Academic literature on the topic 'Solutal melting'
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Journal articles on the topic "Solutal melting":
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Mergui, S., and D. Gobin. "Transient Double Diffusive Convection in a Vertical Enclosure With Asymmetrical Boundary Conditions." Journal of Heat Transfer 122, no. 3 (April 11, 2000): 598–601. http://dx.doi.org/10.1115/1.1286673.
Abstract:
This study deals with the numerical analysis of transient heat and species transfer by natural convection in a binary fluid vertical layer. The cavity is differentially heated and a solutal buoyancy force is created by imposing a concentration step at one vertical wall: This refers to the experimental situation where the composition gradient inducing the solutal buoyancy force is created by melting of pure ice in a salty solution. The constitution of the flow structure and the time evolution of the heat and mass transfer characteristics are studied for opposing body forces over a range of thermal and solutal Rayleigh numbers. The numerical results allow to provide a better insight into the mechanisms driving the heat and species transfer at high Lewis number thermohaline convection. [S0022-1481(00)00303-0]
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Wells, Andrew J., and M. Grae Worster. "Melting and dissolving of a vertical solid surface with laminar compositional convection." Journal of Fluid Mechanics 687 (October 6, 2011): 118–40. http://dx.doi.org/10.1017/jfm.2011.322.
Abstract:
AbstractWe consider laminar compositional convection of buoyant melt released by ablation of a vertical solid surface into a two-component fluid. Asymptotic solutions are used to describe separate cases: the ablation rate is either controlled by thermal transport, corresponding to melting, or by solutal transport, corresponding to dissolution. Melting is faster and generates a stronger flow than dissolving. We determine the temperature and solute concentration conditions leading to either melting or dissolving and find that these conditions do not vary with the strength of the buoyancy that drives convective flow.
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Rettenmayr, Markus, and Martin Buchmann. "Solidification and Melting – Asymmetries and Consequences." Materials Science Forum 508 (March 2006): 205–10. http://dx.doi.org/10.4028/www.scientific.net/msf.508.205.
Abstract:
Solidification and melting are phase transitions from the liquid to solid state or vice versa and are thus often assumed to be similar processes with only opposite direction. However, they can be fundamentally different, i.e. asymmetric, in aspects of both thermodynamics and kinetics. It is known that superheat in the solid is difficult to obtain, unlike supercooling in the liquid. This is often attributed to the fact that nucleation in the liquid can occur (homogeneously or heterogeneously) in the bulk, in the solid it will occur at outer or inner surfaces of the crystal. A further asymmetry is evident as the growing phase is a phase with fast diffusion kinetics in the case of melting, with slow diffusion kinetics in the case of solidification. Two types of experiments (solutal melting and melting/resolidification in a temperature gradient) are presented that allow an evaluation and quantification of the consequences of these asymmetries.
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Ren, Neng, Jun Li, Chinnapat Panwisawas, Mingxu Xia, Hongbiao Dong, and Jianguo Li. "Simulation of the solute transport and microstructure evolution during the selective laser melting process." IOP Conference Series: Materials Science and Engineering 1281, no. 1 (May 1, 2023): 012003. http://dx.doi.org/10.1088/1757-899x/1281/1/012003.
Abstract:
Abstract Selective laser melting is of great expectation to be used in additive manufacturing of aerospace components with complex geometry. However, there are still defects in the built parts, such as solutal segregation and unexpected microstructure, which contribute to cracks and lead to failure. At present, most of the simulations focus on the macroscopic grain structure, and the solute transport process has not been well demonstrated yet. In the present work, we develop a two-way fully coupled model based on cellular automaton and finite volume method to simulate the solute transport and dendritic structure evolution during the melting and solidification of the SLM process. The results reveal the microstructural evolution and solute transport during the melting, spreading, and smearing of the powder. The proposed model framework shows good potential to be applied to further numerical investigation on the solidification behaviours of the SLM process.
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S. Idowu, A., and J. O. Olabode. "Dynamics of Heat Generating Upper-Convected Maxwell Fluid in a Porous Medium Over Melting Stretching Sheet with Stratification." Journal of Applied Science, Information and Computing 2, no. 1 (June 2, 2021): 12–23. http://dx.doi.org/10.59568/jasic-2021-2-1-03.
