Search

In the general smelting process, nonmetallic compounds manifest as inclusions. These inclusions, typically larger than 5 μm, can significantly reduce the strength, toughness, and processability of steel. More critically, they pose a threat to the service life of steel. To mitigate these adverse effects, the practice of inclusion modification has been developed. Typically, calcium and magnesium elements are employed for this purpose. However, despite these efforts, the size of modified inclusions often remains at the micron level. Although there is some improvement in mechanical properties, the presence of these inclusions still compromises the steel matrix. Therefore, controlling the size, quantity, and distribution of nonmetallic inclusions during steel manufacturing becomes imperative. When inclusions are reduced to nanometer size, the formation of a high density of nanosized second-phase particles can substantially improve the strength and toughness of the steel. In this study, we prepared Fe–0.04C–1.5Mn–0.5Ti–0.5Al2O3 (Fe–TAMO) steel by applying a dynamic magnetic field during the smelting process. This was followed by grain size optimization and equiaxed optimization through rolling and annealing processes. Transmission electron microscopy revealed that the second-phase particles were uniformly dispersed within the as-cast Fe–TAMO steel matrix. The density of these particles reached 3.3 × 1015 m−2, with an average diameter of 2.75 ± 0.803 nm. Energy-dispersive x-ray spectroscopy analysis identified these particles as oxides of Ti–Al–Mn. The compressive mechanical properties of Fe–TAMO steel, in its as-cast, as-rolled, and as-annealed states, were evaluated using a universal testing machine. The grain size of the as-cast Fe–TAMO steel is 143 μm, with a compressive yield strength of 150 MPa, approximately double that of as-cast pure ferritic steel. After rolling, the grain size decreased to 119 μm, and the compressive yield strength increased to 484 MPa. Following annealing, the grain size was further reduced to 64 μm, with a compressive yield strength of 334 MPa. These results demonstrate that the applied method effectively minimizes the size of the second-phase particles, with most controlled within 5 nm. The densely distributed second-phase nanoparticles significantly improve the steel strength, while subsequent heat treatments allow for adjustments in grain size to further enhance mechanical properties. This method streamlines the process flow to a single step, achieving uniform dispersion of ultrafine nanosized second-phase particles in the steel matrix in about a mere 3 minutes. Moreover, it holds great potential for industrial production, offering a new avenue for the mass production of high-performance steel.

In this study, a systematic evaluation was conducted on the performance of Al 2 O 3 , MgO, BaZrO 3 and Y 2 O 3 crucibles for melting Zr-based bulk metallic glass master alloys. The interaction between the crucibles and the alloy melts was investigated, focusing on the effect of crucible type and the addition of Y element on the interaction. The results indicated that the relative stability of the evaluated oxide crucibles, in order of decreasing interaction extent, followed the sequence: MgO→Y 2 O 3 →Al 2 O 3 →BaZrO 3. The grading did not follow the free energy data of the formation of these oxides. It was because that the Y combined with O in the alloy melts to form Y 2 O 3 products, which adhered to the inner surface of the crucible. This further prevented the dissolution of the crucible refractory. Among the tested crucibles, the Y 2 O 3 product layer exhibited the most complete structure on the surface of BaZrO 3 crucible, thereby minimizing both the corrosion of the crucible and the contamination of the alloy melts. [ABSTRACT FROM AUTHOR]

In this work, 52Ti–12V–36Cr + 4 wt% Zr alloy was synthesized at laboratory and large scales for comparative analysis of the hydrogen storage performance. A 5 g and 2 kg BCC solid solution alloy is synthesized by arc melting and induction melting, respectively. Crystal structure investigation revealed that both samples crystallized into a primary BCC phase and a secondary laves phase with no significant difference in the overall XRD pattern. First hydrogenation studies showed the maximum hydrogen storage capacity of arc melted alloy (AM) and induction melted alloys (IM) alloy are 3.5 wt% and 2.9 wt%, respectively, at room temperature under a hydrogen pressure of 20 bar. No visible incubation period was observed in AM alloy, whereas IM alloy showed an incubation period of 32 min with slower kinetics. The appearance of the incubation period and sluggish kinetics can be due to the formation of a passive layer during induction melting that changes the hydrogen sorption properties. The microstructural analysis confirmed the carbon contamination from the induction melting crucible and formation of the TiC phase in the matrix, which was absent in the AM alloy, significantly affecting hydrogen storage capacity. The enthalpy and entropy of 2 kg alloy are −65.84 kJ/mol and 188.92 J/mol-K. [Display omitted] • 52Ti–12V–36Cr + 4 wt% Zr synthesized successfully on a large scale. • Comparison of samples from laboratory-scale arc melting and large-scale induction melting. • Hydrogen storage capacity for the arc melted sample is 3.5 wt%, and the induction melted sample is 2.9 wt%. • Microstructure shows the formation of the Ti–C phase in the induction melted sample. [ABSTRACT FROM AUTHOR]

Additive manufacturing is becoming increasingly widespread and has developed very dynamically in recent years. For the processing of metals, powder or wire is usually used as the feedstock. The energy source used in wire-based processes is usually electric arcs or lasers. In this contribution, a technological approach for additive manufacturing of metal structures by induction melting with pulsed generator power is used. Therefore, the principle of oscillating Lorentz forces is utilized in this approach and analytically investigated with the aid of a FE simulation model. In the experiments, a continuously fed steel wire is inductively melted and deposited dropwise onto a substrate heated to different preheating temperatures without the use of a nozzle or crucible. [ABSTRACT FROM AUTHOR]

Electromagnetic processing of molten copper is provided in a special kind of electrical furnace called an induction furnace with a cold crucible (IFCC), making it possible to successfully remove impurities from the workpiece. In order to analyze the process in a sufficient way not only electromagnetic, thermal and flow but also metallurgical and mass transfer phenomena in the coupled formulation should be taken into consideration. The paper points to an analysis of the kinetic process of lead evaporation from molten copper. It was shown that mass transport in the gas phase determines the rate of the analyzed evaporation process. The possibility of removal of lead from molten copper is analyzed and described.

