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The article represents a multidisciplinary numerical model for electromagnetic casting of aluminum ingots, as well as the results of its application when casting aluminum ingots diam. 25–30 mm. The numerical model is based on a calculation of the electromagnetic field by solving an additional equation in Fluent combined with the modeling of processes connected with free surface crystallization. The obtained electromagnetic field sources are used in motion and energy equations for solving the magneto-hydrodynamics problem. A solution to the problem of determining the set of technological parameters for ensuring the stable formation of an ingot with the required diameter is provided along with the results of emergency mode modeling. In addition, the article presents the results of applying the established emergency modes at the laboratory casting unit with the electromagnetic mold for the production of ingots using Nikolin and Altsimak experimental alloys as part of ElmaCast® technology. [ABSTRACT FROM AUTHOR]

The application of the electromagnetic casting (EMC) to aluminum alloys is capable of producing structures, hardly obtainable by the conventional methods of casting due to the constant stirring of the crystallizing alloy and high cooling rate (∼103 K/s). For the first time we study EMC high purity binary Al-0.5Fe and Al-2.5Fe (wt.%) alloys in the as-cast state as well as after equal-channel angular pressing (ECAP) and cold rolling (CR). We demonstrate that EMC process leads to formation of metastable Al2Fe-alike intermetallic phase which does not decompose by further straining and annealing. Combined deformation by ECAP and CR results in the formation of ultrafine grained structure in which providing the increase in ultimate tensile strength up to 200 MPa in Al-0.5Fe and up to 340 MPa in Al-2.5Fe. Electrical conductivity level of Al-0.5Fe alloy increases up to 58.5% IACS, while the conductivity of Al-2.5Fe alloy decreases to 47.9% IACS. Both alloys demonstrate thermal stability of microstructure, mechanical and electrical properties under annealing up to 230 °C for 1h. These effects are discussed in terms of as-cast and strain-induced microstructures.

Aluminum alloys are one of the most common structural materials. To improve the mechanical properties, an alloy of the Al–Zn–Mg–Ca–Fe system was proposed. In this alloy, when Fe and Ca are added, compact particles of the Al10CaFe2 compound are formed, which significantly reduces the negative effect of Fe on the mechanical properties. Because of the high solidification rate (about 600 K/s) during cylindrical ingot (~33 mm) production, the electromagnetic casting method (ECM) makes it possible to obtain a highly dispersed structure in the cast state. The size of the dendritic cell is ~7 μm, while the entire amount of Fe is bound into eutectic inclusions of the Al10CaFe2 phase with an average size of less than 3 μm. In this study, the effect of radial shear rolling (RSR) on the formation of the structure and hardening of the Al–8%Zn–3.3%Mg–0.8%Ca–1.1%Fe alloy obtained by EMC was studied. Computer simulation of the RSR process made it possible to analyze the temperature and stress–strain state of the alloy and to select the optimal rolling modes. It was shown that the flow features during RSR and the severe shear strains near the surface of the rod (10 mm) provided a refining and decrease in the size of the initial Fe-containing particles. [ABSTRACT FROM AUTHOR]

The application of the electromagnetic casting (EMC) to aluminum alloys is capable of producing structures, hardly obtainable by the conventional methods of casting due to the constant stirring of the crystallizing alloy and high cooling rate (~10³ K/s). For the first time we study EMC high purity binary Al-0.5Fe and Al-2.5Fe (wt.%) alloys in the as-cast state as well as after equal-channel angular pressing (ECAP) and cold rolling (CR). We demonstrate that EMC process leads to formation of metastable Al2Fe-alike intermetallic phase which does not decompose by further straining and annealing. Combined deformation by ECAP and CR results in the formation of ultrafine grained structure in which providing the increase in ultimate tensile strength up to 200 MPa in Al-0.5Fe and up to 340 MPa in Al-2.5Fe. Electrical conductivity level of Al-0.5Fe alloy increases up to 58.5% IACS, while the conductivity of Al-2.5Fe alloy decreases to 47.9% IACS. Both alloys demonstrate thermal stability of microstructure, mechanical and electrical properties under annealing up to 230 °C for 1h. These effects are discussed in terms of as-cast and strain-induced microstructures. [ABSTRACT FROM AUTHOR]

