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Open AccessEditorial

Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals

by Mohsen Asle Zaeem

Metals 2018, 8(2), 120; https://doi.org/10.3390/met8020120 - 9 Feb 2018

Cited by 1 | Viewed by 3273

Abstract

Solidification occurs in several material processing methods, such as in casting, welding, and laser additive manufacturing of metals, and it controls the nano- and microstructures, as well as the overall properties of the products[...] Full article

(This article belongs to the Special Issue Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals)

Research

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1725 KiB

Open AccessFeature PaperArticle

Detection of Capillary-Mediated Energy Fields on a Grain Boundary Groove: Solid–Liquid Interface Perturbations

by Martin Glicksman and Kumar Ankit

Metals 2017, 7(12), 547; https://doi.org/10.3390/met7120547 - 6 Dec 2017

Cited by 9 | Viewed by 5536

Abstract

Grain boundary grooves are common features on polycrystalline solid–liquid interfaces. Their local microstructure can be closely approximated as a “variational” groove, the theoretical profile for which is analyzed here for its Gibbs–Thomson thermo-potential distribution. The distribution of thermo-potentials for a variational groove exhibits [...] Read more.

Grain boundary grooves are common features on polycrystalline solid–liquid interfaces. Their local microstructure can be closely approximated as a “variational” groove, the theoretical profile for which is analyzed here for its Gibbs–Thomson thermo-potential distribution. The distribution of thermo-potentials for a variational groove exhibits gradients tangential to the solid–liquid interface. Energy fluxes stimulated by capillary-mediated tangential gradients are divergent and thus capable of redistributing energy on real or simulated grain boundary grooves. Moreover, the importance of such capillary-mediated energy fields on interfaces is their influence on stability and pattern formation dynamics. The capillary-mediated field expected to be present on a stationary grain boundary groove is verified quantitatively using the multiphase-field approach. Simulation and post-processing measurements fully corroborate the presence and intensity distribution of interfacial cooling, proving that thermodynamically-consistent numerical models already support, without any modification, capillary perturbation fields, the existence of which is currently overlooked in formulations of sharp interface dynamic models. Full article

(This article belongs to the Special Issue Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals)

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5486 KiB

Open AccessArticle

Experimental and Numerical Investigation of an Overheated Aluminum Droplet Wetting a Zinc-Coated Steel Surface

by Marius Gatzen, Peer Woizeschke, Tim Radel, Claus Thomy and Frank Vollertsen

Metals 2017, 7(12), 535; https://doi.org/10.3390/met7120535 - 1 Dec 2017

Cited by 3 | Viewed by 4378

Abstract

Wetting steel surfaces with liquid aluminum without the use of flux can be enabled by the presence of a zinc-coating. The mechanisms behind this effect are not yet fully understood. Research results on single aluminum droplets falling on commercial galvanized steel substrates revealed [...] Read more.

Wetting steel surfaces with liquid aluminum without the use of flux can be enabled by the presence of a zinc-coating. The mechanisms behind this effect are not yet fully understood. Research results on single aluminum droplets falling on commercial galvanized steel substrates revealed the good wetting capability of zinc coatings independently from the coating type. The final wetting angle and length are apparently linked to the time where zinc is liquefied during its contact with the overheated aluminum melt. This led to the assumption that the interaction is basically a fluid dynamic effect of liquid aluminum getting locally alloyed by zinc. A numerical model was developed to describe the transient behavior of droplet movement and mixing with the liquefied zinc layer to understand the spreading dynamics. The simulations reveal a displacement of the molten zinc after the impact of the droplet, which ultimately leads to an accumulation of zinc in the outer weld toe after solidification. The simulation approach neglects the effect of evaporating zinc, resulting in a slight overestimation of the final droplet width. However, in terms of spreading initiation during the first milliseconds, the simulation is in good correlation with experimental observations and demonstrates the reason for the good wetting in the presence of zinc coatings. Full article

(This article belongs to the Special Issue Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals)

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8112 KiB

Open AccessFeature PaperArticle

Three-Dimensional Lattice Boltzmann Modeling of Dendritic Solidification under Forced and Natural Convection

by Mohsen Eshraghi, Mohammad Hashemi, Bohumir Jelinek and Sergio D. Felicelli

Metals 2017, 7(11), 474; https://doi.org/10.3390/met7110474 - 3 Nov 2017

Cited by 22 | Viewed by 5870

Abstract

A three-dimensional (3D) lattice Boltzmann (LB) model is developed to simulate the dendritic growth during solidification of Al-Cu alloys under forced and natural convection. The LB method is used to solve for solute diffusion and fluid flow. It is assumed that the dendritic [...] Read more.

