Light Metal Research Articles

Crystal Chemistry at Interfaces Between Liquid Al and Polar SiC{0001} Substrates

Silicon carbide (SiC) has been widely added into light metals, e.g., Al, to enhance their mechanical performance and corrosion resistance. SiC particle-reinforced metal matrix composites (SiC-MMCs) exhibit low weight/volume ratios, high strength/hardness, high corrosion resistance, and thermal stability. They have potential applications in aerospace, automobiles, and other specialized equipment. The macro-mechanical properties of Al/SiC composites depend on the local structures and chemical interactions at the Al/SiC interfaces at the atomic level. Moreover, the added SiC particles may act as potential nucleation sites during solidification. We investigate local atomic ordering and chemical interactions at the interfaces between liquid Al (Al(l) in short) and polar SiC substrates using ab initio molecular dynamics (AIMD) methods. The simulations reveal a rich variety of interfacial interactions. Charge transfer occurs from Al(l) to C-terminating atoms (Δq = 0.3e/Al on average), while chemical bonding between interfacial Si and Al(l) atoms is more covalent with a minor charge transfer of Δq = 0.04e/Al. The prenucleation at both interfaces is moderate with three to four recognizable layers. The information obtained here helps increase understanding of the interfacial interactions at Al/SiC at the atomic level and the related macro-mechanical properties, which is helpful in designing novel SiC-MMC materials with desirable properties and optimizing related manufacturing and machining processes.

A DFT Study of Band-Gap Tuning in 2D Black Phosphorus via Li+, Na+, Mg2+, and Ca2+ Ions.

Black phosphorus (BP) and its two-dimensional derivative (2D-BP) have garnered significant attention as promising anode materials for electrochemical energy storage devices, including next-generation fast-charging batteries. However, the interactions between BP and light metal ions, as well as how these interactions influence BP's electronic properties, remain poorly understood. Here, we employed density functional theory (DFT) to investigate the effects of monovalent (Li+ and Na+) and divalent (Mg2+ and Ca2+) ions on the valence electronic structure of 2D-BP. Molecular orbital analysis revealed that the adsorption of divalent cations can significantly reduce the band gap, suggesting an enhancement in charge transfer rates. In contrast, the adsorption of monovalent cations had minimal impact on the band gap, suggesting the preservation of 2D-BP's intrinsic electrical properties. Energetic and charge analyses indicated that the extent of charge transfer primarily governs the ability of ions to modulate 2D-BP's electronic structure, especially under high-pressure conditions where ions are in close proximity to the 2D-BP surface. Moreover, charge polarization calculations revealed that, compared with monovalent cations, divalent cations induced greater polarization, disrupting the symmetry of the pristine 2D-BP and further influencing its electronic characteristics. These findings provide a molecular-level understanding of how ion interactions influence 2D-BP's electronic properties during ion-intercalation processes, where ions are in close proximity to the 2D-BP surface. Moreover, the calculated diffusion barrier results revealed the potential of 2D-BP as an effective anode material for lithium-ion, sodium-ion, and magnesium-ion batteries, though its performance may be limited for calcium-ion batteries. By extending our understanding of interactions between ions and 2D-BP, this work contributes to the design of efficient and reliable energy storage technologies, particularly for the next-generation fast-charging batteries.

Harnessing Machine Learning for Effective Waste Classification and Recycling

The world produces nearly 3.5 million tons waste every day so it is important to improve waste management and recycling system. This paper defines how machine learning can classify waste, specifically using VGG16 CNN model to classify 9 types of recyclable materials such as light bulbs, paper, plastic, organic, glass, batteries, clothes, metal and e-waste .We had used nearly 8000+ images from Google Images and Dreamstime.com to test VGG16 model and compare it with another model named as Inceptionv3. But Inceptionv3 showed higher accuracy (~90%) ,and it did not work well when tested on real data. In contrast, the VGG16 model which initially had lower accuracy of (~70%), performed better when tested on real-world scenarios. We also developed a web application which not only classifies the waste but also provides the valuable information to help people how to minimize waste reduction and maximize recycling. The classified images of the waste and its respective findings will also be shared with local authorities to enhance better recycling efforts. Hence this study focuses on need to select right models for waste classification and suggests looking into another machine learning techniques in future.

