated from externally added organic materials. However, the changes and interactions of SOC components and Fe/Al oxides in straw returning soil are not clearly understood. To evaluate the effect of straw returning on SOC composition and Fe/Al oxides, we have conducted an in situ field experiment for 10 yrs., which including five treatments: no rice and wheat straw returning (NRW, as control), total amount wheat straw returning (W), total amount rice straw returning (R), half amount rice and wheat straw returning (HRW), and total amount rice and wheat straw returning (TRW). The results showed that SOC and heavy fraction organic carbon (HFOC) increased under all five treatments, especially for R, HRW, and TRW treatments (P < 0.05). Compared with wheat straw returning, rice straw returning was more conducive to increasing the contents of SOC and its fractions, free Fe/Al oxides, complex aluminum oxides and the carbon utilization efficiency. Collectively, these properties were strongly affected by both the type and amount of straw returning. Soil organic carbon was significantly correlated with HFOC, water-soluble organic carbon, alkali-hydrolyzed nitrogen, available phosphorous, available potassium, and total nitrogen (P < 0.05). Of these, HFOC had the most significant effect on SOC and was vitally important for improving SOC sequestration and stability (P < 0.001). The increase of labile carbon fractions was more conducive to the absorption and utilization of nutrients by crops. Straw returning promoted the interaction between increasing organic matter and complex iron oxide (Fec). This served to strengthen the protective effect of SOC, which increased the content of Fec and stability of SOC, resulting in decreased soil pH. Taken together, these results highlight the importance of straw returning in promoting the storage and stability of SOC pool. Critically, rice straw returning can reduce soil pH and Fec content, therefore could be considered as an ideal model for a rice-wheat rotation system.

Digital Twin and Data-Driven Quality Prediction of Complex Die-Casting Manufacturing

Digital twin and data-driven technologies provide an idea for realizing complex product quality prediction. Aiming at the issues of real-time visual monitoring, operating status analysis, and quality prediction in complex die-casting intelligent manufacturing, a digital twin and data-driven quality prediction architecture is proposed. The virtual-real interaction digital twin of die-casting manufacturing cells is established. The collaborative working mode of physical cells, virtual cells, and real-time monitoring is constructed to predict product quality. The learning method of die-casting parameter data and appearance defect data is proposed to realize the real-time quality prediction in die-casting process and the appearance defect quality prediction after processing, respectively. The data preprocessing and XGBoost-based learning method is proposed for real-time quality prediction of die-casting process. A single-shot refinement neural network for aluminum casting tiny defects detection (Refine-ACTDD) based on deep learning is proposed to solve the high-precision defect detection problems of small appearance defects of complex castings and large interference of complex background. Taking the complex aluminum die-casting as an example, the applications of quality prediction are verified. The method provides a new technical approach for high-precision quality prediction of complex die-casting manufacturing.

Geometry-based Assurance of Directional Solidification for Complex Topology-optimized Castings using the Medial Axis Transform

Using structural optimization is ideal for the development of complex aluminum cast parts, due to the high degree of design freedom. Various casting processes exist for production, and these differ in their boundary conditions and process restrictions. The resulting geometric restrictions have so far only been taken into account to a limited extent in structural optimization. Hence, there is a desire to determine simple process restrictions that can be taken into account to generate component geometries that are as light as possible but can still be produced by casting. This paper addresses the automated validation and optimization of directional solidification for topology-optimized geometries for castings. For the parametric description of the component volume, the medial axis transform (MAT) method is chosen. This approach allows a subsequent evaluation and optimization by methods of graph theory and feedback into an adapted surface file. The optimization results are finally evaluated by a process simulation using the finite volume method.