Electromagnetically Modified Filtration of Aluminum Melts—Part I: Electromagnetic Theory and 30PPI Ceramic Foam Filter Experimental Results

In the present work, laboratory-scale continuous filtration tests of liquid A356 aluminum alloy have been performed. The tests were conducted using standard 30 PPI (pores per inch) ceramic foam filters combined with magnetic flux densities (~0.1 and 0.2T), produced using two different induction coils operated at 50Hz AC. A reference filtration test was also carried out under gravity conditions, i.e., without an applied magnetic field. The obtained results clearly prove that the magnetic field has a significant affect on the distribution of SiC particles. The influence of the electromagnetic Lorentz forces and induced bulk metal flow on the obtained filtration efficiencies and on the wetting behavior of the filter media by liquid aluminum is discussed. The magnitudes of the Lorentz forces produced by the induction coils are quantified based on analytical and COMSOL 4.2® finite element modelin

Sampling Procedure, Characterization, and Quantitative Analyses of Industrial Aluminum White Dross

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Characterization of Ceramic Foam Filters Used for Liquid Metal Filtration

In the current study, the morphology including tortuosity, and the permeability of 50-mm thick commercially available 30, 40, 50,and 80pores per inch (PPI) alumina ceramic foam filters (CFFs) have been investigated. Measurements have been taken of cell (pore), window, and strut sizes, porosity, tortuosity, and liquid permeability. Water velocities from ~0.015 to 0.77m/s have been used to derive both first-order (Darcy) and second-order (Non-Darcy) terms for being used with the Forchheimer equation. Measurements were made using 49-mm "straight through” and 101-mm diameter "expanding flow field” designs. Results from the two designs are compared with calculations made using COMSOL 4.2a® 2D axial symmetric finite element modeling (FEM), as a function of velocity and filter PPI. Permeability results are correlated using directly measurable parameters and compared with the previously published results. Development of improved wall sealing (49mm) and elimination of wall effects (101mm) have led to a high level of agreement between experimental, analytic, and FEM methods (±0 to 7pct on predicted pressure drop) for both types of experiments. Tortuosity has been determined by two inductive methods, one using cold-solidified samples at 60kHz and the other using liquid metal at 50Hz, giving comparable result

Preparation and Characterization of Spherical Nickel Silicide Powder by Inductively Coupled Plasma Spheroidization for Additive Manufacturing

Author's accepted manuscriptMetal alloy powder with spherical-shaped morphology, high flowability, and packing density is the main requirements for metal-based additive manufacturing (AM). Among metal alloys, nickel silicide is considered as a potential candidate due to its unique properties such as high melting point, good electrical conductivity, as well as high corrosion and wear resistance. However, the fabrication of spherical nickel silicide powder has proven to be a challenging task. In the present work, spherical NiSi16 alloy powders were synthesized by inductively coupled plasma spheroidization (ICPS). The influence of the feed rate on the properties of the as-prepared powder was investigated using different analytical techniques to evaluate the particle morphology, particle size distribution, oxygen content, bulk density, fluidity, and spheroidization rate. The results showed some unique advantages of the ICPS technology in the preparation of spherical nickel silicide powder that is believed to be well suited for AM.acceptedVersio

Effect of (5%) CO2 on the Oxidation Rate During Cooling of Industrial Aluminum White Dross

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Tensile properties of Zr70Ni16Cu6Al8 BMG at room and cryogenic temperatures

The mechanical behaviour in tension of a hypoeutectic Zr70Ni16Cu6Al8 Bulk Metallic Glass (BMG) was studied at room (295 K) and cryogenic temperatures (150 K and 77 K) using various strain rates between 10−4 and 10−1 s−1. The yield strength was found to increase at lower temperatures with average values increasing by 16%, from 1503 MPa at 295 K to 1746 MPa at 77 K. The Zr-based BMG was found to exhibit tensile plastic elongation of about 0.4% before fracture at room temperature and high strain rates (10−1 s−1). Even higher tensile plasticity was recorded at low temperatures; plastic deformation was found highest at the intermediate temperature (150 K) reaching remarkable plastic strains in the order of 3.9%, while values up to 1.5% were recorded at 77 K. The lateral surface of the tensile specimens was observed in-situ during deformation using a high frame rate camera offering interesting insights with regard to the deformation mechanisms. Room temperature plasticity occurred through the formation and interaction of several nucleated shear bands before critical failure, while at intermediate and liquid nitrogen temperatures, most of the plastic deformation was accommodated through stable flow within a single shear band