Electron work function guided tailoring of (W4-x, Mx)C4 /doped Ni matrix interfacial bonding: Insights from first-principles calculations

Heavy tungsten carbide (WC) may cause inhomogeneous distributions in WC-metal matrix composite hardfacing overlays, thus negatively affecting its performance as reinforcement. WC can be lightened by partially substituting W with lighter metals, e.g., Mo and Cr, while maintaining its strength. However, the bonding between modified WC and matrix metals such as nickel (a typical metal-matrix for overlays) is uncertain. This article reports a study on the interfacial bonding between (W4-x, Mx)C4 (M=Mo or Cr) and Ni matrix via first-principle calculations. Different atomic interactions i.e., metal-metal and metal-carbon interactions, at the interface were studied to understand the interfacial bonding through analyses of electron work function (EWF), electron localization function, electronic density of states, bond order, and net charge. It was demonstrated that the lighter (W4-x, Mx)C4 carbides exhibit strong bonding with Ni, comparable to or even stronger than that of WC/Ni interface, and the interfacial bonding includes covalent, ionic and metallic bond components. It is demonstrated that the interfacial bonding can be tuned by doping elements in the Ni matrix with different EWFs, e.g., Mn, Cu, Au, Pt, and Se. Efforts have been made to verify a hypothesis that EWF is an indicator, which can be used to guide selecting effective dopants for tailoring the interfacial bond strength.

A machine-learned kinetic energy model for light weight metals and compounds of group III-V elements

Abstract We present a machine-learned (ML) model of kinetic energy for orbital-free density functional theory (OF-DFT) suitable for bulk light weight metals and compounds made of group III–V elements. The functional is machine-learned with Gaussian process regression (GPR) from data computed with Kohn-Sham DFT with plane wave bases and local pseudopotentials. The dataset includes multiple phases of unary, binary, and ternary compounds containing Li, Al, Mg, Si, As, Ga, Sb, Na, Sn, P, and In. A total of 433 materials were used for training, and 18 strained structures were used for each material. Averaged (over the unit cell) kinetic energy density is fitted as a function of averaged terms of the 4th order gradient expansion and the product of the density and effective potential. The kinetic energy predicted by the model allows reproducing energy-volume curves around equilibrium geometry with good accuracy. We show that the GPR model beats linear and polynomial regressions. We also find that unary compounds sample a wider region of the descriptor space than binary and ternary compounds, and it is therefore important to include them in the training set; a GPR model trained on a small number of unary compounds is able to extrapolate relatively well to binary and ternary compounds but not vice versa.

Harnessing synergy of spin and orbital currents in heavy metal/ferromagnet multilayers

Spin-orbitronics, exploiting electron spin and/or orbital angular momentum, offers a powerful route to energy-efficient spintronic applications. Recent research on orbital currents in light metals broadens the scope of spin-orbit torque (SOT). However, distinguishing and manipulating orbital torque in heavy metal/ferromagnet (HM/FM) remains a challenge, limiting the promising synergy of spin and orbital currents. Here, we design a HM/FM/FMSOC heterostructure and experimentally separate orbital torque contribution from spin torque by utilizing the distinct diffusion length of spin and orbital currents. Furthermore, we achieve the synergy of spin and orbital torques by controlling their relative strength, and obtain a 110% improvement in torque efficiency compared to the representative Pt/Co bilayer. Our findings not only contribute to a deeper understanding of SOT mechanisms and orbital current transport in HM/FM multilayers, but also highlight the promising prospect of orbital and spin torque synergy for optimizing the efficiency of next-generation spintronic devices.