In this work, an Al70Zn10Mg10Cu5Si5 medium entropy alloy was for the first time prepared by electromagnetic stirring casting. Electromagnetic casting has little effect on the generated phases in the as-cast alloys, and these phases are mainly composed of the α-Al solid solution, Mg2Si phase, Al2Cu phase, and MgZn2 phase. However, the electromagnetic frequency significantly affects the second phase's content, distribution, and morphology, especially for the Mg2Si phase, whose average particle size decreases from 40.0 to 17.7 μm. In addition, the compression mechanical properties were tested at room temperature, and it was found that the hardness, strength, and plasticity were effectively improved by applying a specific electromagnetic frequency. The optimal electromagnetic frequency was 20Hz in this work, under which the corresponding Vickers hardness, ultimate compressive strength δbc, and compressive yield strength δsc were 177 HV, 554 MPa, and 500 MPa, respectively. Moreover, mechanisms on the enhanced mechanical properties for the alloy fabricated with a proper electromagnetic frequency were systematically discussed. This first exploratory study can provide a reference for preparing Al-based medium entropy alloys by electromagnetic stirring casting.

In this work, a thermally stable model Al–4Cu–3Mn (wt%) alloy has been manufactured by electromagnetic casting (EMC), followed by compression, intermediate heat treatment and high-pressure torsion (HPT). Structural changes of the alloy during subsequent processing stages have been analysed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and the X-ray diffraction (XRD). The results indicate that variations in the intermediate heat treatment temperature of the compressed samples lead to a significant difference in strain hardening and thermal stability after HPT. According to microstructure investigations the hardening of samples processed by HPT resulted from formation of mixture of grains and subgrains with high dislocation density as well as mechanical fragmentation of eutectic Al 2 Cu particles and precipitation of nanoscale Mn-rich dispersoids which are identified as Al 6 Mn. The intermediate heat treatment of the EMC rod at 350 ºC for 3 hours and heat treatment of HPT sample at 250 ºC for 5 hours exhibited the best mechanical properties in terms of ultimate tensile strength (UTS), yield strength (YS) and elongation (El), reaching 610 MPa, 560 MPa and 10 % respectively. At the same time intermediate annealing at 450 °C makes the HPT processing ineffective. • A new thermally stable Al–4Cu–3Mn alloy was manufactured by electromagnetic casting and HPT. • The 350ºC-intermediate annealing combined with 250ºC-annealing after HPT exhibited the best mechanical properties. • The 450°C-intermediate annealing makes the HPT processing ineffective. • The alloy has better thermal stability up to 250ºC. [ABSTRACT FROM AUTHOR]

The article presents the results of obtaining an aluminum electrical wire with a diameter of 0.5 mm from alloys of the AleZr-Hf system used in aircraft. Alloys of three compositions were cast in the form of a billet with a diameter of 12 mm using the method of electromagnetic crystallization. Next, the rheological characteristics of billets from experimental alloys were studied. The obtained data were used to simulate the process of combined rolling-extrusion when obtaining a rod with a diameter of 5 mm from a billet with a diameter of 12 mm using the Deform 3D program. A comparison of the experimental forces and forces during the simulation is made for the forces acting on the rolls and the die of the CRE- 200 unit. At the next stage, experimental studies were carried out to obtain rods based on simulation data. The obtained rods with a diameter of 5 mm were subjected to drawing or sectional rolling with drawing and intermediate annealing to obtain a wire with a diameter of 0.5 mm. At all stages, the mechanical (ultimate tensile strength, yield strength, elongation to failure and area reduction) and electrophysical properties (electrical resistivity) of the obtained deformed semi-finished products were studied. [ABSTRACT FROM AUTHOR]