The effects of vacuum induction melting and various concentrations (range of 0–8% by weight) of the titanium aluminium carbide (Ti2AlC) phase on the mechanical and tribological properties of Aluminium hypereutectic alloy (A390) were investigated. The addition of Ti2AlC particles enhances the strength and wear resistance of A390 alloy and also exerts a positive effect on its ductility, Moreover aerospace and automotive brake rotors deserved high strength and high wear resistance. The quick induction heating process could decrease the thermal energy degradation of the Ti2AlC particles into an Al alloy matrix alloy. The structural, microscopic and elemental analysis carried out to observe the hard precipitate components and reveal the various phases of the composites. The addition of Ti2AlC inclusions altered the morphology of eutectic silica to be globular and improved the grain size and evenly distributed within the A390 (Al-16Si) matrix. As the content of Ti2AlC reaches 8 wt% the strength and microhardness of the composites increased 74% and elongation decreased 2.1% (UTS = 285 MPa, H = 127VMH and EI = 1.1%). The tensile and fracture behaviour of the composites has been studied at 30 °C, 150 °C, and 250 °C. The Johnson-Cook model theoretically calculated the accurate flow stress of the Al-16Si/Ti2AlC composites. The negligible decrease in strength and ductility at 250 °C was observed. The root mean squared error (RMSE) and mean absolute percentage error (MAPE) values for the stress-strain curves prove the higher relationship between the theoretical and experimental values. The composites containing 8 wt% Ti2AlC reinforcement significantly enhanced the mechanical behaviour with a porosity < 2.23%.Therefore this composite exhibited appreciable tribological properties. It appeared that the wear mechanism of the composites abrasive wear at applied pressure 0.2 MPa with sliding distance 2000 m was prevailing. The ANN model addressing the parameters which influence the wear rate and friction coefficient as well as the experimental wear analysis of these composites was correlated precisely with the results of this model. [ABSTRACT FROM AUTHOR]

Ca–Ni systems have been regarded as poor cousins to La–Ni based systems for hydrogen storage, owing to their reduced absorption capacity. However, Ca–Ni based systems offer the particular benefit of rapid activation and reduced absorption pressure. The inclusion of copper as a substitutional element in the CaNi 2 –CaNi 3 two-phase alloy has been found to enhance the hydrogen absorption capacity. This enhancement is comparable to that observed in the LaNi 5 alloy, while also preserving or even improving upon other advantageous properties such as absorption pressure and activation characteristics. The results of the study indicate that the Ca–Ni–Cu alloy exhibits an absorption capacity of 1.4 wt% at a temperature of 25 °C and a pressure of ∼0.5 atm. The activation of the alloy occurs within three cycles under relatively mild conditions, specifically at a temperature of 25 °C and a pressure of 10 atm. The alloy demonstrates rapid kinetics, as evidenced by the absorption of 1.4 wt% of hydrogen within 50 s at 25 °C and a pressure of 10 atm. The current investigation emphasises a cost-effective and commercially viable hydrogen storage alloy, devoid of costly rare earth elements. • Cu substituted two phase alloy with CaNi 2 and CaNi 3 type phases is synthesised by vacuum induction melting route. • At 25 °C, the alloy absorbs 1.4 wt% hydrogen at 0.5 atm pressure and 1.5 wt% hydrogen at 3 atm. • The alloy also exhibits rapid kinetics of hydrogen absorption, with 1.41 wt% H uptake within 50 s at 25 °C and 10 atm. • 'Dual Metal Supported Catalytic System" forms on the surface enhancing absorption via 'hydrogen spillover'. • A cost-effective and commercially viable hydrogen storage alloy, devoid of costly rare earth elements. [ABSTRACT FROM AUTHOR]

In this study, we compare the thermoelectric properties of coarse-grained n-type Bi2Te2.55Se0.45 alloy prepared by induction melting with the bulk-nanostructured prepared by ball milling and hot-pressing techniques. The corresponding thermoelectric properties showed different behavior for each material processed using different routes. The most striking result of the study is observing a p-type behavior and charge carrier transition from p-to n-type for the coarse-grained alloy. These observed phenomena are related mainly to the unique needle-like microstructure accompanied by high lattice strain. Lastly, the obtained figure-of-merit values for the coarse needle-like structure and bulk nanostructured Bi2Te2.55Se0.45 alloys are 0.20 and 0.80 at their optimum temperatures of 60 and 120 °C, respectively.

Electromagnetic processing of molten copper is provided in a special kind of electrical furnace called an induction furnace with a cold crucible (IFCC), making it possible to successfully remove impurities from the workpiece. In order to analyze the process in a sufficient way not only electromagnetic, thermal and flow but also metallurgical and mass transfer phenomena in the coupled formulation should be taken into consideration. The paper points to an analysis of the kinetic process of lead evaporation from molten copper. It was shown that mass transport in the gas phase determines the rate of the analyzed evaporation process. The possibility of removal of lead from molten copper is analyzed and described. [ABSTRACT FROM AUTHOR]

Vacuum induction melting in a refractory crucible is an economical method to produce TiAl-based alloys, aiming to reduce the preparation cost. In this paper, a Sr2CeZrO6 refractory was synthesized by a solid-state reaction method using SrCO3, CeO2 and ZrO2 as raw materials, and its interaction with TiAl alloy melt was investigated. The results showed that a single-phase Sr2CeZrO6 refractory could be fabricated at 1400 °C for 12 h, and its space group was Pnma with a = 5.9742(3) Å, b = 8.3910(5) Å and c = 5.9069(5) Å. An interaction layer with a 40μm thickness and dense structure could be observed in Sr2CeZrO6 crucible after melting TiAl alloy. Additionally, the interaction mechanism showed that the Sr2CeZrO6 refractory dissolved in the alloy melt, resulting in the generation of Sr3Zr2O7, SrAl2O4 and CeO2−x, which attached to the surface of the crucible. [ABSTRACT FROM AUTHOR]

A new neutron multiplier based on lanthanum plumbide LaPb3 was produced using two different casting methods. The argon-arc melted material consists of LaPb3 dendrites between grains of LaPb2 phase of approximately equal volume fraction. The induction melted material is composed primarily of large LaPb3 grains, about 80 μm in size. Corrosion testing at 20 and 300 °C in air revealed the rapid degradation of LaPb3 without the formation of a protective passivation layer. The corrosion process results in significant volumetric expansion accompanied by cracking. When LaPb3 is exposed to air at 500 °C, pure lead as a corrosion product melts to form layers protecting against rapid corrosion. LaPb3 showed low (113–193 MPa), but sufficient strength for functional use in the temperature range of 20–500 °C.

