Search

The effect of the direct current (DC) on the solidification structure in the directional solidification of Al–15Sn–1Cu alloy under 10 T magnetic field was investigated experimentally and numerically. The experimental results show that coarse columnar grains are observed when no DC is applied. However, the microstructure transforms from columnar dendrites to irregular dendrites, and the columnar-to-equiaxed transition (CET) occurs with the application of DC. The numerical results show that the Lorentz force acting on the dendrites can be increased by the application of DC. Additionally, the torque created by the Lorentz force results in the stress concentration at the roots of dendrites arms. The stress increases with the DC when it is larger than the thermoelectric current. Consequently, the dendrites break into fragments when the stress exceeds a certain value and CET occurs. The results indicate that the application of DC facilitates CET at higher withdrawal speeds. Furthermore, this work may initiate a novel method for CET via applying the DC in directional solidification under 10 T magnetic field. [ABSTRACT FROM AUTHOR]

Atomic diffusion is a natural phenomenon in liquid melt. Avoiding the melt convection is the most challenging when accuracy in measuring the diffusion coefficient of atoms is desired. The diffusion in liquid Al–Cu melts is studied under various static magnetic fields (SMFs). Thermoelectric magnetic convection is induced during the diffusion in the conductive crucible. It is suppressed by increasing the magnetic flux density or eliminated by using an insulated crucible. The interdiffusion coefficient can be accurately measured in the SMF greater than 3 T. The present work provides a new view to study the solidification of alloys under the SMF. [ABSTRACT FROM AUTHOR]

A transverse static magnetic field (TSMF) is implemented in a laboratory electroslag remelting (ESR) experiment to control eutectic carbides morphology of Cr8 die steel herein. Under action of a TSMF, the temperature distribution of the molten pool becomes homogeneous, the local solidification time is shortened, and the interdendritic region space shrinks, which result in an evenly spaced distribution of solute atoms and a reduction in interdendritic segregation. Therefore, the formation and subsequent growth of eutectic carbides are further inhibited, thereby causing the generation of smaller and more uniform distributed eutectic carbides due to the application of the TSMF. Moreover, the increase of the number of Al2O3–(Ti,V)N inclusions serves to be the heterogeneous nucleus of carbides (inclusions also become finer) caused by TSMF, which also contributes to the refinements of eutectic carbides in Cr8 ingots. [ABSTRACT FROM AUTHOR]

A transient two-dimensional (2D) coupled mathematical model was developed to study the effect of external axial static magnetic field (ASMF) on the evolution of metal pool profiles. Electromagnetic flow, heat transfer, and solidification were explored simultaneously in this model. The growth of the ingot was predicted with the dynamic mesh technique. The calculated results indicated that the temperature distribution became more uniform both in slag and metal pool with 0.05-T ASMF. To characterize the metal pool profile more reasonable, the actual depth (H a = H m - H c) is defined to represent the depth of the metal pool. Compared with the case without applying ASMF, the calculated actual metal pool profile was flattened remarkably from 23 to 17.5 mm. Meanwhile, the calculated actual metal pool depth was compared with the measurement, which was from 25.5 to 16 mm, in experiments on a laboratory scale to validate the model. In addition, the mechanisms how ASMF improved the metal pool profile were elaborated thoroughly. Under the interaction of ASMF and the direct current component (DCC), the induced rotating Lorentz force makes the temperature field of slag pool more uniform. As a result, the heat transfer from slag to metal pool becomes more well distributed. On the other hand, the forced flow of metal pool by the drag of slag pool can enhance the effective thermal conductivity of metal pool and then reduce the temperature gradient in radial direction. All of above ultimately lead to a shallower metal pool. [ABSTRACT FROM AUTHOR]

This study investigates the influence of a superimposed axial static magnetic field (ASMF) on the morphology of metal pool and eutectic carbides (ECs) in electroslag remelted M2 high-speed steel (HSS). The application of ASMF caused the metal pool to become shallower, and the solidified structure to expand axially, along with finer (i.e., more uniformly distributed and crystallographically oriented) ECs. Lorentz force-driven unidirectional circulation in slag pool was the primary cause of the metal pool's morphological adjustment; this resulted in a more homogenous temperature distribution in slag pool. Thus, the heat transfer from the slag pool to the metal pool became more uniform, creating a metal pool that is shallower. Additionally, local solidification time (LST) became shorter, while the number of (Ti, V)N-Al2O3 inclusions serving as heterogeneous nuclei for EC formation increased due to ASMF, enabling finer EC with more crystallographic orientations in ESR ingots. [ABSTRACT FROM AUTHOR]

An axial static magnetic field (ASMF) is superimposed during the electroslag remelting (ESR) process to regulate the inclusion removal (GCr15 bearing steel) in the current study. After applying a 50 mT ASMF, the metal pool of the ESR ingot becomes shallower and the solidified dendritic structure tends to grow axially, together with a higher inclusion removal efficiency. The number of inclusions in ESR ingot decreases, and the inclusion with larger size (>10 μm) is almost eliminated. By tailoring the morphology of the liquid melt film (LMF), droplet, and metal pool, the ASMF applied in this study strengthens the kinetic conditions (inclusion migrated to slag/metal interface) for the inclusion removal, thus realizing the multi‐stage enhanced removal of inclusion during ESR process. [ABSTRACT FROM AUTHOR]

