Alloy Scrap Research Articles

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.

Preparation of WO3/MoO3-x composites from W–Mo alloy scrap and it's adsorption-photocatalytic properties

A straightforward hydrothermal method was employed to fabricate WO3/MoO3 composites, with the addition of ascorbic acid (Vc) for modification, resulting in WO3/MoO3 composites with oxygen defects (WO3/MoO3-x). WO3/MoO3-x exhibits exceptional adsorption-photocatalytic properties, demonstrating strong adsorption capability for dyes achieved through hydrogen bonding and electrostatic interactions. For all products, adsorption rates for methylene blue (MB) exceeded 95 % when reaching adsorption equilibrium. Moreover, an increase in molybdenum (Mo) content endows the samples with enhanced adsorption capacity for methyl orange (MO) and improved photocatalytic performance. Dynamic fitting of the samples revealed that when the W/Mo molar ratios is 2:8, the product W2Mo8-Vc, exhibits the highest photocatalytic activity. After 3 h of illumination, W2Mo8-Vc achieves a remarkable photocatalytic efficiency of 98 % for dyes. This research not only successfully recycles W–Mo alloy scrap but also yields WO3/MoO3-x composites with adsorption-photocatalytic properties, offering a novel approach for the recycling of W–Mo secondary resource.

Study on the Migration Patterns of Oxygen Elements during the Refining Process of Ti-48Al Scrap under Electromagnetic Levitation.

This study investigated the migration patterns of oxygen in the deoxidation process of Ti-48Al alloy scrap using electromagnetic levitation (EML) technology. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed to analyze the oxygen distribution patterns and migration path during EML. The refining process resulted in three types of oxygen migration: (1) escape from the lattice and evaporation in the form of AlO, Al2O; (2) formation of metal oxides and remaining in the alloy melt; (3) attachment to the quartz tube wall in the form of metal oxides such as Al2O3 and Cr2O3. The oxygen content of the scrap was dropped with a deoxidation ratio of 62%. It indicated that EML can greatly promote the migration and removal of oxygen elements in Ti-Al alloy scrap.

Investigation of the Microstructure and Dry-Sliding Wear Behavior of Co Containing Al-Si-Fe Scrap Alloy

This study investigates the influence of cobalt (Co) addition on the microstructural and wear properties of an aluminum (Al) scrap alloy containing high iron (Fe) impurity content (3%). Microstructural analysis using scanning electron microscopy and optical microscopy confirmed the presence of Co in Fe-rich intermetallics. Upon increasing the Co concentration, β-Al5FeSi phase was seen to be refined without significant morphological modifications. Furthermore, Co addition promoted the formation of a new quaternary phase Al32Si7Fe4Co phase, which was finely distributed throughout the microstructure and acts as a tribo-layer in the Al scrap alloy, offering enhanced wear resistance and improved stability against wear. Standard EN-31 steel disk with compositions chromium (Cr)-1.6%, manganese (Mn)-0.75%, silicon (Si)-0.35%, and carbon (C)-0.9% was used for the wear test. Microhardness and wear properties were evaluated for both the as-cast and heat-treated alloys, with the as-cast samples exhibiting superior wear resistance and a lower coefficient of friction compared to the T6 heat-treated samples. Addition of Co showed refinement in the β-Fe rich intermetallics over the morphological modifications. Similarly, Co addition enhanced the hardness and wear resistance in the as cast alloys. This work provides a detailed analysis contributing significant understandings into the wear mechanisms and potential applications of Co modified recycled Al in various industrial sectors.

Advanced design and optimization of tailored refining fluxes for the purification of Mg–Li alloys

This study systematically investigates the influence of integrating KCl into the refining flux on the purification efficiency of Mg–Li alloy. The findings reveal that an optimal purification effect is achieved with a 50 % addition of KCl to the refining flux, resulting in a remarkable 56 % reduction in volume fraction of inclusions to 0.17 % and an 80 % improvement in elongation to 29.1 %. The developed novel quaternary refining flux is composed of KCl + LiCl + LiF + CaF2 (3:3:1:2, wt.%). Based on thermodynamic calculation and analysis, the purification mechanism is elucidated, demonstrating that KCl enhances purification efficiency by reducing flux and melt viscosity, improving wettability, increasing contact area, and facilitating flux adsorption on inclusions. Excessive KCl addition hinders purification by decreasing flux density, slowing settling velocity, and affecting the purification process. The quaternary flux, applying to industrial Mg–Li alloy scrap, demonstrates outstanding purification performance with a 73 % reduction in inclusion volume fraction to 0.33 % and a remarkable 584 % increase in elongation to 17.1 %. The development and application of a novel Mg–Li alloy flux are of significant importance for promoting the industrial development of Mg–Li alloys.

