Aluminum Research Articles

Secondary phase increases the elastic modulus of a cast aluminum-cerium alloy

Alloying in metal castings is one of the principal methods of strengthening an alloy for various structural and functional applications, but very rarely does it modify an alloy’s elastic modulus. We report a methodology of combining isostructural Laves phases to form a multi-component, high symmetry, isotropic phase that was discovered to enhance the elastic modulus of a cast aluminum alloy to 91.5 ± 7.4 GPa. Flux grown single crystals of the rhombicuboctahedron phase (RCO), so named for the observed morphology, were used to enhance understanding of the structure and mechanical properties of the phase. The pure RCO phase’s structure and site occupancies were co-refined using x-ray and neutron diffraction. Dynamic nanomechanical testing of the cast alloy shows the primary RCO phase has a high, relatively isotropic, elastic modulus. This RCO containing aluminum alloy is found to have a specific modulus that exceeds that of the leading Al, Mg, Steel, and Ti alloys.

Achieving significant grain refinement efficiency in Mg-Al alloys via a GNP@MgO composite refiner

Master alloys containing Zirconium (Zr) serve as effective grain refiners in most commercial cast magnesium (Mg) alloys. However, their efficacy is diminished in Mg–Al series alloys due to the formation of Al–Zr compounds. In this work, a novel Mg-GNP@MgO master alloy was prepared utilizing the in-situ reaction between CO2 and Mg. The grain refinement efficiency of this composite inoculation on Mg–9Al alloys was systematically investigated using SEM-EBSD, HRTEM observations, Density Functional Theory (DFT), and Sharp Interface Model (SIM) calculations. The findings suggest that the composite grain refiner (GNP@MgO) exerted a notable refining influence on Mg–9Al alloy. Through the conventional casting process, the average grain size was refined to approximately 13 μm upon the addition of 3 vol% GNP@MgO, achieving a grain refinement efficiency of 90 %. The enhanced refining efficiency arises from the synergistic control over the nucleation and growth processes of α-Mg grains, facilitated by GNP@MgO particles. This process includes improved heterogeneous nucleation, triggered by the newly formed Al4C3 phases through the interaction between GNPs and Al element, followed by the limited expansion of α-Mg grains induced by the nano-sized MgO particles. The MgO particles predominantly gather around grain boundaries to establish stable nano-coating layers, thereby exerting a substantial Zener pinning effect. The pinning role played by the MgO nanoparticles was also verified by a sharp interface model. The findings in this work not only carve out a new avenue for the grain refinement of cast Mg–Al alloys but also inspire fresh perspectives for the development of novel grain refiners.

The effect of chemical short-range order on incipient plastic behavior in FCC structured high entropy alloys

Chemical short-range order (CSRO) was assumed as one of the most important structure feature of high entropy alloys and the influence of CSRO on mechanical properties is a fundamental issue yet to be fully understood. In this work, we performed extensively nanoindentation experiments on CoCrFeNiAlx alloys to study the effect of CSRO on the incipient nanomechanical properties. The statistical nature of strengths at the first pop-in event was analyzed to gain insight of deformation mechanisms. All samples examined here exhibit bimodal distribution which indicate non-unique dislocation nucleation mechanisms. The bimodal distributions can be decomposed into two Gaussian distributions and the activation volumes can be obtained in the range of 0.73–1.38b3. The peaks shift to higher stress level after the development of CSRO. The heterogeneous dislocation nucleation plays a dominant role at low indentation stress with the aid of pre-existing crystalline defects. The homogeneous dislocation nucleation mechanism prevails when indentation stress close to theoretical values. The transmission electron microscopy characterization indicates the presence of chemical ordering in the aged samples. Both the degree of chemical ordering and lattice distortion are much higher in the Al containing HEAs due to the distinctive difference of properties in Al and other transition element atoms.