Probing heat generation during tensile plastic deformation of a bulk metallic glass at cryogenic temperature

Despite significant research efforts, the deformation and failure mechanisms of metallic glasses remain not well understood. In the absence of periodic structure, these materials typically deform in highly localized, thin shear bands at ambient and low temperatures. This process usually leads to an abrupt fracture, hindering their wider use in structural applications. The dynamics and temperature effects on the formation and operation of those shear bands have been the focus of long-standing debate. Here, we use a new experimental approach based on localized boiling of liquid nitrogen by the heat generated in the shear bands to monitor the tensile plastic deformation of a bulk metallic glass submerged in a cryogenic bath. With the “nitrogen bubbles heat sensor”, we could capture the heat dissipation along the primary shear banding plane and follow the dynamics of the shear band operation. The observation of nitrogen boiling on the surface of the deforming metallic glass gives direct evidence of temperature increase in the shear bands, even at cryogenic temperatures. An acceleration in bubble nucleation towards the end of the apparent plastic deformation suggests a change from steady-state to runaway shear and premonitions the fracture, allowing us to resolve the sequence of deformation and failure events

Parametric optimisation of friction stir welding on aluminium alloy (EN AW-1100) plates

Friction stir welding is a solid-state welding process used extensively for aluminium alloys. EN AW-1100 alloy is mostly used for its exceptional corrosion resistance, high ductility, high thermal and electrical conductivities, and cost-effectiveness. This study is focused on the optimisation of friction stir welding parameters to achieve enhanced mechanical properties of 5mm thick EN AW-1100 alloy plates welded with a single pass, using Taguchi L9 orthogonal array and ANOVA analysis. Experimental results revealed that maximum tensile strength of 79 MPa and percentage elongation of 38.87 % were achieved. The maximum Vickers hardness achieved in the stir zone was 34.15. These results were used for optimisation using Minitab and it was determined that 2000 RPM, 30 mm·min−1 traverse speed and square probe profile came out to be the best parameters for maximum tensile strength. 4000 RPM, 30 mm·min−1 traverse speed and square probe geometry were the best parameters for maximum hardness in the stir zone. ANOVA analysis showed that the most significant parameter for tensile strength was traverse speed. None of the considered parameters were influencing the hardness value in the stir zone at a 95 % confidence level

Respiratory dysfunction three months after severe COVID-19 is associated with gut microbiota alterations

Background: Although coronavirus disease 2019 (COVID-19) is primarily a respiratory infection, mounting evidence suggests that the gastrointestinal (GI) tract is involved in the disease, with gut barrier dysfunction and gut microbiota alterations being related to disease severity. Whether these alterations persist and are related to long-term respiratory dysfunction remains unknown. Methods: Plasma was collected during hospital admission and after three months from the NOR-Solidarity trial (n = 181) and analysed for markers of gut barrier dysfunction and inflammation. At the three-month follow-up, pulmonary function was assessed by measuring the diffusing capacity of the lungs for carbon monoxide (DLCO ). Rectal swabs for gut microbiota analyses were collected (n = 97) and analysed by sequencing the 16S rRNA gene. Results: Gut microbiota diversity was reduced in COVID-19 patients with respiratory dysfunction, defined as DLCO below the lower limit of normal three months after hospitalisation. These patients also had an altered global gut microbiota composition, with reduced relative abundance of 20 bacterial taxa and increased abundance of five taxa, including Veillonella, potentially linked to fibrosis. During hospitalisation, increased plasma levels of lipopolysaccharide-binding protein (LBP) were strongly associated with respiratory failure, defined as pO2 /fiO2 -(P/F ratio)Respiratory dysfunction three months after severe COVID-19 is associated with gut microbiota alterationsacceptedVersio