Research on directional solidification combined with electron beam melting and refining for recycling of FGH4096 alloy scraps

The constraints of traditional manufacturing techniques have led to the generation of a considerable amount of waste superalloy, causing substantial resource wastage. The primary concern with waste superalloys lies in the excessive presence of inclusions and impurity elements, rendering them unsuitable for further utilization. This study proposes the use of directional solidification combined with electron beam melting and refining (EBMR) to prepare FGH4096 superalloy ingots (Φ120 mm), which offers a promising approach to produce large-sized powder superalloy master alloy ingots with high-purity and high homogeneity. It is found that the secondary dendrite arm spacing and the size of the γ’ phase in the alloy are significantly reduced after EBMR treatment. The concentration of O and N can be decreased to 5.7 and 0.6 ppmw, respectively. The size of inclusion can be reduced below 8.69 μm and the inclusion numbers reduce by over 50 % compared with both conventional ingots. A droplet transfer mode and melt convection mode mechanism have been proposed, which accurately predicts the melting temperature and melt flow. A quantitative study is conducted on the influence of inclusion density, the contact angle between inclusions and melt, and the surface tension of the melt on capillary forces. The results indicate that the capillary forces between inclusions in the melt range from 1.8 × 10−19 N and 1.9 × 10−17 N. Furthermore, the collision-aggregation behavior of inclusions in the melt is discussed, and an estimate of the tendency of inclusion collision-aggregation is provided. The enrichment of inclusions in the EBMR ingot is primarily the result of turbulent collision. The Marangoni effect and the extremely high surface temperature of the melt promote the collision and agglomeration of inclusions, causing them to accumulate rapidly at the melt surface. Moreover, the thorough removal of inclusions through the decomposition and dissolution process of the electron beam offers theoretical backing for the preparation of superalloys through electron beam melting and high-purity refining.

More resource efficient recycling of copper and copper alloys by using X-ray fluorescence sorting systems: An investigation on the metallic fraction of mixed foundry residues.

According to the state of the art, most of the mixed copper and copper alloy scrap and residues are processed in a copper smelter. Despite the environmental and economic advantages relative to primary production, the recycling of copper and its alloying elements (zinc, tin, lead, nickel, etc.) requires significantly more energy and cost than remelting unmixed or pure scrap fractions such as separate collected material or production scrap. To date, however, less attention has been given to the mechanical purification of mixed scrap. Therefore, sorting by alloy-specific components (SBASC) using an industrial X-ray fluorescence (XRF) sorting system was tested on the coarse metallic fraction (10-32 mm) of mixed foundry residues. The findings show that XRF-SBASC can recover higher-grade copper concentrates (reaching 98.3% Cu), leaded brass and complex alloys, such as aluminium bronze and red brass with high purities, for the use in the production of new materials. XRF-SBASC can therefore contribute to a more resource efficient metal recycling, mainly by reducing the energy consumption and loss levels in copper metallurgy.

LOW CARBON FOOTPRINT ALUMINIUM COMPONENTS FOR E-MOBILITY

In the fast-evolving E‐mobility transformation, the circular economy is one of the key factors to make Europe carbon neutral by 2050, together with sustainability, achievable only with a synergic approach, from raw material choice to recycling, through product design for re‐purposing. Secondary aluminium alloys have a twenty times lower carbon footprint than primary metals, leading to significant CO2 savings. Their properties can satisfy engineering targets through optimized product design. Adopting a smart system layout, in which functions are assigned to assemblies, some of the low‐end mechanical properties of secondary alloys can be offset. Design for easy disassembling can then guarantee a selective re‐purposing and, finally, an environmentally friendly recycling of components. Innovative products in this field have been developed and successfully produced by means of an optimized high-pressure die casting (HPDC) technology, adopting low carbon footprint raw materials supplied in alternative to ingot format. In this work, the characterization of a component for e-mobility has been conducted, evaluating both the characteristics of the scrap alloy used to produce the castings and the casting itself. The results demonstrate a fine and high-quality microstructure of the casting, proving the feasibility of the production process using exclusively scrap alloy.