Aluminum alloys are one of the most common structural materials. To improve the mechanical properties, an alloy of the Al–Zn–Mg–Ca–Fe system was proposed. In this alloy, when Fe and Ca are added, compact particles of the Al10CaFe2 compound are formed, which significantly reduces the negative effect of Fe on the mechanical properties. Because of the high solidification rate (about 600 K/s) during cylindrical ingot (~33 mm) production, the electromagnetic casting method (ECM) makes it possible to obtain a highly dispersed structure in the cast state. The size of the dendritic cell is ~7 μm, while the entire amount of Fe is bound into eutectic inclusions of the Al10CaFe2 phase with an average size of less than 3 μm. In this study, the effect of radial shear rolling (RSR) on the formation of the structure and hardening of the Al–8%Zn–3.3%Mg–0.8%Ca–1.1%Fe alloy obtained by EMC was studied. Computer simulation of the RSR process made it possible to analyze the temperature and stress–strain state of the alloy and to select the optimal rolling modes. It was shown that the flow features during RSR and the severe shear strains near the surface of the rod (10 mm) provided a refining and decrease in the size of the initial Fe-containing particles.

A new method based on topology optimization is proposed for solving a three-dimensional axisymmetric inverse problem regarding the configuration of electric currents used in the electromagnetic casting technique of the metallurgical industry. These electric currents must generate an electromagnetic field such that when certain mass of liquid metal is placed in the field it levitates acquiring a predefined axisymmetric shape. The method proposed is able to obtain a suitable configuration of electric currents, and is very attractive from the computational point of view, since it is based on a sparse convex quadratic programming formulation for which there are very efficient interior-point solution algorithms. [ABSTRACT FROM AUTHOR]

The method of electromagnetic casting (EMC) was used to produce the long-length rod billet (with a diameter 12 mm) of aluminum alloy containing 0.6 wt.% Zr, 0.4%Fe, and 0.4%Si. The combination of high cooling rate (≈104 K/s) during alloy solidification and high temperature before casting (≈830 °C) caused zirconium to dissolve almost completely in the aluminum solid solution (Al). Additions of iron and silicon were completed in the uniformly distributed eutectic Al8Fe2Si phase particles with an average size of less than 1 µm. Such fine microstructure of the experimental alloy in as-cast state provides excellent deformability during wire production using direct cold drawing of EMC rod (94% reduction). TEM study of structure evolution in the as-drawn 3 mm wire revealed the onset of Al3Zr (L12) nanoparticle formation at 300 °C and almost-complete decomposition of (Al) at 400 °C. The distribution of Zr-containing nanoparticles is quite homogeneous, with their average size not exceeding 10 nm. Experimental wire alloy had the ultimate tensile strength (UTS) and electrical conductivity (EC) (234 MPa and 55.6 IACS, respectively) meeting the AT2 type specification. At the same time, the maximum heating temperature was much higher (400 versus 230 °C) and meets the AT4 type specification.

It is well known that radar absorbing potentiality of existing magneto-dielectric composites can be significantly enhanced by the application of frequency selective surface (FSS) and cascaded electromagnetic (EM) structures. But the optimization of such complex EM structures and validation of the adopted optimization strategy is still a very challenging task for the researchers. Therefore, in this study, an effective effort has been made for the optimization and the corresponding validation for Single Square FSS (SS-FSS) impinged and cascaded radar wave absorbers using advanced computational EM software’s like FEldberechnung fur Korper mit beliebiger Oberflache - a German acronym (FEKO) and high frequency structure simulator (HFSS). In addition, a critical analysis of dielectric constant (ε′) has been carried out to select the best combination of composites for the development of efficient radar wave absorbers. A comparison between optimized and simulated results have been carried out to examine the effect of advanced EM approaches over reflection loss (RL) characteristics of composite radar absorbing materials (CRAMs). A rapid change in radar absorption properties of composites has been observed after the application of SSFSS and cascading. A SS-FSS impinged composite has been found to provide a wide absorption bandwidth of 3.6 GHz at X-band. A cascaded absorber having layer thickness 1.8 mm provides a peak RL of −42.6 dB at 10.6 GHz with an absorption bandwidth of 2.5 GHz. The strong agreement between mathematical model, HFSS and FEKO results clearly reflects the efficiency of adopted approach for distinct practical EM applications. [ABSTRACT FROM AUTHOR]