Copper alloys are typically produced by conventional casting processes, as well as spark plasma sintering (SPS), which often produce inhomogeneous mixtures and unwanted intermetallic phases. This paper presents an induction melting technology, which should provide good mixing, controlled heating and melt stirring, potentially improving homogeneity. Homogeneous melts should produce homogeneous powders, with constant properties. This powder was spheroidized for increasing powder flow and particle packing for applications such as additive manufacturing (AM). A density test was developed to ascertain homogeneity of the solidified product to improve potential AM component quality. Al-33Cu, Al-50Cu and Al-67Cu (at.%) buttons were produced by high-frequency (HF) induction melting, to give better mixing and hence phase distributions. The phases and their distributions were studied using scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), x-ray diffraction (XRD) and absolute density using helium pycnometry. There was acceptable homogeneity found in the Al-33Cu sample, but not in Al-50Cu and Al-67Cu samples. This was attributed to Al loss (due to evaporation), complex solidification mechanisms and phase density segregation. [ABSTRACT FROM AUTHOR]

The specific features of a copper–nickel MN45-VP constantan alloy of vacuum melting are taken into account to reveal the possible causes of the appearance of characteristic hillocks on metallographic sections of its rods as a kind of surface whisker effect. The formation of hillocks is shown to be a consequence of diffusion processes induced by a high chemical heterogeneity of the material. This heterogeneity is found to be related to the absence of special electromagnetic devices in an induction melting furnace for mixing the melt, the components of which are separated in magnetic susceptibility. In other words, the time of holding the melt during cooling-down in the course of degassing is too short. [ABSTRACT FROM AUTHOR]

High-entropy alloys are emerging materials and are widely studied at the synthesis and characterization levels. Their machinability study and product realization are still at a nascent stage. Conventional machining operations are necessary to ensure part assembly and surface quality. Hence, end-mill machining is carried out to check the machinability of the most ductile equiatomic and non-equiatomic CrMnFeCoNi high-entropy alloy (HEA) with a green manufacturing concept. Theoretical and experimental analyses examined the effect of percent composition of an element in a high-entropy alloy and machining parameters (spindle speed, depth of cut and feed per tooth) on the cutting forces, chip morphology, machined surface topography, surface micro-hardness and tool wear mechanism. Kistler dynamometer installed in CNC vertical milling machine is used with AlTiN-coated tungsten carbide tool to record the cutting forces and moments. The microstructure anisotropy induced by low vacuum induction melting of varying compositions of elements in high-entropy alloys influenced the machining results. Feed force values were higher for the non-equiatomic HEA sample than for the equiatomic CrMnFeCoNi HEA. SEM and EDS mapping has revealed microhole and microcrack surfaces after machining. Equiatomic CrMnFeCoNi HEA has shown the highest microhardness of 984 Hv than the non-equiatomic HEA sample. [ABSTRACT FROM AUTHOR]

Copyright of BHM Berg- und Hüttenmännische Monatshefte is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper is concerned with the study of the processes of melting volcanic rock in a cold-crucible induction furnace in order to obtain a high melt bath and study its degassing. The results of experiments carried out to assess the thermal stability of the melt, determine its energy characteristics, and study the melt behavior at a current frequency of 5.28 MHz using a cold crucible with an inner diameter of 114 mm are presented. As a result of the study, a volcanic-rock melt bath 0.64 m high was obtained with superforced operation of a tube oscillator with a nominal oscillatory power of 60 kW and a current frequency of 5.28 MHz. The obtained results open up new possibilities for studying the degassing and rheological properties of natural volcanic-rock melts. [ABSTRACT FROM AUTHOR]

The magnetization of most magnetic materials decreases monotonically with increasing temperature. In this work, we found that the temperature coefficient of magnetization of Mn _4- _x Ga _x C alloys can be tuned from negative values to positive values by controlling the composition x . The antiperovskite-type Mn _4- _x Ga _x C (0.05≤ x ≤0.75) alloys were prepared by using induction melting method, which is more efficient in large-scale production and obtaining full-density alloys in comparison with the traditional solid-state-reaction method. The values of the temperature coefficient of magnetization of Mn _4- _x Ga _x C change continuously from negative to positive with decreasing x . The Mn _4- _x Ga _x C alloys with highly thermal-stable magnetization is expected to present in the composition range of 0.15< x

Vacuum induction melting in a refractory crucible is an economical method to produce TiAl-based alloys, aiming to reduce the preparation cost. In this paper, a Sr2CeZrO6 refractory was synthesized by a solid-state reaction method using SrCO3, CeO2 and ZrO2 as raw materials, and its interaction with TiAl alloy melt was investigated. The results showed that a single-phase Sr2CeZrO6 refractory could be fabricated at 1400 °C for 12 h, and its space group was Pnma with a = 5.9742(3) Å, b = 8.3910(5) Å and c = 5.9069(5) Å. An interaction layer with a 40μm thickness and dense structure could be observed in Sr2CeZrO6 crucible after melting TiAl alloy. Additionally, the interaction mechanism showed that the Sr2CeZrO6 refractory dissolved in the alloy melt, resulting in the generation of Sr3Zr2O7, SrAl2O4 and CeO2−x, which attached to the surface of the crucible.