Uncovering efficient sensing properties of vanadium disulfide (VS2) nanosheets towards specific neurotransmitters: A DFT prospective

Designing efficient nanosensors based on ultrathin materials for the detection of neurotransmitters is crucial for biosensing applications. In this work, using spin-polarized density functional theory (DFT) calculations, structural, electronic, magnetic, and adsorption of the selected neurotransmitters, such as dopamine (DA) and histamine (HA), were investigated using light transition metals dichalcogenides, vanadium disulfide (VS2) nanosheets. It was revealed that DA and HA adsorbed relatively weakly on pristine (p-VS2) as well as single sulfur (S) Vacancy-induced (SV-VS2). However, the introduction of selected transition metals (TMs) dopants, such as cobalt (Co), iron (Fe), and nickel (Ni), significantly improved the adsorption of DA and HA. Among the studied systems, Ni-doped VS2 (Fe-doped VS2) exhibited the strongest adsorption toward DA (HA) with an adsorption energy of −2.00 (−1.28) eV, which is promising for practical sensing applications. Charge analysis revealed that both DA and HA acted as charge donors to the TMs-doped VS2. Upon DA/HA adsorptions, quantifiable variations were observed in the electronic structures and magnetic properties of TMs-doped VS2, which were studied through band structures, spin-polarized density of states, and work function calculations. Lastly, for the practical detection capabilities at diverse pressure and temperature settings, we employed the Langmuir adsorption model. It was found that TMs-doped VS2 detected DA and HA at concentrations ranging from tens of ppt to ppm levels, respectively. We strongly believe that our findings will contribute towards the development of highly effective nanosensors based on TMs-doped VS2 nanosheets for the detection of DA, and HA.

Study on the effect of Lorentz force on the nuclear reactor core melt stratification in electromagnetic cold crucible

To understand the effect of the Lorentz force on core melt stratification during experiments, a multi-physical field coupling model of electromagnetic induction, non-isothermal flow, and two-phase flow is established in this paper. The evolution of the layered core melt in the electromagnetic cold crucible is studied for different relative densities and phase volume fraction ratios between metal and oxide. The calculation results show that the coupling model can accurately describe the structural evolution of core melt. The Lorentz force cannot change the relative positions of the metal and oxide, but it can significantly affect the morphology of the core melt. If the density of the metal is less than that of the oxide, the Lorentz force causes the light metal with a small phase volume fraction to form a hemispherical shape in the top center of the crucible. As the phase volume fraction increases, the Lorentz force become weaker than those of gravity and buoyancy. The light metal is then flat. When the metal density is greater than the oxide density, the Lorentz force causes the heavy metal with a small phase volume fraction to appear as a hemisphere, but causes the heavy metal with a large phase volume fraction to appear as an ellipsoid in the lower part of the crucible.

Chemical abundances of 20 barium stars from the OHP spectra

ABSTRACT Based on the high resolution and high signal-to-noise spectra, we derived the chemical abundances of 20 elements for 20 barium (Ba-) stars. For the first time, the detailed abundances of four sample stars, namely HD 92482, HD 150430, HD 151101, and HD 177304 have been analysed. Additionally, Ba element abundance has been measured using high-resolution spectra for the first time in six of the other 16 sample stars. Based on the [s/Fe] ratios, the Ba-unknown star HD 115927 can be classified as a strong Ba-star, while the Ba-likely star HD 160538 can be categorized into a mild Ba-star. Consequently, our sample comprises three strong and 17 mild Ba-stars. The light odd-Z metal elements and Fe-peak elements exhibit near-solar abundances. The [$\alpha$/Fe] ratios demonstrate decreasing trends with increasing metallicity. Moreover, the abundances of neutron-capture (n-capture) elements show significant enhancements in different degrees. Using a threshold of the signed distances to the solar rapid-process (r-process) abundance pattern $d_{\rm s}$ = 0.6, we find that all of our sample stars are normal Ba-stars, indicating that the enhancements of slow-process (s-process) elements should be attributed to material transfer from their companions. We compare the observed n-capture patterns of sample stars with the FRUITY models, and estimate the mass of the Thermally-Pulsing Asymptotic Giant Branch stars that previously contaminated the Ba-stars. The models with low masses can successfully explain the observations. From a kinematic point of view, we note that most of our sample stars are linked with the thin disc, while HD 130255 may be associated with the thick disc.