An electrochemical approach to converting alloy scraps to (FeCrNiMnX)3O4 high-entropy oxides for lithium-ion batteries

Alloy scraps containing plenty of Ni, Cr, Mn, and Fe are promising secondary sources, however, it is still difficult to valorize them due to the high corrosion resistance and mechanical strength and the multi-step processes of separation and purification. Herein, we employed an electrochemical oxidation approach to converting alloys scraps to porous transition metal oxides (TMOs) in highly corrosive molten salts. The resultant TMOs are directly used as feedstocks to synthesize quaternary medium-entropy (FeCrNiMn)3O4 and a series of spinel (FeCrNiMnX)3O4 (X = Zn, Ti, Nb, Sb, Bi, W, and Zr) oxides via solid-state reaction. When employed as anodes for Li-ion batteries (LIBs), the reversible capacity the (FeCrNiMnZn)3O4 reaches 636.4 mAh g−1 at 500 mA g−1 after 250 cycles and the rate capacity reaches 252.4 mAh/g after 2000 cycles at 3 A g−1. The good Li-storage performance is thanks to their excellent electronic conductivity and milder volume change. This work provides a facile route for the direct recovery of full components from alloy scraps and gives insights into the design of HEOs with different elements.

Recovery of W–Mo Alloy Scrap and the Photochromic Properties of WO3/MoO3 Composite Products

Recovery of W–Mo Alloy Scrap and the Photochromic Properties of WO₃/MoO₃ Composite Products

Effect of Superheat on Microstructure and Mechanical Properties of Al-7Si-2Fe Alloy

Recycling of aluminum (Al) alloys is critical to meet the demands of global net zero emission targets. The major challenge in the recycling of Al alloys is the presence of a higher content of iron as an impurity in Al alloy scraps, which deteriorates the mechanical properties of recycled alloys. In the present work, Al-7%Si alloys and Al-7%Si-2Fe alloys were cast at three different superheat temperatures to study the effect of superheat on the formation of iron intermetallic particles in these alloys. Microstructure–mechanical properties correlations were carried out using SEM-EDS and tensile testing of the alloys. 3D x-ray computed tomography (XCT) results show that the β-phase intermetallic particles were observed to be large and platelet-shaped in the Al-7Si-2Fe alloy cast at 700°C, while these particles appeared to be finer and uniformly distributed throughout the sample in the alloy cast at 900°C. XCT results show the presence of large shrinkage porosity in the Al-7Si-2Fe alloy cast at 700°C, due to the presence of large intermetallic particles which hinder the flow of molten metal during solidification of the alloys. Tensile test results show that the addition of 2% iron resulted in a significant reduction in the elongation of the alloy at all superheat temperatures.

Recycling of Magnesium Alloy Scrap by Remelting and Chemical De-coating Process

The growing demands of magnesium (Mg) based materials had risen new challenges related to disposal of unused parts and a huge amount of waste made by such metals. Attempts to recycle the scrap of these materials through remelting had become one of the preferred choices. However, a series of preliminary steps should be carried out to reduce the impurities as well as to maintain the quality of the casted ingot, for instance, by applying de-coating for removing paints or coating substrates at the scrap surface prior to remelting. In this research, the effects of chemical reagent de-coating on the properties of ingot obtained from recycling Mg scrap were studied. A commercial paint removal liquid was preferred as the reagent for removing paint layers over the Mg scrap surface. The de-coated scrap was then remelted in a conventional furnace with NaCl powder as the fluxing layer. The results of this study noticed the importance of chemical de-coating process to reduce the impurity contents in the ingot which might be originated from the coating or paint substrates covering the Mg scrap. Meanwhile, the density and hardness of the Mg ingot processed without de-coating were obviously higher than that had been cleaned previously with paint removing agent.