In this paper we deal with an inverse electromagnetic casting problem, which consists in designing a set of inductors in such a way that a liquid metal achieves a given shape. The inductors are assumed to be made of single solid-core wires with a negligible cross-section area. The inverse problem is rewritten in the form of an optimization problem. In particular, a Kohn-Vogelius based functional is minimized with respect to a set of admissible inductors, leading to a non-iterative second order optimization algorithm. Finally, several numerical examples are presented showing that the proposed approach is effective to design suitable inductors. [ABSTRACT FROM AUTHOR]

It is a challenge to detect the weld position during tight butt joint laser welding in that the tight butt joint is non-grooved and invisible. This paper proposes a novel method for tight butt joint weld detection based on magneto optical imaging. Two pieces of weldment were magnetized by an electromagnet so that they could show magnetic N and S polarity respectively. When a polarized light was projected on a magneto-optical film, it would deflect due to magneto-optical effect. In accordance with magneto field distribution, an image formed on the visual sensor. A transition zone of magnetic field distribution which corresponded to the butt joint could be shown in a magneto optical image of weldment. Variation features of magnetic field distribution were obtained by using image sequence optical flow method, and a particle filter was integrated to make an accurate prediction on weld position. Weld position was obtained by calculating the maximum value of optical flow intensity in the vertical direction, and a particle filter was used to realize the accurate prediction on weld position. Experimental results showed that the proposed method was effective in detection of weld and realizing weld seam tracking. [ABSTRACT FROM AUTHOR]

A novel printed rectangular slotted patch antenna with defected Ground plane(DGS) for dual-band operations is presented. By embedding a T-shaped strips and defecting L-shaped slot in the ground plane, triple-mode resonances for achieving dual operations bands can be excited for achieving additional resonances. The designed antenna has very small size of 15 x 20 x 0.8mm3 printed on FR4 substrate and operate over the frequency ranges, (3.2-3.6) GHz and (5.02-6.64) GHz suitable for WiMAX (3.5/5.5GHz),WLAN (5.2/5.8GHz) and ISM medical band (5.725-5.82GHz). Simulation results show that the antenna gives an acceptable gain over the operating bands. In addition, effects dimensions of the T-shaped strips and the DGS for this design on the electromagnetic performance are examined and discussed in detail. The antenna was simulated using Computer Simulation Technology Microwave Studio (CST MWS) based on the finite difference time domain (FDTD). Finally, the proposed antenna was fabricated and reflection coefficient parameter was measured to validate against simulation results. [ABSTRACT FROM AUTHOR]

The graphene/CoFeO/YFeO nanocomposite were successfully synthesized by a deoxidation technique. The phase composition, morphology and electromagnetic properties of the composites were characterized by X-ray diffractometer, scanning electron microscope, X-ray photoelectron spectroscopy, Raman spectra, and vector network analyzer. The electromagnetic parameters of the graphene/CoFeO/YFeO nanocomposite were investigated in the 2-18 GHz range. The experimental results show that the graphene/CoFeO/YFeO nanocomposite exhibits evidently enhanced microwave absorbing performance in comparison with the CoFeO/YFeO nanocomposite. An effective absorption band is obtained by graphene/CoFeO/YFeO nanocomposite at 14-16 GHz and the maximum reflection loss is −36.1 dB at 14.88 GHz. [ABSTRACT FROM AUTHOR]

The effect of electromagnetically induced transparency (EIT) has been experimentally implemented for the first time for the (4 S -4 P -4 S ) Λ-system of potassium atom levels in a nanocell with a 770-nm-thick column of atomic vapor. It is shown that, at such a small thickness of the vapor column, the EIT resonance can be observed only when the coupling-laser frequency is in exact resonance with the frequency of the corresponding atomic transition. The EIT resonance disappears even if the coupling-laser frequency differs slightly (by ~50 MHz) from that of the corresponding atomic transition, which is due to the high thermal velocity of K atoms. The EIT resonance and related velocity selective optical pumping resonances caused by optical pumping (formed by the coupling) can be simultaneously recorded because of the small (~462 MHz) hyperfine splitting of the lower 4 S level. [ABSTRACT FROM AUTHOR]