Preface: 13th Ranshofener Leichtmetalltage

Abstract What strategies are available to minimize resource consumption in the light metal industry through recycling and energy efficiency? How can lightweight design make mobility more sustainable? And what role will artificial intelligence play in future processes in the metal processing industry? These and other questions are addressed at the 13th Ranshofener Leichtmetalltage 2024, which take place on the 26th–27th of September 2024 at the Hotel Gut Brandlhof in Saalfelden, Austria, and are organized in accordance with the criteria of the Austrian Ecolabel for Green Events. Under the guiding theme of “Light Metals Innovations for Environmental and Economic Sustainability”, this year’s conference offers an exciting program in three sessions “Digitalization in the Context of Circularity”, “Sustainable Process Development” and “Innovative Light Metals and their Characterization”. The focus is on decarbonization and digitalization in process and material development as well as the material characterization of light metals. A balanced spectrum of international presentations from universities, RTOs and industry provides participants with an up-to-date overview of the latest scientific findings and successful light metal applications. The 13th Ranshofener Leichtmetalltage 2024 are thus clearly focused on decarbonization and digitalization – even in times of diverse challenges. The first session, “Digitalization in the Context of Circularity”, highlights best-practice examples from the aluminium industry, the balance between sustainability and performance in metal processing and the implementation of complex geometries using wire-based additive manufacturing. The second session, “Sustainable Process Development”, is dedicated to the decarbonization and reduced material consumption of industrial processes, for example through GigaCasting, or the use of innovative recycling technologies. The third session, “Innovative Light Metals and their Characterization”, addresses forward-looking topics such as the development of special aluminium alloys for additive manufacturing, the use of old car scrap for innovative alloys and the decarbonization of the magnesium industry. The conference proceedings contain scientific contributions to the conference. We would like to thank all the authors for their high-quality work and the participants of the 13th Ranshofener Leichtmetalltage 2024 for their interest. We wish you stimulating reading and creative impulses! List of Scientific committee, Organizing committee are available in this Pdf.

Harnessing orbital Hall effect for efficient orbital torque in light metal vanadium

The orbital Hall effect depicts the conversion of charge current to orbital current in nonmagnetic materials without spin–orbit coupling. This absence of spin–orbit coupling enables the light metals serve as sources of orbital current exploited as the information carrier to be applied to the information technology. Here, we investigate current-induced torques in vanadium/ferromagnet (V/FM, FM = Fe, Co, Ni81Fe19) bilayers via spin-torque ferromagnetic resonance (ST-FMR) system. The sign reversal confirms that the orbital Hall effect exists in light metal V, and the orbital torque in V/Co and V/Ni81Fe19 bilayers is dominant. By performing the V thickness dependence of conversion efficiency, we determined the orbital diffusion length of 3.61 nm for V. Our experiment demonstrates that light metals can be used as novel materials in spin–orbit devices, and our research focuses on the orbital freedom of the electron and provides new content for the study of orbital dynamics.

Peer Review Statement

Abstract All papers published in this volume have been reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing. • Type of peer review: Single Anonymous • Conference submission management system: Morressier • Number of submissions received: 13 • Number of submissions sent for review: 12 • Number of submissions accepted: 8 • Acceptance Rate (Submissions Accepted / Submissions Received × 100): 61.5 • Average number of reviews per paper: 1.09 • Total number of reviewers involved: 10 • Contact person for queries: Name: Thomas Klein Email: thomas.klein@ait.ac.at Affiliation: LKR Light Metals Technologies, AIT Austrian Institute of Technology

Data Models for Casting Processes – Performances, Validations and Challenges

Abstract Data-driven models with their associated data learning and training schemes can be utilised for the light metal casting processes. This paper presents the basis of data model building processes along with data training and learning exercises for vertical direct chill casting and high pressure die casting (HPDC) applications. The concepts of efficient database building, data translations and sampling, as well as real-time model building and validations are briefly discussed. Rigorous performance studies were additionally carried out for two real-world case studies. Different combinations of data solvers and interpolators are adapted for the model building techniques, while machine learning schemes are used for data trainings.