Removal of Fe impurities from Al alloy scraps by electromagnetic directional solidification combined with Si addition

The removal of Fe from Al alloy scraps is the main challenge for their recycling because the excess of Fe usually forms needle-like phases in the Al alloys, which reduces their mechanical properties. In this study, a combined process of electromagnetic directional solidification and Si addition is proposed to remove the Fe impurities from Al alloy scraps. The influence of the Si content on the removal and distribution of Fe impurities and the removal mechanism of Fe impurities were studied during the electromagnetic directional solidification of Al alloy scraps. In addition, the precipitation pattern of various phases and the removal mechanism of Cu, Mn, Mg, and Zn impurities were studied. The obtained results showed that adding 5–11.4 wt% Si during the electromagnetic directional solidification of Al alloy scrap can promote the precipitation of large bulk α-Fe (Al15(Fe, Mn)3Si2) phase at the bottom and top of the alloy. In other words, Fe and Mn were mainly enriched at the bottom and top of the alloy, which caused the removal of Fe and Mn impurities (Fe and Mn were reduced from 1.1 to 0.32 wt% and from 0.73 to 0.15 wt%, respectively). After the bulk α-Fe phase precipitated, the Al, Chinese script-like α-Fe, Si, θ (Al2Cu), and Q (Al3Cu2Mg9Si7) phases would sequentially precipitate. In the electromagnetic directional solidification, the Mg impurities (from 1.2 to 0.65 wt%) and Zn impurities (from 1.7 to 0.03 wt%) were also removed. This study provides a new green process for the efficient Fe removal from Al alloy scraps.

The Effect of Heat Treating and Deformation by Rolling and Forging on the Mechanical Properties of the 4032-Type Alloy Prepared from Recycled Materials

In the present work, the relationship between deformation, microstructure and mechanical properties of the Sr-modified 4032-type eutectic aluminum alloy was studied. The alloy was prepared from recycled materials, mainly from maritime and automotive 356 alloy scrap samples. Solubilizing heat treatment was carried out at a temperature of 450 °C with a holding time of 8 h. Finally, different samples were subjected to rolling and forging processes at a temperature of 450 °C, thus achieving a reduction of 25% of the original thickness. As expected, the microstructure and properties changed significantly due to the deformation processes, where an important factor was the change in the morphology of eutectic silicon, not only produced by the application of deformation, but also on the effect of adding strontium as a modifying agent. The samples were characterized by optical microscopy and scanning electron microscopy, where it was possible to observe not only the effect of strontium on the morphology of eutectic silicon but also the effect of the heat treatment performed. The tensile tests showed that there was indeed a notable increase in the ultimate tensile stress, yield strength, and resistance to fracture, while initial hardness also considerably increased. Finally, the fracture analysis showed that, after thermal treatment and deformation, all the samples analyzed presented a fracture within the ductile regime. It was shown that the combination of deformation and the addition of strontium led to improved globulization of the eutectic silicon.

Efficient purification of scrap 1060 aluminum alloys contaminated with Fe and Si by super-gravity separation

1060 aluminum alloy has been used in high-volume commercial applications and correspondingly the mass of its downgraded recycling after contamination is huge, which is primarily due to the gradual accumulation of impurity elements such as Fe and Si. The separation of excess Fe is considered to be a key step towards the same-level recycling of aluminum alloy scrap with extremely economic and environmental benefits. A supergravity-induced technology was employed to purify the contaminating elements from molten aluminum scraps through Al2O3 CFF (Al2O3 ceramic foam filter). During the filtration process, the premature precipitation of Fe-rich phases and Si particles in the molten aluminum scraps were intercepted near the inner wall of Al2O3 CFF. Resultantly, the removal rate of Fe and Si reached 83.98 % and 49.67 %, respectively, at T = 690 ℃ and G= 30 via Al2O3 CFF of P = 80 ppi with H= 40 mm. A continuously supergravity-induced separation on industrial scale was further performed and the removal rate of Fe and Si were 83.5 % and 48.3 %, respectively.

