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Metals
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Solidification Process of Alloys under Magnetic Field
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Solidification Process of Alloys under Magnetic Field

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 7734

Special Issue Editor

Prof. Dr. Yves R. Fautrelle

E-Mail Website
Guest Editor
SIMaP Laboratory, Grenoble-Alpes University, BP 75, 38402 Saint Martin d’Hères CEDEX, France
Interests: electromagnetic/magnetic processing of materials; solidification under magnetic fields

Special Issue Information

Dear Colleagues,

In metallurgy, current trends are oriented toward productivity gains, controlling the quality of solidified material, and development of environmentally friendly processes. This has two aspects. We seek to minimize internal defects such as segregations, inclusions, and porosities, responsible for the degradation of the properties of the material. Then, the possibility of controlling with precision its internal structure constitutes an important advantage. Finally, the control and automation of processes are crucial issues. Use of alternating or direct magnetic fields offers many possibilities to achieve the above objectives. Such contactless technologies provide an additional guarantee of material quality, cleanliness, and automation.

Magnetic-assisted solidification is crucial for modern techniques such as materials refining, casting of alloys, and semiconductor elaboration, as well as additive manufacturing. Often, the macro-microstructural modulation induced by the magnetic field can lead to drastic improvements in properties. For example, the imposition of a static magnetic field can dampen out flow and reduce turbulence in melts, but also modify flow patterns due to anisotropy effects. Nevertheless, static magnetic fields have also recently been seen to increase convection in the liquid parts of the solidifying material and to exert strong action on the solid, a phenomenon known as thermo-electric magneto-hydrodynamics (TEMHD). Moreover, thanks to the development of technologies for the production of intense magnetic fields, it becomes possible to use them for the production of “soft-magnetic” metallic alloys. Indeed, high magnetic fields lead to a wide variety of effects on the material, such as the structuring/texturing/control of its crystalline orientation.

Alternating magnetic fields are also widely used in the processing of conducting materials. The most widespread application is induction heating of conducting or low-conducting materials such as liquid metals, plasmas, and ionic liquids such as molten glasses or oxides. The most important advantages of induction are cleanliness, heating speed, controllability, and electrical efficiency of the process. Furthermore, the resulting electromagnetic forces can be used to act directly on the material being solidified for liquid stirring, dendrite fragmentation, columnar-to-equiaxed transition, levitation, etc. A large “zoology” of magnetic fields is being developed so as to exert “tailored” actions linked to the process and the material. These are, for example, pulsating, single/polyphase, and modulated magnetic fields.

This Special Issue aims to focus on those traditional or innovative electromagnetic devices capable of improving quality, productivity, cleanliness, energy consumption of existing metallurgical processes, but also capable of developing new environmentally friendly processes for new materials. For this Special Issue, we welcome contributions from both academia and industry.

Prof. Dr. Yves R. Fautrelle
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Magnetic fields
  • Liquid metals
  • Solidification under magnetic fields
  • Electrically conducting materials
  • Electromagnetic processing
  • Soft-magnetic materials
  • Crystal growth

Published Papers (4 papers)