In the present work, A356/SiC Metal Matrix Composite (MMC) with different weight percent of SiC particles were fabricated by two different techniques, such as Mechanical stir-casting and Electromagnetic stir casting. The wear and frictional properties of the metal matrix composites were studied by performing dry sliding wear test using a pin-on-disc wear tester for both electromagnetic stir casting samples and mechanical stir casting samples. The wear rate increases with the addition of normal force, while decreases when the percentage of reinforcement is increased. Frictional coefficient increases by increasing the normal force and percentage of reinforcement. By increasing percentage of reinforcement and using electromagnetic stir casting process, the higher frictional coefficient and lower wear rate are obtained. [ABSTRACT FROM AUTHOR]

The effects of different Fe contents (0.168, 0.356 and 0.601 wt%) on microstructures and mechanical properties of the Al–1.6Mg–1.2Si–1.1Cu–0.15Cr–0.15Zr (all in wt%) alloys prepared by low frequency electromagnetic casting process were investigated in the process of solidification, hot extrusion, solid solution and aging treatments. The results show that the increase of Fe content promotes the formation of feathery grains in the process of solidification and the precipitation of another important strengthening phase Q′ with small size. Additionally, it also results in no recrystallization even after solid solution at a high temperature of 550 °C, which is because of the increase number of elliptical shaped and fine DO22-Al3Zr dispersoids (∼70 nm long and ∼35 nm wide) and the spherical or elliptical shaped Fe-containing phases. When Fe content of the alloy increases to 0.356 wt%, both the ultimate tensile strength and yield strength of the alloy-T6 increase by more than 60 MPa and with little cost of ductility. [ABSTRACT FROM PUBLISHER]

Slurry preparation is one of the most critical steps for semisolid casting, and its primary goal is to prepare slurry with uniformly distributed fine globules. In this work, electromagnetic stirring (EMS) and the addition of Sc and Zr elements were used to prepare semisolid slurry of 7A04 aluminum alloy in a large diameter slurry maker. The effects of different treatments on the microstructure, composition and their radial homogeneity were investigated. The results show that, compared to the slurry without any treatment, large volume slurry with finer and more uniform microstructure can be obtained when treated by EMS, Sc, or Zr additions individually. EMS is more competent in the microstructural and chemical homogenization of the slurry while Sc and Zr additions are more excellent in its microstructural refinement. The combined treatment of EMS, Sc and Zr produces premium 7A04 aluminum alloy slurry with uniformly distributed fine α-Al globules and composition. The interaction mechanism between EMS and Sc and Zr additions was also discussed. [ABSTRACT FROM AUTHOR]

The paper aims to clarify the effects of electromagnetic frequency on magnesium alloy AZ80 billets during low frequency electromagnetic casting. It proposes a mathematic model, verified against the temperature measurements obtained from AZ80 alloy billet of 160 mm in diameter, to predict the interaction of electromagnetic field, fluid flow, and temperature distribution. The sump depth becomes deeper and the maximum sustained speed of melt flow increases with the increase of electromagnetic frequency. By the analysis of the effects of fluid flow and temperature field on the solidification in the presence of electromagnetic field, the best electromagnetic parameters are given. [ABSTRACT FROM AUTHOR]

In the present work, the strength and distribution of electromagnetic field in the square cold crucible that designed for casting multicrystalline silicon were measured and analyzed by using a small coil method. The results show that in the perpendicular direction the maximum of magnetic flux density (B) appears at the position slightly above the middle of the coil, and then B attenuates toward both sides, and decreases more to the bottom of the crucible. In the horizontal direction, from the edge (corner) to the center, B firstly decreases gradually, and then slightly increases in the center. While along the inner sides of the crucible, the distribution is relatively uniform, especially in the effective acting range. B increases with the increasing of the input power. Moving the coil to the top of the crucible, B increases and the effective acting range of the electromagnetic field becomes bigger. For the coils with different turns, the five turns coil can induce the highest magnetic flux density.

