Recycled Aluminum Research Articles

Feasibility Study of Solid-State Recycling through Direct Hot Rolling of AA5754 Aluminum Chips for Automotive Applications

Recently, researchers have done a lot of efforts to develop new solid-state recycling processes, both experimentally and developing numerical models. This kind of process is energy-saving and environmentally friendly compared to the conventional aluminum recycling process because avoided the melting step. The purpose of this work is to evaluate the feasibility of an innovative solid-state recycling process through direct hot rolling in a non heat-treatable aluminum alloy for automotive applications. AA5754 chips have been produced by turning a bar without the usage of lubricants and compacted with a 150 kN load; the compacted billets were treated at 400 °C and directly hot rolled in several successive passes. Rolled samples are then analyzed in terms of Vickers microhardness and microstructure in both as-rolled and heat treatment conditions, this last was performed at 185°C simulating the process of paint-bake. The produced samples show an excellent bonding between chips.

Effect of Alumina as Reinforcement on the Mechanical and Physical Properties of Recycled AA6061 Aluminium

The utilisation of reinforcement materials in aluminium metal matrix composites is widely used in the manufacturing sector due to their lightweight nature, excellent strength-to-weight ratio, enhanced fracture toughness, and improved mechanical properties. The purpose of this study is to investigate the effect of reinforcing alumina in recycled AA6061 aluminium on the properties of the resulting aluminium matrix composite. Various compositions of recycled AA6061 aluminium reinforced with alumina were prepared and analysed using the cold compaction method. The results show that the addition of alumina composition increases the hardness properties of the composite by up to 5 wt.% at 32.91 Hv compared to the unreinforced sample at 30.63 Hv, but the hardness decreases as the alumina mass composition increases. According to the analysis of physical properties, in comparison to the unreinforced sample, the density decreases with increasing mass composition of alumina up to 10 wt.%, which is from 2.4636 g/cm3 to 2.3014 g/cm3, respectively. In relation to the microstructure of the samples, the addition of alumina results in irregular shapes with larger pores. An increasing in the mass composition of alumina results in increased porosity and water absorption.

A System Dynamics Supply Chain Analysis for the Sustainability Transition of European Rolled Aluminum Products

This research presents a system dynamics model to study the interaction among demand and supply evolutions, government regulations, sustainable adoption trends, investments in different decarbonization technologies, and environmental requirements for the European Aluminum Rolled Product Supply Chain (ARPSC). It allows stakeholders to assess the quantitative impact of investing in decarbonization technologies on supply chain sustainability. Investing in decarbonization technologies reduces greenhouse gas (GHG) emissions. The most substantial GHG emission reductions can be achieved if upstream ARPSC actors invest according to an aggressive investment strategy between 2031 and 2040. However, even with an aggressive investment strategy, investing in decarbonization technologies alone is likely to be insufficient to achieve the European Green Deal goals. Furthermore, barriers to investment in decarbonization technologies and a low rate of progress in doubling the European Union’s circularity rate may put extra stress on achieving the European Green Deal goals for the European ARPSC. Instead, ARPSC actors will additionally need to optimize the recycling of aluminum rolled products and adopt strategies for resource sufficiency, e.g., by sharing cars and using packaging multiple times.

Tensile and shear behavior of recycled AA 6060 aluminium chips by direct hot extrusion

Solid state recycling of aluminium chips is a promising technique to reduce environmental impacts of secondary production. As the recycling process induces a highly oriented microstructure, this study aims to quantify the mechanical properties of extrudates and identify the role of chip boundaries in the fracture behavior. Tensile and shear tests are performed on heat treated AA 6060 alloy and analyzed using digital image correlation. The tensile behavior of the chip-based material is similar to its cast-based counterpart, reaching a yield strength of 230 MPa. Shear properties are close for small deformations, although the chip-based material have lower ductility due to the early onset of damage at the chip boundary. These results confirm the industrial relevance of this process for large scale recycling of aluminium.