Development of Advanced Aluminum and Magnesium Alloys: Microstructure, Mechanical Properties and Processing

Mg and Al alloys are the first and second engineering light metals, which are widely used in the aviation, aerospace, navigation, automotive, and electronic fields [...]

Electrowinning of Light Metals from Molten Salts Electrolytes

Light metals such as lithium, sodium, potassium, magnesium and aluminium may be produced by molten salts electrolysis. Aluminium is produced by the Hall-Heroult process by electrolysis in molten salts. It is by far the largest in terms of production volumes and for metals second only to iron and steel, but it carries a very high carbon footprint mainly due to the wide-spead use of electricity based on based on coal. Magnesium is currently produced by silicothermic reduction of MgO according to the Pidgeon process. However, electrolysis in molten chloride electrolytes using MgCl2 as feedstock may return as it is more sustainable. The current Kroll process for producing titanium is energy intensive and requires lots of work as well as having very low productivity. Sodium is produced by electrolysis in a chloride electrolyte. This process may be improved by using sodium oxide as raw material and inert oxygen evolving anode.

Expanding Lightweight Design Potential by Hybrid Joining of Aluminum Sheets with Aluminum Casting Through Compound Sand Casting and Induction Heating

Combining light metals like aluminum to produce lightweight structures offers a high weight‐saving and contributes to a circular economy in automotive car body construction. Compound casting is a promising process for producing car body parts. Difficulties arise in creating metallic continuity between insert and casting. Insert coatings are used to remove the oxide layer and thereby improve the wettability of the melt. This study uses a hybrid joining method to improve the metallic bond between insert and casting. Induction heating differently influences the strength properties of age‐ and nonage‐hardenable inserts. Compression shear tests characterize the metallic bond strength. Microscopic images show the influence of the process variables on the compound quality. Reproducible sound metallic bonding with low scattering is achieved by enhancing the compound casting process through induction and no insert coating. Cast wall thicknesses down to 4 mm contribute to further lightweight potential as they have the same strength level as the reference sample. A decisive factor is the insert temperature in the compound zone. Thereby, insert preheating conditions play a crucial role. Additional heat treatment of hardenable compounds leads to a further increase in metallic bond strength.

Investigation of the media tightness of a microform-fitted plastic/light metal composite

Plastic/metal hybrid components made of amorphous thermoplastics such as polycarbonate and light metals such as aluminum offer potential to be used in modern automotive headlights to meet the high requirements for tolerances and surface quality. A microform-fit joining approach is used to join plastics and metals, which combines the advantages of material-fit and form-fit joining processes while at the same time avoiding some of the disadvantages of the respective joining approaches, such as stress peaks or the use of additional chemicals. For this purpose, the light metal component is microstructured through laser ablation. To ensure the functional safety of electrical components, the media tightness of the hybrid component is tested with a pressure drop test. An influence of the structure arrangement, the structure spacing and the molding compound on the media tightness can be determined. The highest media tightness can be achieved with a ring-shaped structural arrangement in which the microstructures are orientated orthogonally to the outlet direction of the test medium. The media permeability of a ring-shaped structure arrangement with a structure spacing of 500 µm is 0.42 cm3/s for test specimens made of aluminum and polycarbonate. As the value is below the threshold value of 12 cm3/s, watertightness up to an overpressure of at least 0.5 bar can be concluded.