Microstructure characteristics for improved thermal shock reliability of sintered Ag[sbnd]Al paste in SiC power module

To meet the harsh thermal shock (−50–250 °C) requirements of power device packaging, a novel sintered Ag-based die attach material based on the sustained release effect of Al was proposed. In this study, Al particles with natural core-shell structure covered with Al2O3 layer were selected as the ideal doping-phase, and micron Al particles doped sintered Ag composite paste (AgAl) was prepared. First, the microstructural evolution of sintered AgAl joints during thermal shock was studied. The results showed that Al particles effectively suppressed the cracks generation, which attributed to the sustained release effect of Al element. To clarify sustained release mechanism of Al, the interfaces evolution between Ag and Al particles was investigated. In the initial stage, Al was covered by the Al2O3 layer, preventing inter-diffusion between Ag and Al. As the thermal shock proceeds, the Al2O3 film was fractured, achieving direct contact between metal Al and Ag. Diffusion thus takes place. For the sintered Ag5Al joint, the shear strength was 17.3 MPa after 1000 cycles, which is 1.57 times that of pure sintered Ag joint. These results indicate the successful development of low-cost, high-reliability die attachment materials for use in harsh thermal shock environments.

Laser Non-Destructive Test to Find Aluminum Metal Physical Properties

Laser Non-Destructive Test to Find Aluminum Metal Physical Properties

A New Structural Motif in Aggregation of Methylalumoxanes: Non-Hydrolytic Route by the Alkylation of Dicarboxylic Acids.

Alumoxanes are typically produced via controlled hydrolysis of short-chain alkyl aluminium compounds which leads to oligomeric species that are usually difficult to obtain in crystalline form. Simultaneously, various alternative non-hydrolytic approaches to alumoxanes have also been used. In this work, we report on a new methylalumoxane scaffold derived from the alkylation of a series of dicarboxylic acids: itaconic acid (HO2CCH2C(=CH2)CO2H), succinic acid (HO2CCH2CH2CO2H) and homophthalic acid (HO2CCH2C6H4CO2H). The reactions of AlMe3 with a selected dicarboxylic acid in the molar ratio 4 : 1 conducted at elevated temperature occur with double methylation of each carboxylic group and provide to the formation of a new methylalumoxane aggregate, Me10Al6O4, flanked by methylaluminium diolate units. We also aimed to obtain dialkylaluminium derivatives of dicarboxylic acids by the controlled reaction of the appropriate acid with AlMe3 in the 1 : 2 stoichiometry. While the synthesis of organoaluminium derivatives of flexible aliphatic dicarboxylic acids (itaconic and succinic acids) is challenging due to their insolubility, the related homophtalate compound readily forms a molecular tetranuclear cluster, [([(O2CCH2C6H4CO2)(μ-AlMe2)2]2. The molecular and crystal structures of the resulting compounds were determined via NMR spectroscopic analysis and single crystal X-ray diffraction crystallography.

Regulating the photoluminescence of aluminium complexes from non-luminescence to room-temperature phosphorescence by tuning the metal substituents

Although luminescent aluminum compounds have been utilized for emitting and electron transporting layers in organic light-emitting diodes, most of them often exhibit not phosphorescence but fluorescence with lower photoluminescent quantum yields in the aggregated state than those in the amorphous state due to concentration quenching. Here we show the synthesis and optical properties of β-diketiminate aluminum complexes, such as crystallization-induced emission (CIE) and room-temperature phosphorescence (RTP), and the substituent effects of the central element. The dihaloaluminum complexes were found to exhibit the CIE property, especially RTP from the diiodo complex, while the dialkyl ones showed almost no emission in both solution and solid states. Theoretical calculations suggested that undesired structural relaxation in the singlet excited state of dialkyl complexes should be suppressed by introducing electronegative halogens instead of alkyl groups. Our findings could provide a molecular design not only for obtaining luminescent complexes but also for achieving triplet-harvesting materials.

Highly Efficient Carbonylation of Propylene Oxide into β‐Butyrolactone Catalyzed over Co‐Al Bimetallic Species†