Innovative Recycling and Conversion of Aluminum Waste to Hydrogen and Aluminum Chloride: Enhancing Economic Feasibility and Sustainability in Saudi Arabia

The rapid industrialization and urbanization in Saudi Arabia have led to significant challenges in waste management, particularly in recycling aluminum waste. This study explores an innovative approach for converting aluminum waste, specifically beverage cans, into valuable products such as aluminum chloride (AlCl3) and hydrogen (H2). The process involves the chemical reaction of aluminum with hydrochloric acid (HCl), producing AlCl3 and H2, and is modeled using Aspen Plus software. Two scenarios are evaluated: one without recycling and one incorporating recycling processes. In the first scenario, the direct conversion process yields 355 tons of AlCl3 and 9 tons of H2 per day from 100 metric tons of aluminum waste. The minimum selling price (MSP) of AlCl3 is calculated to be $764 per ton, with an annual profit of $25 million, assuming a market price of $1000 per ton. However, the economic viability of this scenario is highly sensitive to conversion efficiencies and market conditions. The second scenario integrates a recycling loop, processing 90% of the aluminum waste back into aluminum, significantly enhancing economic stability. This scenario produces 35 tons of AlCl3 and 1 ton of H2 per day, with an MSP of $1068 per ton. Despite the higher MSP, the inclusion of recycled aluminum, sold at $2400 per ton, results in a higher annual profit of $38 million, demonstrating greater economic resilience and sustainability. This study provides a comprehensive techno-economic analysis, highlighting the dual benefits of waste reduction and resource recovery. By optimizing reaction conditions and incorporating recycling, the proposed process aligns with Saudi Arabia's Vision 2030 sustainability goals, offering a viable pathway for enhancing economic feasibility and environmental sustainability in aluminum waste management.

Machinability of recycled aluminum alloys

The use of recycled (hereafter called secondary) aluminum alloys is increasing more and more in light of sustainability as the energy needed for their production is much lower than in the case of the primary alloys and they may have mechanical properties comparable to those of the latter. Most of the secondary aluminum alloys are used to fabricate parts through casting processes, which may need further machining operations to get the part’s final shape. While the mechanical properties of the secondary aluminum alloys have been comprehensively addressed in the literature and correlated to the different intermetallic particles that characterize their microstructure, the same is not true when addressing machinability. In this framework, the paper investigates the machinability of one primary and two secondary aluminum alloys in terms of cutting forces and surface finish after turning trials carried out at fixed cutting parameters. A detailed characterization of the alloys’ microstructure was carried out making use of both optical and scanning electron microscopy to identify the size, morphology, and distribution of intermetallics. The highest cutting force was registered when machining the primary alloy, being characterized by the highest specific cutting energy. The surface damage in terms of tearings induced by cutting was comparable between the primary and secondary alloys. In contrast, the different roughness features that characterize the machined surfaces of the considered alloys can be partly ascribed to the different intermetallics they present. Nevertheless, the surface topography analysis results must be interpreted based on the specific application.

Effective reduction of iron impurities in recycled aluminium-silicon alloy type LM-6 through sedimentation and filtration with synthesized Mn, Cr and Zr transition metal powders

Abstract In secondary aluminium recycling, impurity reduction, especially of iron, is a significant challenge as it deteriorates the material quality in the aluminium melt. Recycled aluminium alloys are widely used in various industries, including automotive, marine, and structural engineering. Specifically, LM-6 aluminium alloy is commonly used in automotive engine parts and transmission cases. This research focused on reducing the excessive iron content in LM-6 alloy scrap. Elements like manganese (Mn), chromium (Cr) and zirconium (Zr) were added to the melt in form of synthesized powders to form intermetallic compounds. These powders will also act as grain refiners, neutralizers and reducing the detrimental effects on the alloys. The powders were synthesized using the ball milling method with a ball to powder ratio of (5:1) to enhance mixing and amalgamation with the melt. The melt was held at an optimized temperature of 640 ± 10 °C to promote the formation of intermetallic sludge, encouraging the sedimentation of aluminium-iron (Al-Fe) intermetallic phases. XRD confirmed the formation of AlMn, AlCr, AlZr with other phases. After sedimentation, a glass fabric mesh with a pore size of 200 μm was used to effectively filter out β-iron during the filtration process. This technique reduced iron impurity in the melt by 50%–60%. As a result, the mechanical properties of the recycled aluminium improved significantly: hardness increased by 14%, and tensile strength increased by 36%. The wear and corrosion resistance of the material also improved due to the incorporation of the synthesized powders. SEM analysis revealed the plate-like formation of iron structures and confirmed the presence of the manganese, chromium, and zirconium powders in the metallographic analysis.