The parameters and factors that influence the surface quality and macrostructure of titanium alloy with reactive properties under liquid state were studied experimentally using a cold crucible electromagnetic casting method. The variations in the process parameters have great impact on the surface quality and macrostructure of cast billets. Billets with crack free and smooth surfaces as well as directional solidified primary structures were obtained after the selection of optimized process parameters. The formation mechanisms of defects such as cracks and non-directional structural morphology were interpreted briefly. Finally, the casting of billets with good outer qualities and inner column grains has been attained successfully, which in turn gives a solid foundation for further development of the technology.

In the present research, microstructure refinement of a high-Nb TiAl alloy (Ti-48Al-8Nb-0.15B) was realized by means of the electromagnetic continuous casting (EMCC) technique. The microstructure of an ingot obtained by EMCC was analyzed using scanning electron microscopy (SEM). As compared with the raw as-cast alloy, the obtained EMCC alloy presented a much finer microstructure with lamellar colonies with a mean size of about 50-70 µm because the electromagnetic stirring broke initial dendrites and enhanced the heterogeneous nucleation. As the grains were refined, the properties of the TiAl alloy were improved significantly. This implies that the EMCC technique could offer the possibility of application for high-Nb TiAl alloys with a refined microstructure and excellent properties to be used as a structural material. [ABSTRACT FROM AUTHOR]

Woven carbon fibers reinforced Al–Mg (95–5 wt%) matrix composites were successfully prepared by an electromagnetic casting method. In order to improve the wetting behavior, different stabilizers were respectively used in the electroless plating process to coat the fibers with a better Ni/P layer. The lactic acid offered the most outstanding stabilizing effect. The casting results indicated that the contact time between the molten metal and the carbon fibers was vital to the bonding degree: increasing the solidification time significantly reduced the cavity defects which located near the interface; however, an overly long solidification time would result in a tendency to crack in the centers of the woven fibers. The hot-pressing treatment with optimum parameters significantly mitigated the crack and cavity defects which are common in the composite prepared through casting method. The appropriate applied compression ratio turned out to be approximately 6%. Three point bending test showed that the bending strength of the composite had an improvement for 33.6% than that of Al-alloy matrix. [ABSTRACT FROM AUTHOR]

Woven carbon fibers reinforced Al–Mg (95–5 wt%) matrix composites are successfully prepared through an electromagnetic casting process. The Ni/P coating is obtained using an electroless plating method to offer a better wettability in the casting. The appropriate pre-heating temperature of reinforcement is determined to be 600 K, and the molten matrix temperature should be controlled at approximately, 1013 K. Due to the presence of Ni/P coating, the infiltrated metal is able to spread out on the fiber surface readily. Finally, the accumulation of the metal on the fibers eventually fills all interspaces in the woven fibers. The addition of Mg shows a beneficial effect during the casting process by transferring itself into the coating more readily than Al and by segregating closely around the fibers, which effectively limits the formation of the Al 4 C 3 brittle phase. The mixing enthalpy theory is introduced to explain the distribution of elements in this composite. [ABSTRACT FROM AUTHOR]