AbstractRational designation of the catalyst for efficient atom‐economic conversion of propylene oxide (PO) and carbon monoxide (CO) into β‐butyrolactone is of current significance. By employing the O,N,O‐tridentate ligands R1,R2LH2 (1–4), the aluminium compounds (R1,R2LAlCl)2 (R1,R2=H,H (5), tBu,tBu (6), Cl,Cl (7), Br,Br (8)) and the derived anion‐cation pairs [H,HLAl(THF)3]+[Co(CO)4]− (9) and [(R1,R2LAl)2Cl(THF)2]+[Co(CO)4]− (R1,R2=tBu,tBu (10), Cl,Cl (11), Br,Br (12)) as well as the aluminium‐cobalt bimetallic cluster compounds [(R1,R2LAl)2Cl(THF)][Co3(CO)10] (R1,R2=tBu,tBu (13), Cl,Cl (14), Br,Br (15)) were prepared. Compounds 9–12 efficiently catalyzed the PO carbonylation into β‐butyrolactone to achieve up 93.4–98.9 % yields while 13–15 gained 95.2–99.0 % yields all at 25 °C and 0.1 MPa CO pressure. The Lewis acidic property of the aluminium compounds 5–8 was investigated. The kinetic of the catalytic reaction using compound 10 was studied. The cooperatively catalytic reaction mechanism by the Co−Al bimetallic species is proposed.

Study on the microstructure, mechanical and corrosion behaviors of 2A12 Al matrix composites containing B4C and 50% K2TiF6 flux

This study presents an innovative exploration into the development and characterization of boron carbide (B4C) reinforced aluminum (Al) metal matrix composites (AMMCs), specifically focusing on the 2A12 Al alloy. Utilizing a cutting-edge vacuum induction melting process, the research investigates the effects of varying B4C particle concentrations in conjunction with 50% K2TiF6 flux additions. This novel approach aims to enhance the microstructural integrity, mechanical properties, and corrosion resistance of the AMMCs. The research unveils a significant improvement in microhardness and tensile strength with the increase of B4C content. This enhancement is attributed to the efficient load transfer mechanism from the aluminum matrix to the B4C phase and the thermal expansion coefficient mismatch-induced dislocations. A critical finding of this study is the uniform distribution of B4C particles and the formation of a Ti-rich layer around these particles, facilitated by the K2TiF6 flux. This layer acts as a barrier, minimizing interfacial reactions. Electrochemical testing reveals that there is a slight decrease in corrosion resistance with increased B4C content. The outcomes of this research contribute to the field of metal matrix composites, offering a path forward for the application of B4C-reinforced AMMCs in demanding industrial environments where high strength, stiffness, and durability are critical. The study's findings open new avenues for advanced materials development in aerospace, automotive, and energy sectors.

The rare-earth elements recovered from the leachate of discarded phosphor by electrodeposition

ABSTRACT Recovering rare-earth elements (REEs) from discarded phosphors is an important solution to alleviate the current shortage of rare-earth resources, the aluminum element in discarded phosphors will badly affect the purity and recovery of rare-earth elements. An electrodeposition method for recovering the rare earth from the discarded phosphoric leachate was proposed to avoid the effecting of aluminum elements. The results show that the purity of the rare-earth oxides recovered reached 99.13% and the recovery rate of rare-earth elements reached 98.89% by adopting the optimal electrodeposition process with the help of the complexing agent glycine. Research has found that adding the complexing agent glycine can help rare-earth hydroxides precipitate at the cathode and inhibit aluminum ion precipitation by changing the aluminum deposition potential. Moreover, it was also found that the generation of OH- ions by reduction of NO3- in acid aqueous solution was a one-step irreversible reaction in the deposition process by cyclic voltammetry, which ensured the reliability of rare-earth hydroxide precipitation reaction.

The aging-hardening behavior of short-time in high pressure die casting AlSi9MgMnZn alloy

Short-time aging is an effective industrial technique for enhancing the mechanical properties of high pressure die cast (HPDC) aluminum alloy components. However, the evolution of precipitation behavior during short-time aging of HPDC alloys remains unclear. In this study, the short-time aging behavior of HPDC AlSi9MgMnZn alloy was investigated. The results show that the AlSi9MgMnZn alloy exhibits effective aging-hardening, with an increment in hardness of approximately 30 HV through the optimal short-time aging treatment (aged at 180 °C for 120 minutes). Higher aging temperatures led to reduced peak hardness and rapid over-aging above 220 °C. The microstructure observation indicates that the peak short-time aging promotes the simultaneous precipitation of β″ precipitates, GP zones and nano Si phases. The contribution of different strengthening mechanisms to hardness was estimated, implying that the coexistence of β″ precipitates and GP zones can provide a positive contribution to aging-hardening during short-time aging. Moreover, as the aging temperature increases, the appearance of β′ precipitates reduces the strengthening effect, leading to a decrease in hardness.