The possibility of the shell-forms' appearance in Cu-Fe alloys at low concentrations of iron (up to 1 wt.%) in samples under conditions of melt rapid cooling (≅ 1⋅103 K/s) and in macrosamples at a low cooling rate (≅ 1⋅101 K/s) is revealed. As found, during the rapid cooling, formations with a copper core and an iron-based shell with sizes up to 50 μm are formed in the samples. As established, in the cast alloy Cu-0.75 wt.% Fe (mass of 0.8 kg) melted under certain conditions in a high-frequency induction furnace with a graphite crucible and cooled in a casting mould at speed of ≅ 10 K/s, there is form-similar formations with a copper core in an iron shell, but with smaller size up to 5 μm as well as larger ones (35 μm) surrounded by a shell of iron with a core consisting of solutions of Cu in Fe and Fe in Cu. As determined, during the process of induction (20 kHz) smelting in a furnace with a silicon carbide crucible of Cu-10.0 wt.% Fe alloy, due to the action of electromagnetic and surface tension forces, successive operations, there is the formation of two separate macrovolumes of phases based on Cu and Fe under certain conditions of their location in the crucible and supply to the crystallizer as well as the appropriate mode of extracting the alloy from it, obtaining continuously cast bimetallic rod (diameter of 7⋅10-3 m, length of 6 m and mass of 1.35 kg) with a copper core in an iron shell. As established, as a result of the used methods of melting and casting, along the length of the rod, two areas with a different shape of the surface iron layer are appeared. Along the first section (length of ≅ 3 m), the shell of a three-layer structure (an outer layer of iron, a middle layer and an inner layer with increasing content of dissolved copper) with a thickness of ≅ 500 μm changes successively to a single-layer iron with a final thickness of 10 μm. The next section is extended to the end of the rod, and the shell has a discontinuous (island) shape with a thickness of ≅ 5 μm at the beginning and ≅ 3 μm at the end. Separate compact formations with a thickness of up to 50 μm are also present. The core layer adjacent to the shell of the first section consists of small (3 μm) copper crystals and copper solution in iron ones and has a thickness of ≅ 65 μm. In the second section, such a layer in the core is absent. The core in both areas consists of dendrites oriented along the rod axis and Cu + Cu2O eutectics. Objects of practical application of the obtained bimetallic rod structures can be cast blanks for the fabrication of contact welding electrodes, cables, wires, catalysts, etc. [ABSTRACT FROM AUTHOR]

The peculiarities of the initial stage of interaction of an iron solid additive (1% by mass) with a copper melt in the process of induction smelting are investigated. Some characteristics influence of the additive relative to liquid copper (structure, temperature dependence of density, specific electrical resistance, magnetic permeability) at the process initial stage of its dissolution in the conditions of melting in an induction furnace with a graphite crucible with laminar movement of the melt and a uniform rise in its temperature from 1.07 to 1.29 of the copper melting temperature. As established, during the first 30 seconds of contact of the additive (armco iron cylinder weighing 8 g with a temperature of 293 K) with liquid (1448 K) copper, liquid phases appeared that did not mix with it and remained in the alloy until the end (30 min) of melting. Dissolution of Fe took place in a mixed mode, with kinetic and diffusive processes proceeding in parallel. Immediately after the contact of Fe with Cu, due to both heat transfer from the melt and the action of a high-frequency (44 kHz) electromagnetic field, a very thin (up to 5-10-5 m) surface layer of iron, which was in a ferromagnetic state, heats up sharply. Overheating the additive above the Curie point reduces the intensity of the field effect on its surface layer, but the concentrated effect of the electromagnetic field is supported by the development of electro-eddy currents directly near the surface of the additive. As found, raising the temperature of the melt to 1643 K intensified the dissolution and spread of both liquid and solid microvolumes in the alloy base and saturation of the melt with oxygen. Taking into account the obtained results, the most favourable melting temperatures are the range of 1523-1623 K when determining the optimal melt mixing intensity level. To create conditions for the formation of microemulsified, suspension or bimetallic structures, they can be implemented in ingots during the development of special technological methods. [ABSTRACT FROM AUTHOR]

Innovative technologies require the use of materials that meet increasingly high requirements; one such requirement is the purity of metals. In the case of copper, this translates into a parameter related to electrical conductivity. Traditional metal refining technologies have some limitations that can be eliminated through the use of modern melting aggregates. Such solutions include vacuum induction furnaces, comprising an induction furnace with a cold crucible. As part of this work, the possibilities of refining copper and lead alloys were investigated. In addition, the research was carried out with the use of two induction vacuum aggregates, allowing us to compare their effectiveness. The tests were carried out in a pressure range of 10–1000 Pa and at temperatures of 1273–1473 K. The results obtained made it possible to determine the mass transport coefficient of lead from an alloy with copper, and to determine the share of resistance in individual stages of the process. For experiments conducted inside an induction crucible furnace, lowering the working pressure inside the furnace chamber from 1000 to 10 Pa while increasing the temperature from 1323 to 1473 K was accompanied by a drop in the lead concentration inside the alloy of 69 to 96%, compared to its initial mass. For experiments conducted inside a cold crucible furnace, approximate values of lead removal appeared for lower temperatures (1273 to 1323 K), confirming that the analyzed process happens faster in this aggregate. [ABSTRACT FROM AUTHOR]

Considering the high melting point and high stability of SrO, it has potential applications in the field of the preparation of titanium alloys. To improve the hydration resistance, SrO samples with different ZrO2 additions were fabricated after firing at 1 750 t for 6 h. The phase, the microstructure, and the hydration resistance of the samples were researched. The results show that the sample with 33 moP/o ZrO2 addition possesses good hydration resistance with the mass gain after hydration for 13 days of less than 0.42 mass°/o. The SrO crucible with 33 moP/o ZrO2 addition does not react with TiNi alloy melt during melting, which provides a support for searching new refractories with good hydration resistance for induction melting titanium alloys. [ABSTRACT FROM AUTHOR]