Purpose: Electromagnetically guided endoscopic procedure, which aims at accurately and robustly localizing the endoscope, involves multimodal sensory information during interventions. However, it still remains challenging in how to integrate these information for precise and stable endoscopic guidance. To tackle such a challenge, this paper proposes a new framework on the basis of an enhanced particle swarm optimization method to effectively fuse these information for accurate and continuous endoscope localization. Methods: The authors use the particle swarm optimization method, which is one of stochastic evolutionary computation algorithms, to effectively fuse the multimodal information including preoperative information (i.e., computed tomography images) as a frame of reference, endoscopic camera videos, and positional sensor measurements (i.e., electromagnetic sensor outputs). Since the evolutionary computation method usually limits its possible premature convergence and evolutionary factors, the authors introduce the current (endoscopic camera and electromagnetic sensor's) observation to boost the particle swarm optimization and also adaptively update evolutionary parameters in accordance with spatial constraints and the current observation, resulting in advantageous performance in the enhanced algorithm. Results: The experimental results demonstrate that the authors' proposed method provides a more accurate and robust endoscopic guidance framework than state-of-the-art methods. The average guidance accuracy of the authors' framework was about 3.0 mm and 5.6° while the previous methods show at least 3.9 mm and 7.0°. The average position and orientation smoothness of their method was 1.0 mm and 1.6°, which is significantly better than the other methods at least with (2.0 mm and 2.6°). Additionally, the average visual quality of the endoscopic guidance was improved to 0.29. Conclusions: A robust electromagnetically guided endoscopy framework was proposed on the basis of an enhanced particle swarm optimization method with using the current observation information and adaptive evolutionary factors. The authors proposed framework greatly reduced the guidance errors from (4.3, 7.8) to (3.0 mm, 5.6°), compared to state-of-the-art methods. [ABSTRACT FROM AUTHOR]

An AZ80 alloy containing 1 wt% Ca (1 wt% Ca-AZ80 alloy) was fabricated using a combination of electromagnetic casting and electromagnetic stirring. Due to the beneficial effects of reduction in the temperature gradient in the melt and refinement of dendritic structure by enhanced fluid motion, the fine and homogeneous microstructure could be obtained in the billets. Compression tests were performed on the cast 1 wt% Ca-AZ80 alloy to examine its hot deformation behavior in the temperature range of 523–693 K and the strain rate range of 10 −3 –10 1 s −1 . The analysis of the deformation behavior indicated that the lattice diffusion controlled Garofalo׳s hyperbolic sine creep with stress exponents of 6–7 dictates the plastic flow at the given testing conditions. The size of the dynamically recrystallized (DRX) grains and the volume fraction of the DRX grains decreased as the Zener–Hollomon parameter increased. A comparison of the processing maps of the cast 1 wt% Ca-AZ80 alloy with those of the conventionally processed cast AZ80 alloy studied by other investigators at strains of 0.2–0.5 indicated that the former exhibits a better hot workability over a wider range of temperatures and strain rates. This may be attributed to the microstructural refinement and homogeneity of the present alloy achieved by a combination of EMC and EMS, which is superior to those of the magnesium alloys obtained by conventional casting process, and the additional presence of thermally stable Al 2 Ca phase in the 1 wt% Ca-AZ80 alloy. [ABSTRACT FROM AUTHOR]

Abstract: In this study the effect of twin-roll casting (TRC) producing conditions on microstructure and mechanical properties of Al-7075 alloys has been investigated in detail. When introducing an electric pulse (EP) of 400I peak current and 30Hz into the conventional TRC process, the dendrites are refined and equiaxed accompanied by thick segregation bands beingabated. The most uniform structure of 7075 alloy is obtained after applying a static magnetic field of 0.2T at the same time. EDS spectrum analysis shows that the netlike T (AlZnMgCu) phase is resolved while the mixture of η (MgZn2) and CuMg2 phases improves. Moreover the increase in solute diffusivity is due to the modification of heat and mass convections by the incoming EP energy, facilitating the realization of excellent mechanical properties. The tensile tests reveal that the optimum process, in which the highest strength and ductile manner were obtained, is considered to be EP electromagnetic TRC modification. [Copyright &y& Elsevier]

Abstract: The Al 1.6Mg 1.2Si 1.1Cu 0.15Cr (all in wt. %) alloys with and without Zr addition prepared by low frequency electromagnetic casting process were investigated by using the optical microscope, scanning electron microscope and transmission electron microscope equipped with energy dispersive analytical X-ray. The effects of Al3Zr phases on the microstructures and mechanical properties during solidification, homogenization, hot extrusion and solid solution were studied. The results show that Al3Zr phases reduce the grain size by ~29% and promote the formation of an equiaxed grain structure during solidification. Numerous spherical Al3Zr dispersoids with 35–60nm in diameters precipitate during homogenization, and these fine dispersoids change little during subsequent hot extrusion and solid solution. Adding 0.15wt. % Zr results in no recrystallization after hot extrusion and partial recrystallization after solid solution, while the recrystallized grain size is 400–550μm in extrusion direction in the Zr-free alloy. In addition, adding 0.15wt. % Zr can obviously promote Q′ phase precipitation, while the β″ phases are predominant in the alloy without Zr. Adding 0.15wt. % Zr, the ultimate tensile strength of the T6 treated alloy increases by 45MPa, while the elongation remains about 16.7%. [Copyright &y& Elsevier]