Abstract:
The flow of heat-generating Upper-Convected Maxwell (UCM) fluid in a porous medium over a melting stretching sheet with stratification is studied. The effects of viscous dissipation, magnetic field, heat generation/absorption, and stratification were considered on velocity, temperature, and concentration. The momentum, energy, and mass distribution models governing the fluid flow are solved numerically via the Spectral Collocation Method. The effects of various pertinent parameters on velocity, temperature, and concentration profiles were presented in graphs and tables. The results reveal that the heat-generating parameter, Eckert number, solutal, and thermal Grashof numbers heighten the velocity field. The temperature of the fluid is geared up with the variational increase in Eckert number and heat-generating parameter. Also, the heat absorption parameter and Eckert number reduce the temperature and concentration boundary layers accordingly.
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Deillon, L., J. Zollinger, D. Daloz, M. Založnik, and H. Combeau. "In-situ observations of solutal melting using laser scanning confocal microscopy: The Cu/Ni model system." Materials Characterization 97 (November 2014): 125–31. http://dx.doi.org/10.1016/j.matchar.2014.09.004.
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Ghoneim, A. "A meshfree interface-finite element method for modelling isothermal solutal melting and solidification in binary systems." Finite Elements in Analysis and Design 95 (March 2015): 20–41. http://dx.doi.org/10.1016/j.finel.2014.10.002.
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Shayesteh, G., A. Ludwig, M. Stefan-Kharicha, M. Wu, and A. Kharicha. "On the conditions for the occurrence of crystal avalanches during alloy solidification." Journal of Physics: Conference Series 2766, no. 1 (May 1, 2024): 012199. http://dx.doi.org/10.1088/1742-6596/2766/1/012199.
Abstract:
Abstract Experimental studies on the solidification of ammonium-chloride-water alloys in relatively large containments reveal conditions that lead to the formation of numerous crystal avalanches. Columnar segments that occasionally slide downwards along a vertical mushy zone further fragmentate and so crystal multiplication occurs. As a condition for this phenomenon solidification-induced solutal buoyancy that leads to a rising interdendritic flow was identified for the present case. The interaction with sedimentation-induced downward flow ahead of a vertical columnar region results in a redirection of the interdendritic flow and thus, to local conditions that slow down further solidification or even lead to remelting. Gravity is then pulling loose segments downwards. In larger containment, the flow in the bulk melt is generally unsteady and even turbulent. Thus, the outlined flow-solidification/melting interplay happens frequently at numerous positions but in a stochastic manner.
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Mishra, S. R., and Priya Mathur. "Williamson nanofluid flow through porous medium in the presence of melting heat transfer boundary condition: semi-analytical approach." Multidiscipline Modeling in Materials and Structures 17, no. 1 (May 19, 2020): 19–33. http://dx.doi.org/10.1108/mmms-12-2019-0225.
Abstract:
PurposePresent investigation based on the flow of electrically conducting Williamson nanofluid embedded in a porous medium past a linearly horizontal stretching sheet. In addition to that, the combined effect of thermophoresis, Brownian motion, thermal radiation and chemical reaction is considered in both energy and solutal transfer equation, respectively.Design/methodology/approachWith suitable choice of nondimensional variables the governing equations for the velocity, temperature, species concentration fields, as well as rate shear stress at the plate, rate of heat and mass transfer are expressed in the nondimensional form. These transformed coupled nonlinear differential equations are solved semi-analytically using variation parameter method.FindingsThe behavior of characterizing parameters such as magnetic parameter, melting parameter, porous matrix, Brownian motion, thermophoretic parameter, radiation, Lewis number and chemical particular case present result validates with earlier established results and found to be in good agreement. Finally reaction parameter is demonstrated via graphs and numerical results are presented in tabular form.Originality/valueThe said work is an original work of the authors.
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Simpson, James E., Suresh V. Garimella, Henry C. de Groh, and Reza Abbaschian. "Bridgman Crystal Growth of an Alloy With Thermosolutal Convection Under Microgravity Conditions." Journal of Heat Transfer 123, no. 5 (March 13, 2001): 990–98. http://dx.doi.org/10.1115/1.1389058.