We report the preparation of bulk ingots of a spin-polarized Ti2MnAl zero-gap semiconductor (Heusler alloy). Ti2MnAl was prepared from elemental titanium, manganese, and aluminum by levitation melting via high-frequency induction heating in an argon atmosphere and by electric-arc skull melting in a helium atmosphere. The melt solidification mechanism and kinetics have been studied in detail. [ABSTRACT FROM AUTHOR]

Vacuum induction melting is a potential process for the preparation of TiAl alloys with good homogeneity and low cost. But the crucial problem is a selection of high stability refractory. In this study, a BaZrO 3 /Y 2 O 3 dual-phase refractory was prepared and its performance for melting TiAl alloys was studied and compared with that of a Y 2 O 3 refractory. The results showed the dual-phase refractory consisted of BaZr 1- x Y x O 3-δ and Y 2 O 3 (ZrO 2), exhibited a thinner interaction layer (30 μm) than the Y 2 O 3 refractory (90 μm) after melting the TiAl alloy. Although the TiAl alloys melted in the dual-phase and Y 2 O 3 refractory exhibited similar oxygen contamination (<0.1 wt%), the alloy melted in the dual-phase refractory had smaller Y 2 O 3 inclusion content and size than that in the Y 2 O 3 refractory, indicating that the dual-phase refractory exhibited a better melting performance than the Y 2 O 3 refractory. This study provides insights into the process of designing highly stable refractory for melting TiAl alloys. [ABSTRACT FROM AUTHOR]

The present study is devoted to the Mn 2.4 Fe 0.8 Al 0.8 and Mn 2 FeAl alloys prepared by induction melting and studied in their original and subsequently annealed states. The annealing was carried out at 773 K/100 h and 1073 K/100 h in the argon atmosphere. The microstructure, phase composition, magnetic properties, and atom arrangement are followed with regard to Mn content and annealing conditions. The scanning electron microscopy completed by the energy dispersive X-ray spectroscopy and neutron activation analysis has detected single-phase alloys with compositions close to the nominal ones. Their structure, analyzed by X-ray diffraction, was found to be primitive cubic β -Mn with the lattice parameters of 0.6359(2) nm for Mn 2.4 Fe 0.8 Al 0.8 and 0.6339(1) nm for Mn 2 FeAl. The coherent potential approximation calculations and positron annihilation spectroscopy have allowed obtaining an overview to the arrangement of Mn, Fe, and Al atoms in the β -Mn structure and formation of the open volume defects. It is shown that Mn atoms occupy predominantly 8c Wyckoff sites and remaining Mn, Fe and Al atoms occupy 12d sites in equal 1/3 proportion. The open volume defects, vacancies and vacancy clusters, occur in both alloys and both annealed states in a very low concentration. From the magnetic viewpoint, both alloys in the as-prepared state and after annealing at 773 K/100 h are paramagnetic at room temperature with transition to antiferromagnetic state at about 30–40 K. The ac susceptibility measurements have indicated spin glass nature of the Mn 2 FeAl alloys. The annealing at a higher temperature, 1073 K/100 h, has affected mainly Mn 2.4 Fe 0.8 Al 0.8 alloy manifesting a weak ferro-/ferrimagnetic contribution at room temperature contributing to a strong magnetic ordering below 42 K. • Mn 2.4 Fe 0.8 Al 0.8 and Mn 2 FeAl alloys produced by induction melting technique. • Prepared ingots annealed for 100 h at 773 K and 1073 K in argon atmosphere. • β-Mn structures with similar lattice constants detected for both types of alloys. • As-Cast and annealed Mn 2·4 Fe 0·8 Al 0.8 and Mn 2 FeAl alloys do not contain any defects. • Mn 2·4 Fe 0·8 Al 0.8 alloy annealed at 1073 K exhibits a ferromagnetic phase below 40 K. [ABSTRACT FROM AUTHOR]

In this study, the copper doping effect on the NiAl structural stability, strength, and electronic structure was investigated. The samples were prepared using induction melting at 2073 K. This material presents good mechanical and physical properties such as heightemperature strength, fatigue or impact, and corrosion resistance which meet technical requirements of many applications. The microstructure of the Cu-doped nickel aluminide was studied using a metallurgical microscope and its lattice parameter was also studied and characterized using an X-ray diffractometer for different concentrations of Cu. The lattice constant of the existing phases was calculated, and it was found that the lattice distortion and gamma prime phase energy have high values allowing the increase of the entropy term of the alloy and subsequently increasing its hardness. From the ab-initio calculation, it was determined that the Cu atoms have the Al sites as a preferred site and prefer to bond with Ni atoms which leads to the improvement of the material hardness. Ab-initio density functional theory was applied to study the formation energy that revealed increasing with Cu amount. [ABSTRACT FROM AUTHOR]

An inductive conduction heating process to heat the extruder in wire additive manufacturing is explored through numerical simulation and an in situ infrared imaging. The 2 D Finite Element Method (FEM) based simulation model provides insights into extruder heating in the inductive conduction heating process. The precise temperature control in the extruder can help achieve the efficient flow of material from extruder. The induction coil design variations to control the extruder temperature are computed numerically to obtain an approximate solution thus offers time and cost-saving. The presented study considers the number of turns of coil, coil radius and coil configurations as the induction coil design parameters whereas coil current, and current frequency are considered to be constant. Based on the results, the design of extruder and geometry of induction coil assembly is proposed to efficiently bring the feed material (Al-5356) to semi-solid state. A thermal imaging method is implemented using an infrared camera to analyse the evolution of thermal fields during extruder heating. Comparison of the extruder tip temperature from simulation and experiments shows an agreeable match with a variation of 8.57%. [ABSTRACT FROM AUTHOR]

A mathematical model is presented for the motion of solid particles in a borosilicate glass melt using cold hearth melting. The spatial distribution and deposition of noble-metal particles in industrial induction conical and flat-bottom furnaces is studied. The advantage of a conical-bottom furnace for retention of dispersed particles in the melt in suspension and their removal with discharged glass is shown. The obtained results are confirmed experimentally. [ABSTRACT FROM AUTHOR]