Re-manufacturing of Pre-deformed Automotive Sheet Metal Stamping Scrap Without Melting

Abstract The recycling of aluminium sheet metal typically involves shredding and re-melting, processes which are both energy-intensive and challenged by the presence of metallic contaminants. To mitigate these issues, this study explores an alternative approach: the re-manufacturing of deep-drawn parts directly from scrap aluminium sheets, thus bypassing the melting step. We used 2 mm thick Al-Mg sheet metal in H111 temper to produce simulated stamping scrap (miniaturized bonnets). Blanks were cut from these bonnets and secondary parts in a cross-cup geometry were deep-drawn using two different forming processes: warm-forming at 200 °C and O-temper forming at room temperature. The resulting maximum draw depths were 20-22 mm for warm-forming and 25-30 mm for O-temper forming. While warm-forming resulted in lower draw depths, O-temper forming led to coarse recrystallized grain formation in some regions. Our approach could significantly reduce the energy consumption associated with aluminium recycling.

Sustainable recycling of pure aluminum from waste chips under supergravity-enhanced separation: A cleaning process

Large quantities of chips containing high levels of aluminum are always inevitably produced during machining process of aluminum products, which is a valuable renewable resource. In this paper, an environmental-friendly method for direct and continuous recovery of same-level recycled Al from waste chips under supergravity-induced was proposed. The oxide film covering the surface of the molten Al-chips was easily disrupted under super-gravity, and subsequently almost all of Al melt detached from the oxide film and flowed rapidly through the microporous ceramic foam filter, with a yield ratio of more than 97 %. During this process, all fine broken oxide-film particles and large amounts of primary iron-rich particles in the melt were captured in the complex channels of the filter, resulting in clean 1xxx series recycled Al with free inclusions and impurity iron content of less than 0.28 wt%. In addition, a sustainable process and a continuous centrifugal unit for recycling aluminum chips were designed, the economic and environmental advantages of which demonstrate the feasibility of sustainable regeneration of aluminum chip resources on an industrial scale via supergravity technique.

Aluminum Circular Economy in the Bicycle Industry

Abstract From a traditional perspective, Bicycles are considered low-carbon emission transportation tools for commuting and traveling. This study analyzes aluminum recycling pathways within the bicycle manufacturing process to illustrate the bicycle circular economy model for the industry stakeholders to better understand the roadmap for improving from manufacturing to recycling. The goal is to promote the bicycle industry's sustainable development by achieving economic benefits and environmental protection. A comprehensive analysis of the entire lifecycle of the bicycle manufacturing process including production, usage, and recycling, was conducted for future application and manufacturing improvement. This research identifies existing technical barriers, policy limitations and restrictions, and issues related to market acceptance. In response to these challenges, a framework is proposed to draw a roadmap for the industry to make informed decisions on circular-economy-centered practices. This approach encourages companies to improve carbon emission efficiency to contribute to the long-term sustainability of the bicycle industry. JEL classification numbers: L11, M10. Keywords: Carbon Emission Efficiency, Circular Economy, Aluminum Recycling, Sustainability.

3D morphological evolution of the Fe-Rich phase and mechanical properties of the recyclable A356 alloy

Efficient utilisation of recycled aluminium promotes low-carbon and green manufacturing in the aluminium industry. However, the low tolerance of Al for Fe content limits its application. The morphological evolution of the Fe-rich phase and the mechanical properties of recycled A356 alloys with varying Fe contents were investigated using optical microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), synchrotron radiation X-ray computed tomography (SRXCT), and Thermo-Calc thermodynamic calculations. The results show that with increasing Fe content, the morphology of the Fe-rich phase transformed from fine-granular and short rod-like structures into coarse needle-like and Chinese-script. In three dimensions (3D), the larger Fe-rich phases displayed a multibranched structure composed of rod-like and plate-like phases rather than a single morphology. Notably, at an Fe content of 0.4 %, the Fe-rich phases presented Chinese-script and short rod-like shapes in sections but did not significantly change the 3D morphology or type of the Fe-rich phase. However, the Fe-rich phases in the 0.4 %Fe alloy exhibited higher thickness and sphericity, which improved the ductility of the alloy. Thermodynamic calculations indicate that the initial formation temperature of the Fe-rich phase in the 0.4 % Fe alloy overlaps with that of the Al-Si eutectic reaction, which is referred to as the critical Fe content. At the critical Fe content, the ternary eutectic reaction of Al-Si-(AlFeSi) suppressed the rapid growth of the Fe-rich phase and mitigated their negative impact on ductility.