Abstract:
The solidification of a dilute alloy (bismuth-tin) under Bridgman crystal growth conditions is investigated. Computations are performed in two dimensions with a uniform grid. The simulation includes the species concentration, temperature and flow fields, as well as conduction in the ampoule. Fully transient simulations have been performed, with no simplifying steady state approximations. Results are obtained under microgravity conditions for pure bismuth, and for Bi-0.1 at.% Sn and Bi-1.0 at.% Sn alloys, and compared with experimental results obtained from crystals grown in the microgravity environment of space. For the Bi-1.0 at.% Sn case the results indicate that a secondary convective cell, driven by solutal gradients, forms near the interface. The magnitude of the velocities in this cell increases with time, causing increasing solute segregation at the solid/liquid interface. Finally, a comparison between model predictions and results obtained from a space experiment is reported. The concentration-dependence of the alloy melting temperature is incorporated in the model for this case. Satisfactory correspondence is obtained between the predicted and experimental results in terms of solute concentrations in the solidified crystal.
Dissertations / Theses on the topic "Solutal melting":
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Abdedou, Nazim. "Non-equilibrium conditions at solid/liquid interfaces." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0346.
Abstract:
Notre travail porte sur la fusion dite solutale survenant lorsque l'on met deux métaux en contact à une température comprise entre leurs températures de fusion respectives. L'interface solide/liquide se retrouve initialement fortement hors-équilibre et la cinétique propre à son retour à l'équilibre semble mettre en défaut les modèles généralement employés pour décrire la solidification et la fusion. Pour progresser dans la compréhension du processus, nous avons abordé le problème sous trois angles complémentaires. Dans un premier temps, nous avons réalisé des expériences in-situ de fusion solutale du système Au-Ag en utilisant la tomographie par rayons X. L'analyse critique des résultats semble montrer que l'interface solide-liquide reste hors équilibre pendant la fusion solutale, avec la persistance inattendue de gradients de concentration à la fin des expériences. Dans un deuxième temps, dans le but de mieux comprendre les expériences, nous avons mis en œuvre un modèle reposant sur la thermodynamique des processus irréversibles appliquée aux échanges d'espèces chimiques à travers une interface solide/liquide abrupte. Une paramétrisation des coefficients de transfert interfaciaux permet au modèle de reproduire qualitativement les comportements observés dans les expériences. Enfin, nous avons cherché à justifier les paramètres cinétiques du modèle thermodynamique en utilisant la dynamique moléculaire (DM) dans le système Cu-Ni. Nous avons ainsi démontré que les coefficients interfaciaux dépendent des concentrations à l'interface, en accord avec la paramétrisation du modèle thermodynamiqueOur work focuses on solutal melting, which occurs when two metals are brought into contact at a temperature between their respective melting temperatures. The solid/liquid interface is initially far from equilibrium, and the kinetics governing its return to equilibrium appear to challenge the models commonly used to describe solidification and melting. To advance our understanding of the process, we approached the problem from three complementary angles. First, we conducted in-situ experiments on the solutal melting of the Au-Ag system using X-ray tomography. Critical analysis of the results appears to indicate that the solid-liquid interface remains out of equilibrium during solutal melting, with the unexpected persistence of concentration gradients at the end of the experiments. Second, in an effort to better understand the experiments, we developed a model based on the thermodynamics of irreversible processes applied to the exchange of chemical species across a sharp solid/liquid interface. Parametrization of interfacial transfer coefficients enables the model to qualitatively reproduce the behaviors observed in the experiments. Finally, we sought to justify the kinetic parameters of the thermodynamic model using molecular dynamics (MD) in the Cu-Ni system. We thus demonstrated that the interfacial coefficients depend on the concentrations at the interface, consistent with the parametrization of the thermodynamic model
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Yasensky, David. "Solute-driven melting kinetics in the Sn-Bi system." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015847.
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Harrington, Robert Franklin 1955. "Release of meltwater and ionic solute from melting snow." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/191224.