Al-5Cu belongs to the group of 2xxx series Al-based alloys and has a wide range of uses in the automotive and aerospace industries due to its light weight. The most prominent properties of Al-5Cu alloys are low density, high melting temperature, good thermal conductivity, high strength and toughness. We aimed to improve the mechanical properties of the Al-5Cu alloy. For this reason, the wt. 0.5 and 1.0% ratio Scandium (Sc) doped Al-5Cu alloy was produced by induction melting method. From the X-ray diffraction (XRD) analysis, while Al and Al2Cu phases were observed in Al-5Cu alloy, Cu2Sc phase was determined in addition to these phases in Sc doped alloys. Scanning electron microscopy (SEM) analysis showed that Sc doping greatly thinned the microstructure of ingot alloys, and also semi-stable acicular θ'-Al2Cu phases were found in Sc doped alloys. In addition, the improvement in mechanical properties observed in alloys was explained by the grain size hardening and precipitation hardening mechanisms. From the nanoindentation test results, it was understood that Sc element greatly improved the Al-5Cu alloy in terms of its mechanical properties. [ABSTRACT FROM AUTHOR]

The interdependent movement of a liquid metal and its surface oxide film, found in the state of elastic stress, in the process of induction melting of the metal in a cylindrical crucible was investigated by the method of direct numerical simulation. The structures of the liquid flows in such a metal, determined for different regimes of its induction melting, are presented, and an analysis of the state of the surface of the metal melted in these regimes is given. The equation for the balance of the volume forces in the film covering the whole surface of a molten metal as well as the equations for the displacements and deformations of this film under certain conditions have been derived. The elastic properties of an oxide film on the surface of a liquid metal were estimated on the basis of the experimental data on its induction melting. The interrelation between the liquid flow near the surface of a melt and the volume forces in the film on its surface, the mechanical stress of this film, and its deformations was demonstrated for typical technological regimes of melting of metals. A computational experiment has shown that the model of the stressed state of a film on the surface of a melt, developed, is correct and can be used for the definition of the elastic stresses in such films. The influence of the diffusion parameter of the magnetic field in a melt and its Hartmann number on the elastic deformations of the film on the surface of the melt was determined and the relation between these deformations and the structure of the liquid flow at the surface of the melt was investigated. [ABSTRACT FROM AUTHOR]

In this study, a new Sr-Zr oxide refractory was designed and prepared through a solid-state reaction method according to the mole ratio of n(SrO): n(ZrO 2) = 2:1. The results reveal that the Sr-Zr oxide refractory consisted of three phases, i.e. , Sr 2 ZrO 4 , Sr 3 Zr 2 O 7 and SrO. The thermodynamically stable phase Sr 2 ZrO 4 was hard to form completely due to the limitation of reaction kinetics between SrCO 3 and ZrO 2 , and thus Sr 3 Zr 2 O 7 and SrO coexisted in the Sr-Zr oxide refractory. The composite refractory exhibited a good corrosion resistance during the melting of TiNi alloy melts, and only a slight interaction occurred in the refractory crucible after melting, with the formation of a reaction layer (28 μm in thickness). In addition, the oxygen concentration of the prepared TiNi alloys was determined to be only 0.046 wt.%. These results indicate that the Sr-Zr oxide composites have potential to be used as a refractory candidate for the induction melting of high-activity alloys. [ABSTRACT FROM AUTHOR]

Experiments were performed on processing briquetted and non-briquetted shavings of Kh18N10T stainless steel and 07Kh12NMBF (EP609) and KhN70VMTYuF (EI617) heat-resistant alloys in induction furnaces and electroslag furnaces. It is shown that the most preferable is the technology of simultaneous remelting of a consumable electrode from lump wastes and shavings in an electroslag crucible furnace. In this case, at melting in 120 kg furnace at the amount of shavings fed for melting, equal to 45…55 % of the total melt mass, the specific power consumption is equal to 0.55…0.65 kW/.h/kg, productivity is 130…160 kg/h, and burnout losses are not more than 1…2 %. At electroslag crucible melting it is possible to actively conduct such metallurgical operations as refining, modification, alloying and deoxidation that allows producing high quality metal. [ABSTRACT FROM AUTHOR]

On the example of the alloy Ti15.4Zr30.2Mn44V5.4Сr5, the technological scheme of producing massive ingots by the technique of induction melting in open Al2O3 crucibles, which can be used in industry, is developed. This scheme ensures the absence of significant interaction between the crucible material and the melt, while maintaining the allowable content of aluminium impurities in the alloy, and thus achieving the required structure, phase composition, and hydrogen storage properties. [ABSTRACT FROM AUTHOR]

Innovative technologies require the use of materials that meet increasingly high requirements; one such requirement is the purity of metals. In the case of copper, this translates into a parameter related to electrical conductivity. Traditional metal refining technologies have some limitations that can be eliminated through the use of modern melting aggregates. Such solutions include vacuum induction furnaces, comprising an induction furnace with a cold crucible. As part of this work, the possibilities of refining copper and lead alloys were investigated. In addition, the research was carried out with the use of two induction vacuum aggregates, allowing us to compare their effectiveness. The tests were carried out in a pressure range of 10–1000 Pa and at temperatures of 1273–1473 K. The results obtained made it possible to determine the mass transport coefficient of lead from an alloy with copper, and to determine the share of resistance in individual stages of the process. For experiments conducted inside an induction crucible furnace, lowering the working pressure inside the furnace chamber from 1000 to 10 Pa while increasing the temperature from 1323 to 1473 K was accompanied by a drop in the lead concentration inside the alloy of 69 to 96%, compared to its initial mass. For experiments conducted inside a cold crucible furnace, approximate values of lead removal appeared for lower temperatures (1273 to 1323 K), confirming that the analyzed process happens faster in this aggregate.