Benchmarking wire-fed and autogenous laser beam welding to study the effect of Cu additions on weld integrity of 6060-T6 aluminium extrusion

In the automotive industry 6xxx aluminium alloys are preferred materials, yet their fabrication contributes to a considerable carbon footprint. A promising strategy to mitigate the environmental impact is the increased utilisation of recycled (secondary) aluminium, sourced from diverse scrap streams. However, as aluminium scraps come from different sources, the intrinsic variability of chemical composition, stemming from uncontrollable levels, poses a challenge, impacting material properties and weldability. Balancing manufacturability while enhancing the adoption of recycled alloys becomes a critical effort. This study aims at benchmarking wire-fed and autogenous laser beam welding to study the effect of Cu inclusions on weld integrity of 6060-T6 extrusion. The paper contributes to show the impact of Cu addition during laser welding of 6060-T6 aluminium alloys. Findings highlighted that the modification of chemical composition using filler wires is currently the most efficient approach to improve joint strength, although the Cu additions tend to reduce the weld strength.

Life cycle assessment of the rolling process of thin aluminum sheets

ABSTRACT Primary aluminum recycling has been demonstrated to play a pivotal role in sustainable manufacturing. Nevertheless, among all the Life Cycle Assessment (LCA) studies existing in the literature on aluminum products, very few focus on the rolling stage. In this work, LCA of two semi-finished products, plates and coated strips, made of AA8011 aluminum alloy have been carried out. Inventory data were collected by the Laminazione Sottile plant, except for coil coating data for pharmaceutical caps, which were collected in the Italcoat plant. For both semi-finished products, hot rolling and fusion mostly affect the environmental impact of the manufacturing. Moreover, results show that the substitution of virgin primary aluminum with secondary aluminum results in a remarkable minimization of the environmental impact. Indeed, a 50% reduction of primary aluminum results in about a 70% reduction of GWP to produce AA 8011 coated strips.

Modelling and optimization of an innovative facility for automated sorting of aluminium scraps

The growing demand for aluminium worldwide makes aluminium recycling critical to realising a circular economy and increasing the sustainability of our world. One effective way to improve the impact of aluminium recycling is to develop cost-efficient automated sorting technologies for obtaining pre-defined high-quality aluminium scrap products, thus reducing undesirable downcycling and increasing environmental/economic benefits. In this work, an innovative facility, which includes singulation, sensor scanning, and ejection, is optimised for the automated sorting of aluminium scraps. The sorting facility is computationally studied by a virtual experiment model based on the discrete element method. The model considers particle-scale dynamics of complex-shaped scraps and mimics the automated operation of the facility. Based on virtual experiment modelling, the flow of scrap is optimized by computation, with the feasible operation of the sorting facility being proposed. Accordingly, the sorting facility has been built and model predictions are confirmed in actual operation.

Sustainable recycling of aluminum scraps to recycled aerospace-grade 7075 aluminum alloy sheets

The production of aerospace-grade aluminum alloy sheet is characterized by stringent demands, resulting in a low yield rate. The processing of this material generates considerable amounts of highly alloyed scrap, complicating its recycling due to the challenge of maintaining melt cleanliness. This study employed an aerospace-grade melt refining system to purify the recycled 7075 alloy melt obtained from comprehensive scrap remelting. The melt's cleanliness was assessed using Porous Disc Filtration Analysis (PoDFA) and Liquid Metal Cleanliness Analyzer (LiMCA) and Alscan. The microstructure of the ingots and sheets was examined through Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD), whereas the mechanical properties of recycled sheets were evaluated and benchmarked against those of primary sheet at an aerospace-certified testing facility. The findings indicate that the recycled 7075 sheet meets aviation standards, with no significant differences in microstructure or performance when compared to primary sheet. Furthermore, the study highlights the economic benefits of recycling scrap, revealing a potential cost saving of $4210.8 per ton of recycled sheet. The findings presented herein offer a theoretical framework and empirical evidence supporting the development of a recycling system for aerospace scraps and the certification of airworthiness for recycled aerospace aluminum alloy.

Performance of Solar Collector Using Recycled Aluminum Cans for Drying

Performance of Solar Collector Using Recycled Aluminum Cans for Drying

FLAx‐REinforced Aluminum (FLARE): A Bio‐Based Fiber Metal Laminate Alternative Combining Impact Resistance and Vibration Damping

Fiber metal laminates (FMLs) have mainly been used in aerospace applications with synthetic fibers. To improve their environmental credentials and address issues regarding the end‐of‐life of these materials, a shift to FMLs based on natural fibers can be a promising course of action. However, regarding them as conventional FMLs overlook some of the unique benefits of natural fibers. Therefore, this study pioneers the examination of FLAx‐REinforced aluminum (FLARE) for its combined impact resistance and vibration damping. Dynamic mechanical analysis and vibration beam tests demonstrate that the metallic layer predominantly influences the damping behavior of FLARE. The loss factor notably decreases with aluminum addition (by 80% compared to the flax composite), approximated via an inverse mixture rule. Low‐velocity impact tests highlight the role of aluminum layers in energy absorption and the composite strength as a critical factor in impact resistance. FLARE exhibits 25% less specific energy absorption compared to its glass fiber counterpart. A quasi‐static analytical model suggests the potential of FLARE for practical applications. With its balance of properties and considering its potential advantages at end‐of‐life, allowing recycling of aluminum, and its expected lower carbon footprint, FLARE renders potential beyond the aerospace sector, e.g., in other forms of transportation.