Abstract:
The release of ionic solute from melting seasonal snow produces an influx of ion laden water into hydrologic systems at the start of spring snowmelt. The spatial and temporal variability of meltwater and solute release from melting snow was investigated at different spatial scales to assess the magnitude and variability of this process. Four laboratory experiments were performed where an 0.4 m³ volume of snow was placed in a plexiglass box and melted from above. NaCl and dye tracer experiments revealed contemporaneous areas of concentrated dye and dilute meltwater in flow fingers, indicating that meltwater in preferential flow paths is diluted by low concentration water from the top of the snowpack. Meltwater discharge and meltwater electrical conductivity were measured in snow lysimeters, and snow accumulation and electrical conductivity of samples from snowpits were measured over four snowmelt seasons at an alpine field site. Peak snow-water equivalent ranged from 0.57 to 2.92 m, and lysimeter discharges ranged from 20 to 205% of the mean flow; however mean lysimeter flow was representative of snow ablation observed in snow pits. The electrical conductivity in snowpit samples and lysimeter meltwater averaged 2-3 μS cm⁻¹. Peak meltwater electrical conductivity ranged from 6 to 14 times that of the bulk premelt snowpack. The highest conductivities were observed during the first few days following the onset of flow, and the lysimeters that began flowing earliest tended to have the highest conductivities at the onset of flow. A mathematical model for solute transport in snow was developed that includes the effects of mass transfer between mobile and immobile liquid phases, advection, hydrodynamic dispersion, and melt—freeze episodes. The ability of the model to accurately simulate solute movement and release depends on the validity of the assumption of one—dimensional flow and on the accuracy of modeling the snowpack energy balance. This model is preferable to the empirical models of solute elution currently in use for investigations of watershed hydrogeochemical response because it has the ability to respond directly to changes in snow accumulation or meteorlogical conditions.
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Vasudevamurthy, Madhusudan. "Betaine analogues and related compounds for biomedical applications." Thesis, University of Canterbury. Chemical and Process Engineering, 2006. http://hdl.handle.net/10092/1096.
Abstract:
Living cells accumulate compensatory solutes for protection against the harmful effects of extreme environmental conditions such as high salinity, temperature and desiccation. Even at high concentrations these solutes do not disrupt the normal cellular functions and at times counteract by stabilizing the cellular components. These properties of compensatory solutes have been exploited for stabilizing proteins and cells in vitro. Betaines are widespread natural compensatory solutes that have also been used in other applications such as therapeutic agents and polymerase chain reaction (PCR) enhancers. Some biomedical applications of novel synthetic analogues of natural betaines were investigated. Natural compensatory solutes are either dipolar zwitterionic compounds or polyhydroxyl compounds, and the physical basis of compensation may differ between these, so one focus was on synthetic betaines with hydroxyl substituents. The majority of the synthetic solutes stabilized different model proteins against stress factors such as high and low temperatures. The presence of hydroxyl groups improved protection against desiccation. The observed stabilization effect is not just on the catalytic activity of the enzyme, but also on its structural conformation. Synthetic compensatory solutes have a potential application as protein stabilizers. Dimethylthetin was evaluated as a therapeutic agent and found to be harmful in a sheep model. However, from the study we were able to generate a large-animal continuous ambulatory peritoneal dialysis (CAPD) model and showed that glycine betaine could be added to the dialysis fluid in chronic renal failure. Some synthetic compensatory solutes reduce the melting temperatures of DNA better than most natural solutes. Synthetic solutes were identified that have potential to enhance PCR and could replace some reagents marketed by commercial suppliers. Density, viscosity and molecular model data on the solutes showed correlations with the biochemical effects of the solutes, but no physical measurements were found that reliably predicted their potential for biotechnological applications.
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Harrington, Robert Franklin. "Release of meltwater and ionic solute from melting snow." 1997. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1997_97_sip1_w.pdf&type=application/pdf.
Book chapters on the topic "Solutal melting":
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"Physicochemical Properties of Organic Compounds and Drug Molecules." In Basic Chemistry for Life Science Students and Professionals, 315–66. The Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/9781839168086-00315.