Hf-free ZrxTi1−xNiSn0.98Sb0.02 (x = 0.25, 0.5, 0.75) n-type half-Heusler (HH) thermoelectric materials were synthesized by a serial processing method including induction melting (IM), annealing, ball milling, and spark plasma sintering (SPS). For comparison, a Hf-containing half-Heusler Hf0.25Zr0.25Ti0.5NiSn0.98Sb0.02 ingot was also alloyed by arc melting, and the effects of Hf on the thermoelectric properties were estimated. The ZrxTi1−xNiSn0.98Sb0.02 HH materials were nearly pure according to the x-ray diffraction analysis, but microscopic investigation revealed impurity phase inclusions of unalloyed Sn, Zr, and Ti. The power factor (PF) of the Hf-free HH materials reached the maximum value of 4.31 mWm−1 K−2 at 823 K in Zr0.75Ti0.25NiSn0.98Sb0.02, which was higher than Hf0.25Zr0.25Ti0.5NiSn0.98Sb0.02 (4.01 mWm−1 K−2 at 773 K) in this study. However, the thermal conductivity of the Hf-free samples was significantly higher, by which the maximum dimensionless figure of merit was slightly lower (ZTmax = 0.92 in Zr0.75Ti0.25NiSn0.98Sb0.02 at 873 K) than that of Hf0.25Zr0.25Ti0.5NiSn0.98Sb0.02 (ZTmax = 1.03 at 873 K). The thermal conductivity was decomposed into lattice and electronic contributions, and the possible correlation with Ni off-stoichiometry is discussed. [ABSTRACT FROM AUTHOR]

Crystalline phases are promising materials (matrices) for isolating nuclear waste with long-lived radionuclides, actinides first of all. Melting in an induction-heated cold crucible was used to produce a potential matrix with the following nominal composition: 50 wt % TiO2, 10 wt % MnO, 10 wt % CaO, 5 wt % Al2O3, 5 wt % Fe2O3, 10 wt % ZrO2, and 10 wt % CeO2 (actinide simulator). The target murataite phase is the predominant phase in the sample; crichtonite and glass are present as well. The emergence of glass is due to contamination of the melt by the refractory coating of the crucible. As in other samples produced by melting, murataite is represented by zonal crystals, the center of which is enriched in heavy elements (Zr and Ce). Murataite accounts for up to 80% of simulated radioactive waste. Irradiation with a dose of 22 million Gray resulted in partial amorphization of crichtonite. According to the results of a dynamic test (single pass flow test, SPFT), the rate of Ce leaching (powder, water, 70°C) is 10–4–10–5 g/(m2 day). [ABSTRACT FROM AUTHOR]

• Perforated core barrel lower head sample interacted with molten corium was tested. • Thermal shielding sample interacted with molten corium was investigated. • Corium properties for experiments were calculated using ASTEC code. • Solidified corium melt was analysed using scanning electron microscopy. After the Fukushima Daiichi accident, many countries worldwide conducted stress tests for nuclear power plants (NPPs) in operation. These tests initiated back-fitting activities. One of the long-term back-fitting tasks for VVER-1000 reactors involves managing the ex-vessel phase of a hypothetical severe accident (SA). The challenge is to cool down the corium ejected into the reactor cavity after a reactor pressure vessel (RPV) failure by spreading it onto the dedicated area. However, to transport the corium to this area, the thermal shielding must withstand the load of poured corium. The thermal shielding ability must be investigated to maintain this strategy successfully. Moreover, the internal RPV parts may prolong the time of RPV failure and decrease the temperature of the corium ejected from the failed RPV. This phenomenon needs to be verified experimentally. Therefore, the interaction of simulated corium with the internal RPV parts and thermal shielding samples was studied experimentally. These experimental findings may help to understand the corium behavior and its cooling during severe accidents in VVER-1000 reactors. [ABSTRACT FROM AUTHOR]

This paper presents the results of creating and testing a numerical dynamic model of startup heating during induction melting in a cold crucible. The developed model allows one to determine the electric and thermal characteristics of induction furnace in a cold crucible in the dynamic mode, which include distribution of heat sources in the furnace elements, temperature distribution in the melt and the startup material, the distribution and direction of the velocity in the melt, the electrical parameters of the inductor, and the startup heating time and output time to steady state melting. The created model allows one to evaluate the thermal stability of melting without conducting experiments, which is especially important, for instance, in the development of high-level waste vitrification installations. The results of simulation of the startup heating of glass in a cold crucible with an internal diameter of 200 mm at a current frequency of 1.76 MHz are considered. [ABSTRACT FROM AUTHOR]

The effect of Ta and W additions on microstructure and mechanical properties of tilt-cast Ti-45Al-5Nb-2C (at.%) alloy was investigated. Three alloys with nominal composition Ti-45Al-5Nb-2C-2X (in at.%), where X is Ta or W, were prepared by vacuum induction melting in graphite crucibles followed by tilt casting into graphite moulds. The microstructure of the tilt-cast alloys consists of the α2(Ti3Al) + γ(TiAl) lamellar grains, single γ phase, (Ti,Nb,X)2AlC particles with a small amount of (Ti,Nb,X)C, and β/B2 phase identified only in W containing alloy. The EDS analysis shows that Ta segregates into the carbide particles and reduces dissolution of Nb in both (Ti,Nb,Ta)C and (Ti,Nb,Ta)2AlC phases. The alloying with W reduces Nb content in both carbide phases and leads to stabilisation of β/B2 phase in the lamellar α2 + γ regions. The alloying with Ta and W does not affect the volume fraction of the carbide particles but influences their size and morphology. While the alloying with Ta and W has no significant effect on Vickers hardness and the indentation elastic modulus of the studied alloys, the addition of Ta affects the nanohardness and elastic modulus of the (Ti,Nb,Ta)2AlC phase. The addition of W significantly increases the Vickers microhardness of the lamellar α2 + γ regions.