Ultrafast joule-heating synthesis of FeCoMnCuAl high-entropy-alloy nanoparticles as efficient OER electrocatalysts

High entropy alloys (HEAs), known for their synergistic orbital interactions among multiple elements, have been recognized as promising electrocatalysts for enhancing the sluggish kinetics of oxygen evolution reaction (OER). Despite their potential, the facile and rapid preparation of HEA nanoparticles (NPs) with high electrocatalytic activity remains challenging. Here, we report an ultrafast synthesis of noble-metal-free FeCoMnCuAl HEA NPs loaded on conductive carbon fiber networks using a Joule heating strategy. The prepared HEA NPs exhibited a face-centered cubic (FCC) structure with an average size of approximately 25 ​nm. Synchrotron X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS) studies were performed to investigate the atomic and electronic structures of the HEA NPs, revealing the co-presence of Fe, Co, Mn, Cu and Al elements as well as their different valences across surface and internal regions. The HEA NPs showed remarkable OER performance, exhibiting an overpotential of 280 ​mV at 10 ​mA ​cm−2 and a low Tafel slope of 76.13 ​mV dec−1 in a 1.0 ​M KOH solution with high electrochemical stability, superior to commercial RuO2 electrocatalysts. This work provides a new approach for synthesizing nanoscale noble-metal-free HEA electrocatalysts for clean energy conversion applications on a large-scale basis for practical commercialization.

Separation of Used Coolants From High-Pressure Aluminium Alloys Die-Casting Via Turbidimetric Method

Abstract The growth of the automotive industry and increased efforts to reduce the environmental impact of transportation require the use of more and more aluminium components in the production of new cars. The process of high-pressure die casting of aluminium makes it possible to meet the goals, but it requires the use of coolants based on oil and wax emulsions that are difficult to dispose of. A method for demulsification of real wastewater samples from the high pressure die casting process was developed and evaluated. The optimal parameters for conducting the separation process were determined, and the changes occurring in the emulsion being separated were analysed.

Microstructure evolution of a novel low-silicon cast aluminum alloy modified with Mn and Cr during solution treatment

The evolution of eutectic Si, the precipitation behavior of dispersoids and microhardness change of the α-Al matrix in a Mn + Cr modified Al-Si-Mg-Cu alloy during solution treatment were investigated. The results revealed that the evolution of eutectic Si was divided into four paths during solution treatment: Dissolution, splitting, spheroidization and coarsening. Meanwhile, numerous α-Al(FeMnCr)Si dispersoids were precipitated in the eutectic region and the α-Al dendrite arms after solution treatment for 30 min. Due to differences in precipitation behavior, three different dispersoid precipitation zones were formed in the dendrite arms, including the dispersoid-free zone (DFZ) near the grain boundaries, coarse dispersoid zones (CDZ) located in the dendrite cores, and the remaining fine dispersoid zones (FDZ). The bimodal size distribution of the dispersoids within intradendritic regions were closely related to the micro-segregation of Mn and Cr. The precipitation of coarse grain boundary phases exhausted the Fe solute near the grain boundary, which was mainly responsible for the formation of the DFZ. Moreover, there was a partial coherent interface between the dispersoids and the α-Al matrix. The evolution mechanism of matrix microhardness can be well explained by dispersion strengthening effect

Fabrication and Characteristics of Cast Aluminium – Mineral Particles Composite

Fabrication and Characteristics of Cast Aluminium – Mineral Particles Composite

Impregnation problems of aluminum castings

Abstract Vacuum impregnation is an effective solution to the porosity problem of aluminum die castings. Experience has shown that quality die-cast aluminum alloy products manufactured with gas tightness requirements can show leakage even after impregnation operation. The study seeks to answer the question of the geometry of the cavity system through which leakage occurs and why the cavity system is not saturated with liquid resin during impregnation. It is assumed that insufficient impregnation occurs if the near-surface parts of the cavity system are heavily deformed locally during the machining of the casting.