Исследование характера изменения твердости композиционных материалов с алюминиевой матрицей, упрочненной золой кокосовой скорлупы и красным шламом, с использованием анализа Тагучи

Introduction: in present scenario, light and high strength aluminium metal matrix composite are extensively used due to its high mechanical and tribological properties. Aluminium metal matrix composite reinforced with ceramic and industrial waste can customize its mechanical-chemical behavior. The purpose of the work: to create an aluminum matrix composite material using ceramic (primary) and industrial (secondary) waste represented by red mud and coconut shell ash, respectively. The mass fraction of the strengthening phase varied from 5 to 12.5 wt. % respectively with the residual mass percentage of the aluminum alloy. Method of investigation: nine specimens of composite materials were prepared by stir casting. Stirring was carried out at a speed of 50 to 100 rpm for 20 minutes at a temperature of 800 °C. Result and Discussion: the hardness behavior of the aluminum metal matrix composite was studied at an indentation load of 10, 15 and 20 kN. Taguchi method with L27 orthogonal array was selected to conduct analysis of variance (ANOVA) and regression analysis by selecting the mass percentage of red mud and mass percentage of coconut shell ash. The indentation load was used as an input parameter, and the hardness behavior was taken as an output parameter. The signal-to-noise ratio, response rank table, contour plot, and normal probability plot are investigated and it is found that hardness values improve with the addition of both reinforcing components and indenter load. The results show that the hardness value varies from 33.34 HB to 53.44 HB, and the effect of red mud mass percentage is more significant than the indenter load and coconut shell ash mass percentage.

New correlations for focusing effect evaluation of the light metal layer in the lower head of a nuclear reactor in case of severe accident

In case of a severe accident (SA) in a nuclear reactor, the core heats up and materials melt and relocate to the lower head of the vessel. In such configuration, stratification occurs between the oxide and metal phases present in the melt. When the metal phase is lighter than the oxide phase, the maximum heat flux applied to the vessel wall is concentrated at the location of this top metal layer, creating the so-called “focusing effect”. The modelling of the focusing effect is essential for SA codes to properly evaluate the vessel failure time or to demonstrate the vessel integrity, when In Vessel Retention (IVR) strategy is implemented. However, existing correlations used in SA codes for focusing effect modelling have some limitations: if the thickness of the metal layer becomes very small, they predict an extremely high heat flux. Moreover, they were validated with tests using water, whereas the Prandtl number was found to play a significant role in this heat transfer.In this paper, the focusing effect is studied based on 3D Direct Numerical Simulations (DNS) of a cylindrical metal layer, covering all possible metal layer characteristics in terms of geometry and boundary conditions, especially for its top surface where the intensity of radiative heat transfer may vary. The analysis of the fluid behavior and the quantitative results obtained allow to derive new correlations and a new model based on the radial profile of the mean temperature of the system and on the radial profile at the top surface. Results at reactor scale confirm the overestimation of existing 0D model used in SA codes for a thin metal layer and highlight the relevance of the proposed model for focusing effect evaluation during transient situations.

Development and Characterisation of a New Die-Casting Die Cooling System Based on Internal Spray Cooling

Against the backdrop of climate policy goals and the EU’s aim for a resource-efficient economy, the foundry industry must rethink product range, energy consumption, and production technologies. Light metal casting, which is performed through processes like gravity die casting and high-pressure die casting, requires effective thermal management, which is crucial for optimising mould filling, solidification, cycle times, and part quality. Against this background, this study presents the development and characterisation of a cooling system that completely dispenses with energy-intensive heating/cooling devices. The system is based on a mask shape combined with internal spray cooling. This paper shows the simulation workflow for developing the mould mask and the design of the cooling system and compares the performance with conventional temperature control using channels. In the tests, an 82% higher cooling rate was achieved with Cool-Spray than with conventional temperature control, which was approx. 2.5 mm below the cavity surface. In addition to the more dynamic temperature control, the potential for process control was utilised, and the component quality of the test part was significantly improved compared to conventional temperature control.