The aim of this work was to obtain dense Cu2S superionic thermoelectric materials, homogeneous in terms of phase and chemical composition, using a very fast and cheap induction-melting technique. The chemical composition was investigated via scanning electron microscopy (SEM) combined with an energy-dispersive spectroscopy (EDS) method, and the phase composition was established by X-ray diffraction (XRD). The thermoelectric figure of merit ZT was determined on the basis of thermoelectric transport properties, i.e., Seebeck coefficient, electrical and thermal conductivity in the temperature range of 300–923 K. The obtained values of the ZT parameter are comparable with those obtained using the induction hot pressing (IHP) technique and about 30–45% higher in the temperature range of 773–923 K in comparison with Cu2S samples densified with the spark plasma sintering (SPS) technique.

The influence of a REM-containing Insteel 7 complex modifier on the structure and the contents of dissolved gases and sulfur in Fe–Al alloys with an increased aluminum content (11–15 wt %) melted in an open induction furnace is studied. [ABSTRACT FROM AUTHOR]

A new generation of Mg-based metallic alloys appears to be particularly promising in the field of biocompatible materials. These alloys have a controlled biodegradability in biological or living fluids. In this paper, nine Mg–Ca–Zn alloys with different chemical compositions were produced and analysed. The production of magnesium alloys by conventional technologies invariably introduces impurities from the refractory lining, which is not permitted in medical systems to be implanted into the human body. During levitation melting, the metal is maintained inside the inductor at a certain distance from the coil, avoiding the contact with any other material, by the action of induction currents. The induction currents cause the mixing of the chemical elements inside the melt, providing the homogeneity of the alloy. The alloys were produced in the levitation induction melting furnace under controlled atmosphere. By combining the effects generated by the magnetic field created in metallic parts, there was possible to hold, heat and melt solid material inside a specifically designed inductor fed by a medium frequency converter. The EDS analysis revealed the chemical compositions, and microhardness tests HV0.1 and microstructural analysis were performed in order to establish the hardening effects and the homogenization degree of the solid solutions. [ABSTRACT FROM AUTHOR]

The movement of a metal melt in an inhomogeneous high-frequency magnetic field is considered. A system of equations with boundary conditions defining the diffusion of the magnetic field and the heat conduction in such a melt in the Boussinesq approximation with account of the Joule heat released in the melt and the volume Lorentz forces acting in it is presented. The correctness of the mathematical model proposed is demonstrated. The amplitude distributions of the magnetic fields of the eddy currents induced in a metal melt, the velocity distributions of the heat flows in it, and the distribution of temperatures in the melt were calculated for the control parameters of its flow determined by the frequency and amplitude of the alternating magnetic field acting on it. The conditions under which the structure of this flow is completely determined by the parameters of the magnetic field and the problem on determination of the heat and mass transfer in the metal melt can be reduced to the calculation of its forced convection in the Lorentz force field and the temperature distribution in the melt at a definite velocity of its flow were determined. [ABSTRACT FROM AUTHOR]

One of the promising technology that guarantee the high-purity of the processed metal is induction skull melting. The quality of the melting process within such a system strongly depends on the cold crucible design. Hence, the experimental investigation of the cold crucible melting was performed. The experimental investigation was performed for various initial mass of the load. The results of that analysis were used for the assessment of the alloy temperature during the process, free surface shape and the area as well as the liquid metal emissivity. The collected results of the thermal analysis showed that the temperature of molten metal increased within the power input increase. Moreover, results of that analysis showed that the characteristic tooth-shaped jags were created mostly at the centre of the cold crucible segments. In addition, experimental results are suitable for the numerical models validation and further investigation of the cold crucible design. [ABSTRACT FROM AUTHOR]

The numerical relation of cast iron chill characteristics (distance of chilled layer H and volume quota of ledeburite in it Ql) with its carbon equivalent СE was investigated. This data helps forecast the evolution of the surface chilled layer forming at the casting production with different thickness from cast iron of various chemical compositions. The study focuses on the unalloyed induction-melted cast iron with eight chemical-composition variants with carbon equivalent from 3.30 up to 5.53%. From these cast irons, step-by-step castings were made with steps sizes of 10 × 60 mm and thickness of 5, 10, 20, and 40 mm. The chilled-layer distance (depth) was measured at the casting fractures and gaged on thickness of full chill zone. Ledeburite volume quota was detected by a metallographic method using the "Nexsys-Image expert pro 3" computer program. According to experimental data, when the casting thickness is 5 and 10 mm, the through (at all thickness) full chill is formed at a carbon equivalent ≤4.08% and ≤3.67%, consequently. At the castings with 20- and 40-mm thickness, the zone of full chill is absent. In this case, the chilled layer depth increases with a decrease of carbon equivalent and decreases with an increase of casting's thickness X. The dependence of H from CE have the exponential character and can be described by the equation H = Aexp(–kCE), where A and k are empirical coefficients. Ledeburite volume quota near the contact casting surface with chiller is near 90%, but it decreases with different intensity depending on changes of carbon equivalent and casting's thickness with an increase in the distance from the surface. By mathematical processing of the experimental data received for the 5-mm distance from the contact surface of the casting with chiller, a numerical relation Ql in casting chilled layer with value of CE can be described by the exponential dependence: Ql = 1000(7/(X + 10))exp(–CE). [ABSTRACT FROM AUTHOR]

Demand of special combination of different properties of the materials instigated the development of metal matrix composite. The carbon nanotubes being renowned for their excellent physical and mechanical properties are one of the major choices as strengthen material for metal matrix composites. To benefit their properties, the carbon nanotubes should be thoroughly dispersed and have wetting with the matrix. In the present study, a precursor of aluminum-carbon nanotubes was prepared by coating the nanotubes with titanium and used to fabricate the composite by induction melting. The precursor provided easy wetting, while induction melting facilitated dispersion of the nanotubes readily. Consequently, the composite exhibited noticeable augmentations in yield and tensile strength from 64 to 193 MPa and 81 to 227 MPa, respectively. [ABSTRACT FROM AUTHOR]