Abstract:
This chapter summarises the International System of Units (SI Units) applicable to the analysis of organic compounds and drug molecules. By using practical examples and problem-solving exercises, units of measurements including length, mass, temperature, time, volume, and density, and calculations based on moles (e.g. mole fraction, mole percentage, molality, molarity, and normality) are included. The solubility of organic compounds is reviewed by defining parameters such as solutes, solvents, solvation and dissolution, and other physical property measurements such as boiling point, density, and melting point. Underpinning topics outlined in the various chapters, acid–base properties with definitions, principles and applications in chemical measurements, and common reactions of organic compounds are scrutinised.
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Dhariwal, Jyoti, Gaurav Choudhary, Dipti Vaya, Srikanta Sahu, Manish Shandilya, Poonam Kaswan, Ambrish Kumar, Shruti Trivedi, Manoj K. Banjare, and Kamalakanta Behera. "Self-Assembled Nanostructures within Ionic Liquids-based Media." In Ionic Liquids: Eco-friendly Substitutes for Surface and Interface Applications, 111–59. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9789815136234123010011.
Abstract:
Ionic liquids (ILs) have shown immense potential as suitable alternatives to environmentally damaging volatile organic solvents (VOS). These unique materials possess very unusual physicochemical properties, such as low melting point, high boiling point, excellent thermal and chemical stability, large electrochemical window, very low volatility and high conductivity. One of the most important features associated with ILs is that their physicochemical properties, like viscosity, density, hydrophobicity, solubility, polarity, etc., can be effectively tuned for desired applications just by tuning the structures of cations and/or anions. Further, these designer solvents show dual behavior, i.e., electrolytes and solvents. In the last two decades, these unique materials have shown tremendous application potential in various interdisciplinary research areas, such as synthesis, catalysis, separation, extraction, nanoscience, and pharmaceutics, among many others. Further, the formation of surfactant self-assembled nanostructures (micelles and microemulsions (ME)) within ionic liquid-based systems of immense importance due to the vast utility of these nanostructures well as ILs in various fields of science and technology. These microheterogeneous systems can be effectively used as greener alternatives to those environmentally harmful volatile organic solvents which are largely used for academic and industrial research purposes.atile organic solvents which are largely used for academic and industrial research purposes. The IL-based self-assembled nanostructures show major advantages due to their affinity to solubilize many chemical and biochemical solutes (both hydrophilic as well as hydrophobic), thereby expanding their potential application as solubilizing media, media for synthesis, catalysis and biocatalysis, separation and extraction, drug delivery vehicles, and media for biochemical stability (e.g., protein and enzyme stability). This book chapter will highlight the formation and utility of various types of self-assembled nanostructures formed by surfactants, polymers, etc., within Ils-based media.
Conference papers on the topic "Solutal melting":
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DeZego, Shawn E., W. Kinzy Jones, Z. F. Dong, and M. A. Ebadian. "Experimental Study of the Effects of Thermal and Solutal Convections in the Continuous Cast of a Binary Mixture." In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0084.
Abstract:
Abstract An experimental study of the solidification process for the continuous cast of a binary NH4CI-H2O solution with varying inlet temperature and composition has been performed. Thermal and solutal density gradients have been found to strongly affect flow in the liquid region and are mainly responsible for the redistribution of species on the macroscopic scale. Flow visualizations have shown that dense solute-rich solution, rejected from the mushy zone, was redistributed into the upper regions of the liquid melt during cases of hypoeutectic initial concentrations. Localized remelting and shearing of columnar dendritic growth for the hypoeutectic cases and the redistribution and melting of equiaxed dendritic growth for the hypereutectic cases have also been found to strongly depend on the solution inlet temperature. It was established that the extent of equiaxed free solid that accumulated in the lower region of the liquid melt for the hypereutectic cases was dependent on the initial solution composition. Concentration histories show that segregation of species along the vertical centerline in the liquid pool have been measured to be in excess of 4% for some cases during quasisteady conditions. The warm buoyant solution entering the liquid melt via the feeding nozzle significantly increased convective effects that were not detected in previous research on static test sumps.
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Jiang, J., and Y. X. Tao. "Interaction Coefficient Between Ice Particles in Convective Melting of Granular Packed Bed." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-1032.