Thermodynamic evaluation of metal foams with partial filling in a pipe

This study presents numerical findings on the flow and heat transfer irreversibility when metal foams are partially filled in a horizontal pipe. A heater is embedded in the pipe's circumference with a known heat input. Aluminum metal foam, characterized by a pore density of 10 and porosity of 0.95, is placed next to the inner wall of the pipe to enhance heat transfer. To determine the optimal thickness of the metal foam for thermodynamic performance enhancement, metal foams of five different thicknesses (10–80 mm) are examined under forced convection heat transfer conditions. The study integrates the Darcy Extended Forchheimer and local thermal nonequilibrium models to predict flow and heat transfer characteristics through the metal foams. Validation of the numerical methodology is conducted by comparing the results with experimental data available in the literature. A novel aspect of this investigation is the application of the second law of thermodynamics to analyze the thermodynamic performance of metal foams. Exergy and irreversibility analyses are used to evaluate the thermodynamic performance, revealing that a pipe filled with metal foams up to a thickness of 40 mm exhibits superior thermodynamic performance compared to other cases examined in the study.

Mechanical Performance and Corrosion Behaviour of Aluminum7075 Reinforced by Nano-Titanium dioxide

في هذه الدراسة ، تم تطبيق تقنية الصب بالتحريك (SCT) لتكوين مركب الألمنيوم (Al) النانوي مع نسب وزنية مختلفة من مسحوق ثاني أكسيد التيتانيوم النانوي (TiO2). تم فحص الخصائص البنائية ,الميكانيكية والتآكل لمتراكبات النانو. دراسة البنية المجهرية تمت عن طريق المجهر الإلكتروني الماسح (SEM) ، بينما تم الحصول على التركيب البلوري للعينات باستخدام حيود الأشعة السينية (XRD). بالإضافة إلى ذلك ، تم غمر المركبات النانوية في محلول 0.5 مولاري من حمض الهيدروكلوريك لقياسات معدل التآكل والديناميكية الفعالة. أظهرت النتائج أن أفضل عينة كانت 0.03٪ ، حيث زادت الصلابة بنسبة 23٪ ، لكن قوة الشد زادت إلى 52٪. حيث أظهرت صور SEM للعينات المعززة بالجسيمات النانوية تجانسًا وانتشارًا واضحًا للجسيمات النانوية في المصفوفة. لذلك ، فإن إضافة جزيئات TiO2 النانوية إلى معدن الألمنيوم أدى إلى تحسين صلابة وقوة الشد للمركبات النانوية بشكل ملحوظ. بالمقابل أظهرت نتائج التآكل أن المواد المركبة النانوية لديها مقاومة تآكل أعلى من المواد المركبة القائمة على Al7075.

Investigation of wear characteristics of granite dust & coconut shell ash reinforced aluminum metal matrix composite using design of experiment

Recently, one of the most important issue faced by all nations is a waste management. Therefore, it is essential to search for creative solutions to waste reduction, reuse, and recycling. This can be accomplished by adding waste materials to composite materials as a reinforcements. Reusing waste materials enhances the characteristics of existing materials, while also helping the environment by solving the disposal problem. The main aim of this paper is to study the wear characteristics of hybrid aluminum metal matrix composite reinforced with coconut shell ash (CSA) and granite dust. The hybrid composite samples were manufactured using stir casting by reinforcing CSA (ranging from 0 wt% to 12 wt%) and granite dust (maintained at 2 wt%) in Al6061 alloy. SEM and EDAX analysis were performed to investigate the microstructure and elemental composition. The wear characteristics of the hybrid composites were determined via pin-on-disc tests. Finally, the Taguchi design of experiment was performed on the specimen having the best wear characteristics by selecting the L27 orthogonal array and identified the influence of process variables on the wear rate. The results of the pin-on-disc experiment showed that the wear rate decreased with increasing CSA%. The hybrid composite composed of 02 wt% granite dust, & 12 wt% CSA indicates a lower wear rate (56.25%) as compared to the matrix alloy. The Taguchi analysis prooved that the sliding distance has a greater impact on the wear rate than the other parameters. This material can be a superior substitute where high wear resistance is required.

P23-15 Pulmonary toxicity is the most sensitive endpoint for deriving MAK values for aluminium compounds

P23-15 Pulmonary toxicity is the most sensitive endpoint for deriving MAK values for aluminium compounds