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Research

17 pages, 9889 KiB  
Article
Macrosegregation Evolution in Eutectic Al-Si Alloy under the Influence of a Rotational Magnetic Field
by Kassab Al-Omari, András Roósz, Arnold Rónaföldi, Mária Svéda and Zsolt Veres
Metals 2022, 12(11), 1990; https://doi.org/10.3390/met12111990 - 21 Nov 2022
Cited by 1 | Viewed by 1481
Abstract
Using magnetic stirring during solidification provides a good opportunity to control the microstructure of alloys, thus controlling their physical properties. However, magnetic stirring is often accompanied by a change in local concentrations, and new structures form which could harm the physical properties. This [...] Read more.
Using magnetic stirring during solidification provides a good opportunity to control the microstructure of alloys, thus controlling their physical properties. However, magnetic stirring is often accompanied by a change in local concentrations, and new structures form which could harm the physical properties. This research paper investigated the effect of forced melt flow by a rotating magnetic field (RMF) on the macrostructure of an Al-Si eutectic alloy. To serve this purpose, Al-12.6 wt% Si alloy samples were solidified in a vertical Bridgman-type furnace equipped with a rotating magnetic inductor to induce the flow in the melt. The diameter and length of the sample are 8 mm and 120 mm, respectively. The solidification parameters are a temperature gradient (G) of 6 K/m, and the solid/liquid front velocity (v) of 0.1 mm/s. These samples were divided into parts during the solidification process, where some of these parts are solidified under the effect of RMF stirring while others are solidified without stirring. The structure obtained after solidification showed a distinct impact of stirring by RMF; new phases have been solidified which were not originally present in the structure before stirring. Besides the eutectic structure, the new phases are the primary aluminum and the primary silicon. The Si concentration and the volume fraction of each phase were measured using Energy-Dispersive Spectroscope (EDS)and new image processing techniques. The experimental results reveal that applying the RMF during the solidification has a distinct effect on the macrostructure of Al-Si eutectic alloys. Indeed, the RMF provokes macro-segregation, reduces the amount of eutectic structure, and changes the sample’s Si concentration distribution. Full article
(This article belongs to the Special Issue Solidification Process of Alloys under Magnetic Field)
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18 pages, 4008 KiB  
Article
New Equipment and Method for Refining the Solidified Grain Structure
by Arnold Rónaföldi, Zsolt Veres, Mária Svéda and András Roósz
Metals 2022, 12(4), 658; https://doi.org/10.3390/met12040658 - 12 Apr 2022
Viewed by 1384
Abstract
The mechanical properties of solidified alloys strongly depend on the grain size. In many practical cases at the given solidification parameters (temperature gradient and solid/liquid interface velocity), the solidified microstructure is columnar, meaning that the mechanical properties differ depending on the direction, which [...] Read more.
The mechanical properties of solidified alloys strongly depend on the grain size. In many practical cases at the given solidification parameters (temperature gradient and solid/liquid interface velocity), the solidified microstructure is columnar, meaning that the mechanical properties differ depending on the direction, which results in the material being unsuitable for application. The microstructure can be changed from columnar to equiaxed through the inclusion of grain refinement material. This strategy is well known in the literature as the columnar/equiaxed transition (CET). In some cases, it is beneficial if the CET can be produced without using grain refinement material; for example, it may detrimentally affect the mechanical properties (such as when the Al alloy ingot is used in pressing). The stirring of the melt as an alternative for the use of grain refinement material could solve this problem as intensive melt flow can break some particles from growing dendrites. This paper demonstrates a new type of traveling magnetic field inductor that is used to produce strong shearing stress in the flow perpendicular to the solidification front by causing part of the metallic melt layers touching each other to flow in an opposite direction. Through some examples, we demonstrate the effect of stirring by the new inductor on the solidified grain structure. Full article
(This article belongs to the Special Issue Solidification Process of Alloys under Magnetic Field)
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13 pages, 4291 KiB  
Article
Impact of a Transient and Asymmetrical Distribution of the Electric Arc on the Solidification Conditions of the Ingot in the VAR Process
by Pierre-Olivier Delzant, Pierre Chapelle, Alain Jardy, Alexey Matveichev and Yvon Millet
Metals 2022, 12(3), 500; https://doi.org/10.3390/met12030500 - 16 Mar 2022
Cited by 4 | Viewed by 1794
Abstract
Vacuum Arc Remelting is an important method of processing reactive and refractory liquid metal alloys, including titanium and zirconium alloys. Recent measurements of the electric arc dynamics under the presence of a time-varying magnetic field during an industrial melt of a Ti64 alloy [...] Read more.
Vacuum Arc Remelting is an important method of processing reactive and refractory liquid metal alloys, including titanium and zirconium alloys. Recent measurements of the electric arc dynamics under the presence of a time-varying magnetic field during an industrial melt of a Ti64 alloy provided evidence of the existence of an ensemble arc motion. Such motion is responsible for transient and non-axisymmetric inputs of electric current and energy at the top surface of the remelted ingot. The present work is an attempt to evaluate, using a simplified numerical simulation approach, to what extent the solidification conditions of the VAR ingot and, consequently, the quality of the final product, may be affected by this phenomenon. The reported results indicate that, under the worst case conditions, the relative vanadium segregation in the solidified ingot can reach values as high as 12.5%. Full article
(This article belongs to the Special Issue Solidification Process of Alloys under Magnetic Field)
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17 pages, 7529 KiB  
Article
Effects of Static Magnetic Field on the Microstructure of Selective Laser Melted Inconel 625 Superalloy: Numerical and Experiment Investigations
by Wanli Zhu, Sheng Yu, Chaoyue Chen, Ling Shi, Songzhe Xu, Sansan Shuai, Tao Hu, Hanlin Liao, Jiang Wang and Zhongming Ren
Metals 2021, 11(11), 1846; https://doi.org/10.3390/met11111846 - 17 Nov 2021
Cited by 9 | Viewed by 2137
Abstract
A number of researchers have reported that a static magnetic field (SMF) will affect the process of selective laser melting (SLM), which is achieved mainly through affecting molten pool evolution and microstructure growth. However, its underlying mechanism has not been fully understood. In [...] Read more.
A number of researchers have reported that a static magnetic field (SMF) will affect the process of selective laser melting (SLM), which is achieved mainly through affecting molten pool evolution and microstructure growth. However, its underlying mechanism has not been fully understood. In this work, we conducted a comprehensive investigation of the influence of SMF on the SLM Inconel 625 superalloy through experiments and multi-scale numerical simulation. The multi-scale numerical models of the SLM process include the molten pool and the dendrite in the mushy zone. For the molten pool simulation, the simulation results are in good agreement with the experimental results regarding the pool size. Under the influence of the Lorentz force, the dimension of the molten pool, the flow field, and the temperature field do not have an obvious change. For the dendrite simulation, the dendrite size obtained in the experiment is employed for setting up the dendrite geometry in the dendrite numerical simulation, and our findings show that the applied magnetic field mainly influences the dendrite growth owing to thermoelectric magnetic force (TEMF) on the solid–liquid interface rather than the Lorentz force inside the molten pool. Since the TEMF on the solid–liquid interface is affected by the interaction between the SMF and thermal gradient at different locations, we changed the SLM parameters and SMF to investigate the effect on the TEMF. The simulation shows that the thermoelectric current is highest at the solid–liquid interface, resulting in a maximum TEMF at the solid–liquid interface and, as a result, affecting the dendrite morphology and promoting the columnar to equiaxed transition (CET), which is also shown in the experiment results under 0.1 T. Furthermore, it is known that the thermoelectric magnetic convection (TEMC) around the dendrite can homogenize the laves phase distribution. This agrees well with the experimental results, which show reduced Nb precipitation from 8.65% to 4.34% under the SMF of 0.1 T. The present work can provide potential guidance for microstructure control in the SLM process using an external SMF. Full article
(This article belongs to the Special Issue Solidification Process of Alloys under Magnetic Field)
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