• Strong Goss texture was obtained at 6 T without complicated rolling and annealing. • There is a misorientation angle slope in the interior of grain. • Magnetic properties are greatly improved by using high static magnetic field. Fe-4.5 wt% Si alloy was solidified in the presence of an axial high static magnetic field (HSMF) to investigate the influence of magnetic field on the crystal orientation and magnetic property. With the increase of magnetic field intensity (MFI), the crystal orientation of the Fe-4.5 wt% Si alloy turns to 〈1 0 0〉 which is the easy magnetization axis. The specimen with strong Goss texture was obtained under a 6 T HSMF. Moreover, the saturation magnetic induction also increases with the increase of the MFI. The above results are attributed to the effect of the HSMF on the magnetocrystalline anisotropy during bulk solidification. [ABSTRACT FROM AUTHOR]

• The leaching efficiency of Ga and Ge increases continuously with temperature. • Si(OH) 4 is easy to selectively adsorb Ge, which reduces the leaching rate. • The strong magnetic field can change the reaction mechanism of Si(OH) 4. • The strong magnetic field can reduce the insoluble GeO 2 content. • There is an intrinsic correlation in temperature, magnetic field, and ultrasound. Gallium (Ga) and Germanium (Ge) are crucial strategic resources with extensive applications in high-tech industries. However, Ga and Ge primarily occur as associated minerals. The process involves the leaching of lead–zinc ores and subsequent leaching to recover the valuable elements. The conventional acid leaching procedure exhibits low leaching effectiveness for Ga and Ge, making their recovery challenging. This study initially investigated the occurrence states of Ga and Ge. The thermodynamic simulations were used to investigate the feasibility of Zinc powder replacement residue (ZPRR) in a two-stage acid leaching process. The leaching mechanism in the strong magnetic field and ultrasonic field was studied using several characterizations such as XRD, SEM, XPS, FT-IR, etc. The investigation revealed that raising the temperature in the acidic solution led to an enhanced leaching efficiency of Ga and Ge. However, at 120 °C, the leaching efficiency of Ge decreased due to the hydrolytic precipitation occurring between Ge and SiO 2. Nevertheless, the utilisation of a strong magnetic field proved advantageous in impeding this process. Furthermore, the application of the combined ultrasonic field contributed to enhancing the level of residue refining, hence promoting the effectiveness and degree of the reaction. Thus, the leaching efficiency of Ga and Ge was influenced by temperature, strong magnetic field, and ultrasonic field in combination. The high leaching efficiency of 95.53 % and 97.11 % for Ga and Ge, respectively, could be attained in the optimal experimental parameters. This study offers theoretical guidance for the effective and environmentally friendly leaching of Ga and Ge. Furthermore, it has been observed that this method is also promising for leaching the other valuable metals. [ABSTRACT FROM AUTHOR]

• The easy axis of Fe/silicene changes with changing the thickness of Fe. • All the magnetic moments are insensitive to the electric field. • The perpendicular magnetic anisotropy can be enhanced under the electric field. In view of the importance of inducing magnetism and large perpendicular magnetic anisotropy in silicene, the influence of an external electric field on the magnetism and the magnetic anisotropy of the Fe(15, 18, 21 monolayers)/silicene heterostructures are investigated by using first-principles calculations. The results show that the magnetic moments and the magnetic anisotropy of the Fe/silicene heterostructures are mainly from Fe films. With increasing the thickness of Fe film, the easy magnetization axis of the Fe/silicene heterostructure changes from out-of-plane to in-plane direction. In addition, the magnetic moments in all the Fe/silicene heterostructures are insensitive to the electric field. Particularly, under the positive electric field, the perpendicular magnetic anisotropy of the Fe(15 monolayers)/silicene can be enhanced, the magnetic anisotropy of the Fe(18 monolayers)/silicene increases from in-plane magnetic anisotropy to perpendicular magnetic anisotropy, and the magnetic anisotropy of the Fe(21 monolayers)/silicene also increases although its easy magnetization axis is still along in-plane direction. The mechanism of the electric-field-driven modulation of magnetic anisotropy is mainly from the increase of the positive contribution from spin-orbit coupling interaction between opposite spin d z 2 and d yz orbitals of the second Fe layer from the Fe/silicene interface. Our study reveals that the perpendicular magnetic anisotropy can be achieved or enhanced by applying positive electric field if the thickness of Fe film in Fe/silicene heterostructure is suitable. [ABSTRACT FROM AUTHOR]

Static magnetic field is useful in processing materials with various microstructures. A self-designed gravity-assisted automatic docking device was used to study diffusion in liquid Al-Cu melts under various SMFs up to 22 T. SMF reduces the coefficient of interdiffusion (D AlCu) by damping the melt convection, which is more efficient with a horizontal SMF than a vertical SMF. A simulated microgravity is achieved when the SMF is greater than the critical 3 T. The simulated microgravity is in favor of growing a single α-Al dendrite in Al-Cu melt. The physical mechanism, which is called the diffusion-limited favored single crystal growth, is established. The present work provides a potential method in processing the single metallic crystal rapidly in the future. [Display omitted] [ABSTRACT FROM AUTHOR]