A three-dimensional (3D) lattice Boltzmann (LB) model is developed to simulate the dendritic growth during solidification of Al-Cu alloys under forced and natural convection. The LB method is used to solve for solute diffusion and fluid flow. It is assumed that the dendritic growth is driven by the difference between the local actual and local equilibrium composition of the liquid in the interface. A cellular automaton (CA) scheme is adopted to capture new interface cells. The LB models for solute transport and fluid flow are first validated against two benchmark problems. The dendrite growth model is also validated with available analytical solutions. The evolution of a 3D dendrite affected by melt convection is investigated. Also, density inversion caused by solute concentration gradient is studied. It is shown that convection can change the kinetics of growth by affecting the solute distribution around the dendrite. In addition, the growth features of two-dimensional (2D) and 3D dendrites are briefly compared. The results show that decreasing undercooling and increasing solute concentration decelerates the growth in all branches of the dendrite. While increasing fluid velocity does not significantly influence upstream and transverse arms, it decreases the growth rate in the downstream direction considerably. The size ratio of the upstream arm to the downstream arm rises by increasing inlet velocity and solute content, and decreasing undercooling. Similarly, in the case of natural convection, redistribution of solute due to buoyancy-induced flow suppresses the growth of the upward arm and accelerates the growth of the downward arm. Considering the advantages offered by the LB method, the present model can be used as a new tool for simulating 3D dendritic solidification under convection. Full article

(This article belongs to the Special Issue Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals)

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8906 KiB

Open AccessArticle

Three-Dimensional Numerical Modeling of Macrosegregation in Continuously Cast Billets

by Qipeng Dong, Jiongming Zhang, Yanbin Yin and Bo Wang

Metals 2017, 7(6), 209; https://doi.org/10.3390/met7060209 - 6 Jun 2017

Cited by 33 | Viewed by 5888

Abstract

Macrosegregation, serving as a major defect in billets, can severely degrade material homogeneity. Better understanding of the physical characteristics of macrosegregation through numerical simulation could significantly contribute to the segregation control. The main purpose of this study was to predict macrosegregation in continuously [...] Read more.

Macrosegregation, serving as a major defect in billets, can severely degrade material homogeneity. Better understanding of the physical characteristics of macrosegregation through numerical simulation could significantly contribute to the segregation control. The main purpose of this study was to predict macrosegregation in continuously cast billets with a newly developed three-dimensional macrosegregation model. The fluid flow, solidification, and solute transport in the entire billet region were solved and analyzed. Flow patterns, revealing a typical melt recirculation at the upper region of mold and thermosolutal convection at the secondary cooling zone, significantly affect the solidification and solute distribution. The solute redistribution occurring with thermosolutal convection at the solidification front contributes significantly to continued macrosegregation as solidification proceeds. The results of this study show that the equilibrium partition coefficient is mostly responsible for the magnitude of macrosegregation, while comparison between solute P and S indicated that diffusion coefficients also have some amount of influence. Typical macrosegregation patterns containing a positively segregated peak at the centerline and negatively segregated minima at either side were obtained via the proposed three-dimensional macrosegregation model, which validated by the measured surface temperatures and segregation degree. Full article

(This article belongs to the Special Issue Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals)

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3256 KiB

Open AccessArticle

Influence of Growth Velocity on the Separation of Primary Silicon in Solidified Al-Si Hypereutectic Alloy Driven by a Pulsed Electric Current

by Yunhu Zhang, Chunyang Ye, Yanyi Xu, Honggang Zhong, Xiangru Chen, Xincheng Miao, Changjiang Song and Qijie Zhai

Metals 2017, 7(6), 184; https://doi.org/10.3390/met7060184 - 23 May 2017

Cited by 16 | Viewed by 3981

Abstract

Investigating the separation of the primary silicon phase in Al-Si hypereutectic alloys is of high importance for the production of solar grade silicon. The present paper focuses on the effect of growth velocity on the electric current pulse (ECP)-induced separation of primary silicon [...] Read more.

Investigating the separation of the primary silicon phase in Al-Si hypereutectic alloys is of high importance for the production of solar grade silicon. The present paper focuses on the effect of growth velocity on the electric current pulse (ECP)-induced separation of primary silicon in a directionally solidified Al-20.5 wt % Si hypereutectic alloy. Experimental results show that lower growth velocity promotes the enrichment tendency of primary silicon at the bottom region of the sample. The maximum measured area percentage of segregated primary silicon in the sample solidified at the growth velocity of 4 μm/s is as high as 82.6%, whereas the corresponding value is only 59% in the sample solidified at the growth velocity of 24 μm/s. This is attributed to the fact that the stronger forced flow is generated to promote the precipitation of primary silicon accompanied by a higher concentration of electric current in the mushy zone under the application of a slower growth velocity. Full article

(This article belongs to the Special Issue Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals)

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6608 KiB

Open AccessArticle

Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic Stirring

by Piotr Mikolajczak

Metals 2017, 7(3), 89; https://doi.org/10.3390/met7030089 - 10 Mar 2017

Cited by 21 | Viewed by 6566

Abstract

Equiaxed solidification of AlMgSi alloys with Fe and Mn was studied by electromagnetic stirring to understand the effect of forced flow. The specimens solidified with a low cooling rate, low temperature gradient, and forced convection. Stirring induced by a coil system around the [...] Read more.