Abstract:
Abstract To numerically simulate the convective melting of packed bed it is necessary to determine the thermophysical properties or their constitutive equations. One of the most uncertain values among them is the solute interaction coefficient of solid particles, which represents the interaction force between solid particles and is equivalent to the viscosity term in Navier-Stokes equations if the dirty fluid model is applied. It was found from the previous study that the solute (solid particle) interaction coefficient, μs, characterizes the solubility such as the melting rate, the distribution of ice volume fraction, the velocity of ice particle, and the melting time. In this study, a parametric study based on the two-dimensional model for the convective melting of granular packed beds (Jiang et al. 1999) is conducted to determine the sensitivity of interaction coefficient to the model prediction. The packed bed considered here is collection of ice particles of various shapes. Warm water at a constant temperature enters horizontally the bed where melting takes place. Two cases are considered. One is to consider μs as constant, and the other is to consider it as a function of the ice volume fraction. The melting rate, fluid flow velocity and ice volume fraction distribution are discussed for different interaction coefficient values. An “optimal” interaction coefficient between ice particles is determined by comparing the simulation data with experimental data (Tao et al. 1998). It is found that the melting results are most sensitive to the value of constant interaction coefficient rather than to whether it is a constant or as a function of the ice volume fraction.
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Liu, Dehao, and Yan Wang. "Simulation of Nucleation and Grain Growth in Selective Laser Melting of Ti-6Al-4V Alloy." In ASME 2019 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/detc2019-97684.
Abstract:
Abstract Selective laser melting (SLM) builds parts by selectively melting metallic powders layer by layer with a high-energy laser beam. It has a variety of applications in aerospace, medical device, and other low-volume manufacturing. Nevertheless, the lack of fundamental understanding of the process-structure-property (P-S-P) relationship for better quality control inhibits wider applications of SLM. Recently, a mesoscale simulation approach, called phase-field and thermal lattice Boltzmann method (PF-TLBM), was developed to simulate microstructure evolution of alloys in SLM melt pool with simultaneous consideration of solute transport, heat transfer, phase transition, and latent heat effect. In this paper, a nucleation model is introduced in the PF-TLBM model to simulate heterogeneous nucleation at the boundary of melt pool in SLM. A new method is also developed to estimate the thermal flux out of the SLM melt pool model given a constant cooling rate. The effects of latent heat and cooling rate on dendritic morphology and solute distribution are studied. The simulation results of Ti-6Al-4V alloy suggest that the inclusion of latent heat is necessary because it reveals the details of the formation of secondary arms, reduces overestimated microsegregation, and provides more accurate kinetics of dendritic growth.
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Xu, L. S., and Y. G. Shan. "Modeling the Influence of Solution Properties on Precipitations of Vaporizing Droplets in Plasma Gases." In ITSC2013, edited by R. S. Lima, A. Agarwal, M. M. Hyland, Y. C. Lau, G. Mauer, A. McDonald, and F. L. Toma. ASM International, 2013. http://dx.doi.org/10.31399/asm.cp.itsc2013p0648.
Abstract:
Abstract Solution droplets injected into a plasma jet experience a sequence of thermal, physical, and chemical processes. These include droplet breakup and collisions, solvent vaporization, solute precipitation and pyrolysis, formation of the product particles, sintering, and perhaps melting. Depending on plasma conditions, solution concentration, and the properties of the solvent and solute, different particle morphologies are produced. In this paper, a heat and mass transfer model for vaporizing solution droplets was used to investigate the influence of solvent type, initial salt content, and concentration. Temperature and composition dependent thermo-physical properties were used. Temperature and concentration distributions and variations of precursor droplets (cerous nitrate and zirconia acetate in water and ethanol) were predicted.
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Maloney, Thad C., and Hannu Paulapuro. "Thermoporosimetry of Pulp Fibers." In The Science of Papermaking, edited by C. F. Baker. Fundamental Research Committee (FRC), Manchester, 2001. http://dx.doi.org/10.15376/frc.2001.2.897.