Anodic Dissolution of Cu-Zn-Ni Alloy Scraps in Copper(II) sulphate solution

Anodic Dissolution of Cu-Zn-Ni Alloy Scraps in Copper(II) sulphate solution

The Fractographic Analysis of Tensile and Fatigue Fracture Surfaces in Secondary A356 Aluminum Alloy with a Higher Concentration of Iron

A significant number of different metals are present in aluminum alloy scrap and waste. Secondary aluminum cast alloys, made by recycling from scrap and waste, have as the main impurity Fe. Fe reduction is a very economically and technologically expensive process and therefore there is a growing interest in researching such materials. Moreover, the higher content of Fe leads to the formation of brittle Fe-rich phases, leading to faster propagation of fracture in castings. Therefore, this study reflected on secondary aluminum cast alloy with a higher concentration of Fe and research their effect on brittle Fe-rich phase formation (in the needle; plate-like form) and propagation of fracture in the castings. This study confirms the increasing amount of needle Fe-rich phases in the melt with higher content of Fe. The increasing amount of such phases leads to the formation of a large number of cleavage fractures on fracture surfaces. Although the cleavage fracture increased, the experimental results show low changes in the properties of all experimental melts.

A new process for efficient purification of 6061 aluminum alloy scrap under semi-solid and super-gravity conditions

A new method for efficient and sustainable recovery of pure Al from 6061 aluminum alloy scrap based on semi-solid processing and supergravity separation was proposed in this study. Firstly, the microstructural variations of the alloy scraps after semi-solid isothermal treatment (SSIT) were investigated, and the liquid phase accumulated with a large amount of impurity elements would gradually aggregate at the grain boundaries and eventually form a dendritic network, while the spherical Al particles within the grain had high purity. Subsequently, the inter-dendritic liquid was successfully extruded from the intergranular by super-gravity separation technology and the pure Al was efficiently recovered. In this process, the effects of separation time (i.e., isothermal treatment time, t), separation temperature (i.e., isothermal treatment temperature, T) and gravity coefficient (G) on the purification effect were evaluated. The recovery rate of pure aluminum (Al ≈ 99.3 wt%) was 81.98% at the optimum conditions of t = 15 min, T = 640 °C, G = 500. In addition, it was found that increasing the separation time and temperature was beneficial to the purification effect of the alloy scrap but had a negative impact on the recovery rate. Therefore, this study has designed a new process for super-gravity purification and recovery, which realized cyclic recycling and significantly improves the recovery efficiency of aluminum scrap.

Microstructure and Mechanical Properties of Tungsten Heavy Alloy Prepared Using Tungsten Metal Powder Produced from Heavy Alloy Scrap

Tungsten metal powder, using a hydrometallurgical route, was extracted from tungsten heavy alloy scrap that was generated during machining of penetrator cores for the manufacture of Fin Stabilised Armour Piercing Discarding Sabot (FSAPDS). The powder was subjected to extensive characterisation that included physical property evaluation and analysis of the alloy chemistry in order to assess its suitability for the preparation of tungsten heavy alloys with enhanced mechanical properties. Subsequently, a tungsten heavy alloy based on W-Ni-Co was consolidated using this powder through liquid phase sintering followed by heat treatment and swaging operations to realize long rods (~500 mm). This was followed by a detailed characterisation that included microstructure and mechanical property. The mechanical properties of these rods are promising, exhibiting a good balance of tensile and impact properties, which in turn underscores the potential of these recycled powders in the production of premium quality heavy alloy long rods for stringent applications such as kinetic energy penetrators.

Evolution Behavior of the Surface Oxide Film of Al Alloy Scraps in the Melt

The oxide film on the scrap surface is one of the primary sources of oxide inclusions in the aluminum melt. Understanding the evolution of the oxide films in the aluminum melt is an important step for developing efficient recycling technologies and controlling the quality of the product. In the present study, we studied the evolution behavior of the oxide film in the aluminum melt. The oxide films were introduced via aluminum alloy scraps into the melt, and the micro-morphology and composition of the oxide film were analyzed by scanning electron microscope and energy spectrum. Results show that the oxide film on the surface of 1235 alloy foil, A356 alloy turning, and 5083 alloy scalping were broken into small flake oxide film and then transformed into minor granular oxide when the scraps were charged into commercial purity aluminum melt. However, in aluminum alloy melt containing magnesium, the oxide film remained an intact sheet shape up to a certain melt dwelling time.