Equiaxed solidification of AlMgSi alloys with Fe and Mn was studied by electromagnetic stirring to understand the effect of forced flow. The specimens solidified with a low cooling rate, low temperature gradient, and forced convection. Stirring induced by a coil system around the specimens caused a transformation from equiaxed dendritic to rosette morphology with minor dendrites and, occasionally, spheroids. This evolution was quantitatively observed with specific surface S_v. The precipitation sequence of the phases was calculated using the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) technique. Melt flow decreased secondary dendrite arm spacing λ₂ in the AlSi5Fe1.0 alloy, while λ₂ increased slightly in Mg-containing alloys. The length of detrimental β-Al₅FeSi phases decreased only in AlSi5Fe1.0 alloy under stirring, whereas in Mg-containing alloys, changes to the β-Al₅FeSi phase were negligible; however, in all specimens, the number density increased. The modification of Mn-rich phases, spacing of eutectics, and Mg₂Si phases was analyzed. It was found that the occurrence of Mg₂Si phase regions reduced fluid flow in the late stages of solidification and, consequentially, reduced shortening of β-Al₅FeSi, diminished secondary arm-ripening caused by forced convection, and supported diffusive ripening. However, the Mg₂Si phase was found to have not disturbed stirring in the early stage of solidification, and transformation from dendrites to rosettes was unaffected. Full article

(This article belongs to the Special Issue Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals)

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7371 KiB

Open AccessArticle

Effects of EMS Induced Flow on Solidification and Solute Transport in Bloom Mold

by Qing Fang, Hongwei Ni, Bao Wang, Hua Zhang and Fei Ye

Metals 2017, 7(3), 72; https://doi.org/10.3390/met7030072 - 24 Feb 2017

Cited by 42 | Viewed by 7066

Abstract

The flow, temperature, solidification, and solute concentration field in a continuous casting bloom mold were solved simultaneously by a multiphysics numerical model by considering the effect of in-mold electromagnetic stirring (M-EMS). The mold metallurgical differences between cases with and without EMS are discussed [...] Read more.

The flow, temperature, solidification, and solute concentration field in a continuous casting bloom mold were solved simultaneously by a multiphysics numerical model by considering the effect of in-mold electromagnetic stirring (M-EMS). The mold metallurgical differences between cases with and without EMS are discussed first, and then the solute transport model verified. Moreover, the effects of EMS current intensity on the metallurgical behavior in the bloom mold were also investigated. The simulated solute distributions were basically consistent with the test results. The simulations showed that M-EMS can apparently homogenize the initial solidified shell, liquid steel temperature, and solute element in the EMS effective zone. Meanwhile, the impingement effect of jet flow and molten steel superheat can be reduced, and the degree of negative segregation in the solidified shell at the mold corner alleviated from 0.74 to 0.78. However, the level fluctuation and segregation degree in the shell around the center of the wide and narrow sides were aggravated from 4.5 mm to 6.2 mm and from 0.84 to 0.738, respectively. With the rise of current intensity the bloom surface temperature, level fluctuation, stirring intensity, uniformity of molten steel temperature, and solute distribution also increased, while the growth velocity of the solidifying shell in the EMS effective zone declined and the solute mass fraction at the center of the computational outlet (z = 1.5 m) decreased. M-EMS with a current intensity of 600 A is more suitable for big bloom castings. Full article

(This article belongs to the Special Issue Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals)

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Review

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3847 KiB

Open AccessReview

Modeling Inclusion Formation during Solidification of Steel: A Review

by Dali You, Susanne K. Michelic, Peter Presoly, Jianhua Liu and Christian Bernhard

Metals 2017, 7(11), 460; https://doi.org/10.3390/met7110460 - 30 Oct 2017

Cited by 53 | Viewed by 7837

Abstract

The formation of nonmetallic inclusions in the solidification process can essentially influence the properties of steels. Computational simulation provides an effective and valuable method to study the process due to the difficulty of online investigation. This paper reviews the modeling work of inclusion [...] Read more.

The formation of nonmetallic inclusions in the solidification process can essentially influence the properties of steels. Computational simulation provides an effective and valuable method to study the process due to the difficulty of online investigation. This paper reviews the modeling work of inclusion formation during the solidification of steel. Microsegregation and inclusion formation thermodynamics and kinetics are first introduced, which are the fundamentals to simulate the phenomenon in the solidification process. Next, the thermodynamic and kinetic models coupled with microsegregation dedicated to inclusion formation are briefly described and summarized before the development and future expectations are discussed. Full article

(This article belongs to the Special Issue Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals)

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