Numerical Study on the Effect of Geometrical Changes on the Deformation Behaviour of Recycled Aluminium Alloy AA6061 undergoing High Velocity Impact using Hyperworks-Radioss

Numerical analysis is important to predict material behaviour without require an experimental implementation. This manuscript focuses on a numerical prediction establishment of a direct recycled aluminium alloys AA6061 undergoing Taylor Cylinder Impact test using Johnson-Cook model in HyperWorks Radioss. The numerical setup was first validated against the experimental data at the velocity range of 179 to 212 m/s. Good agreement between simulation and experimental data was obtained within the range that exhibits a mushrooming shape fracture mode. A parametric study was then conducted to study the deformation behaviour of the selected recycled aluminum alloys within the validated range at various geometrical settings. The analysis was made by focusing on the post-impact configuration of the projectile at different impact velocities in terms of residual length, deformed diameter, and the final length-to-diameter ratio. It was found that a broader projectile experienced a less significant reduction in its final length (Lf/Lo goes from 0.87 to 0.9 for projectile diameter 9mm to 34mm) and a smaller increase in the deformed diameter compared to a thinner projectile (Df/Do goes from 1.18 to 1.12 for projectile diameter 9mm to 34mm). It was found that a thinner projectile experienced more diameter expansion than length reduction post impact. In addition, a longer projectile experienced more residual length reduction (Lf/Lo goes from 0.92 to 0.87 for projectile length 2mm to 14mm) and more radial deformation compared to the one with a smaller initial length (Df/Do goes from 1.06 to 1.18 for projectile length 2mm to 14mm). All projectiles showed more significant changes on the deformed diameter compared to the changes in residual length post-impact. The results helped the understanding of a critical aspect of the deformation behaviour of recycled aluminum alloy AA6061 more effectively compared to experimental work implementation.

Kinetics of Active Seed-Induced Al(OH)3 Precipitation from NaAlO2 Solution for Recycling Aluminum from Spent Lithium-Ion Batteries

Kinetics of Active Seed-Induced Al(OH)₃ Precipitation from NaAlO₂ Solution for Recycling Aluminum from Spent Lithium-Ion Batteries

Exploring the paths of energy conservation and emission reduction in aluminum industry in Henan province, China

As the world's largest producer and consumer of aluminum, China's aluminum industry is facing enormous pressure for energy conservation and emission reduction due to its traditional high energy consumption, high emissions, and high pollution. To explore the green and low-carbon development path of the aluminum industry, an integrated modelling framework was developed, including aluminum production forecasting and scrap recycling model, energy consumption-carbon emission-air pollutant emission model, and conservation supply curve method. Five different scenarios were set up to evaluate the energy saving and emission reduction potential of Henan Province from 2023 to 2050, by adopting four measures of accelerating the recycled aluminum, promoting energy efficiency technologies, expanding the scale of electrolytic cells, and increasing the share of renewable energy. The results showed that the production of alumina and primary aluminum decreased to 9.6 and 1.8 Mt respectively in 2050, while the future production of aluminum processing products and recycled aluminum showed a continuous upward trend. By 2050, production of recycled aluminum will increase to 14.0 Mt, expanding by about 5.7 times compared to 2022. The energy-saving and emission reduction potential of the integrated scenario is the most significant, with energy consumption, CO2, SO2, NOX, PM10, PM2.5 and fluoride decreased by 54.3, 73.0, 96.5, 72.7, 82.6, 82.6, and 98.9% compared to the business-as-usual scenario, respectively. The results also indicated that accelerating the recycled aluminum and optimizing energy structure are more effective for mitigation. Finally, policy suggestions for mitigating energy consumption and pollutant emissions of the aluminum industry in Henan Province were proposed. The systematic framework of this study can be widely applicable to other provinces and the whole country, which can provide some references for the aluminum industry to achieve the carbon peak and carbon neutrality targets.