A new optimization method is proposed for solving an inverse problem concerning the shape and topology of the inductors used in the electromagnetic casting technique of the metallurgical industry. The method is based on an sparse convex quadratic programming version of a recently proposed topology optimization formulation of the inverse electromagnetic casting problem. Regular 0–1 solutions are found by adding to the original Kohn–Vogelius objective function an appropriate penalty term that preserves the quadratic programming structure of the problem, allowing the use of efficient interior-point algorithms. Results for some numerical examples are presented, showing that the technique proposed is effective and can successfully find inductors of optimal shape and topology. [ABSTRACT FROM AUTHOR]

This article proposes a novel separable field shaper design for electromagnetic sheet impact forming. The efficiency of the field shaper under different geometric parameters was evaluated through a combination of the Taguchi method and three-dimensional coupled simulation. The deviation in impact velocity between the experiment and the simulation was under 3%. The results indicate that the slit feature determines the performance of the field shaper. Wider slits reduce the energy loss resulting from electromagnetic repulsion. In addition, with more field shaper components, the generated magnetic pressure will be distributed more evenly. Based on the analysis result of the nonsymmetric edge effect, some guidelines for designing the field shaper are proposed. [ABSTRACT FROM AUTHOR]

In this article we present an algorithm for inverse optimization problems concerning electromagnetic casting of molten metals. We are interested in locating suitable inductors around the molten metal so that the equilibrium shape will be as near as possible to a desired target shape. A simultaneous analysis and design mathematical programming formulation is stated for the inverse problem. The resulting optimization problem is solved with FAIPA, a feasible directions interior-point algorithm. [ABSTRACT FROM AUTHOR]

In this work, we study the direct and inverse problems arising from electromagnetic shaping in applications such as continuous casting processes. The magnetic field produces a surface pressure which forces a molten metal to change its shape until it reaches an equilibrium state between the magnetic pressure and the surface tension. The arising direct problem is a free boundary problem which is to determine the shape of molten metals for a given magnetic field. On the other hand, the inverse problem is to seek a configuration of electromagnetic field generators (i.e. inductors) in order that molten metals have prescribed shapes. A level set method will be presented to determine an equilibrium shape formed by a given configuration of magnetic fields. Also a computational method as well as uniqueness results for the inverse problem will be introduced and illustrated with examples. [ABSTRACT FROM AUTHOR]

Abstract: Electromagnetic casting is a novel technology that combines the advantages of electromagnetic cold crucible and continuous casting. By controlling induction heating and strengthening bottom cooling, multicrystalline silicon ingot with 60mm×60mm in cross section was continuously and directionally solidified by this technology. The ingot shows smooth surface and consists of uniform columnar crystals with no precipitate except in the top part. The grain size of the top part is smaller due to higher impurity content and the impurities acting as nucleation sites for grain. The density of dislocations at the bottom and middle parts, about 1×106 cm−2, is much less than that at the top part. [Copyright &y& Elsevier]

Abstract: The inverse electromagnetic casting problem consists in looking for a suitable set of electric wires such that the electromagnetic field induced by an alternating current passing through them makes a given mass of liquid metal acquire a predefined shape. In this paper we propose a new method for the topology design of such inductors. The inverse electromagnetic casting problem is formulated as an optimization problem, and topological derivatives are considered in order to locate new wires in the right position. Several numerical examples are presented showing that the proposed technique is effective to design suitable inductors. [Copyright &y& Elsevier]