Abstract:
This paper covers the use of thermoporosimetry to measure the pore size distribution (PSD) of pulp fibers. Thermoporosimetry is based on the melting temperature depression of an absorbate in a porous structure. A discreet or “step” melting procedure, rather than the usual continuous method, is used to melt the absorbate. This method eliminates thermal lag and gives the high temperature accuracy required for measuring large pores. Measurement of water-saturated chemical pulp fibers using this technique, combined with solute exclusion, indicates a bimodal distribution of cell wall pores. The interpretation of data from water-saturated fibers is complicated by several factors: 1) distortion of the cell wall by ice crystal growth; 2) the depression of water’s melting temperature by osmotic pressure; and 3) inadequate range to cover the larges pores. One way to correct these problems is by replacing the water with cyclohexane. The major disadvantage of this approach is that the cell wall contracts in cyclohexane and its pore structure may change in other ways which are not understood. Like water, the cyclohexane analysis shows a bimodal distribution of pores. The smaller pores, “micropores”, are less than about 5 nm in diameter, the “macropores” are about 15–700 nm. It was found that there is a quantity of cyclohexane in the cell wall which does not freeze. Analysis of nonfreezing cyclohexane indicates a surface area of about 400 m2/g for kraft pulp. The cyclohexane method is very suitable for studying beating, which primarily involves the opening of larger pores.
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Gao, Michael C., Paul D. Jablonski, Jeffrey A. Hawk, and David E. Alman. "High-Entropy Alloys: Formation and Properties." In ASME 2018 Symposium on Elevated Temperature Application of Materials for Fossil, Nuclear, and Petrochemical Industries. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/etam2018-6732.
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This paper presents ongoing research at NETL aimed at gaining fundamental understanding of high-entropy alloys (HEAs) formation and their properties, and developing highperformance HEAs for high-temperature fossil energy applications. First-principles density functional theory (DFT), Monte Carlo simulation, and molecular dynamics simulation are carried out to predict enthalpy of formation, the entropy sources (i.e., configurational entropy, vibrational entropy, and electronic entropy), and elastic properties of model single-phase HEAs with the face-centered cubic, body-centered cubic and hexagonal closed-packed structures. Classical elastic theory, which considers the interactions between dislocations and elastic fields of solutes, has also been used to predict solid solution strengthening. Large-size (∼7.5 kg) HEAs ingots are produced using vacuum induction melting and electroslag remelting methods, followed by homogenization treatment resulting in greater than 99% homogeneity. Subsequent thermomechanical processing produces fully-wrought face-centered cubic microstructures. The tensile behavior for these alloys have been determined as a function of temperature, and based on these results screening creep tests have been performed at selected temperatures and stresses.
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Kazemi, Komeil, Andrei Artemev, Jianguo Zhou, and John A. Goldak. "A Macro-Micro Model of Fusion Zone Microstructure Evolution in Mn-C Low-Alloy Steel Coupled With Thermal Stress Analysis." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45994.
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A macro-micro-model for microstructure evolution in the fusion zone of a l.2 Mn and 0.11 C low-alloy steel is described. The macro-model is a 3D transient thermal analysis of a welded structure that resolves the weld pool with element size greater than 1 mm and time steps greater than 1 second. The micro-model has cell size of about 1 micron and time step size of about 10 micro-seconds with a grid of about 80×80×500 cells. The micro model is positioned on the liquid-solid interface of the weld pool in the macro-model. The boundary conditions for the micro-model are mapped from the macro-model. The micro-model solves the 3D transient solute diffusion equations for Mn and C. The micro-model computes the liquid-solid interface movement with local velocities determined by local temperature, compositions of solid and liquid phases and interface curvature to predict columnar or dendritic solidification structures. As the solid cools from the melting point to room temperature, the evolution of austenite, ferrite, pearlite, bainite and martensite phases are computed. The 3D transient stress due to temperature and phase changes is computed in the micro-model as it cools from the melting temperature to room temperature. At room temperature a micro-model tensile test is run to 4% strain. The macro-stress and strain is compared to the micro-stress and strain distributions. The model is intended to be used to initialize models of fracture, fatigue and creep in weld fusion zones.
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Fang, Haisheng, Lili Zheng, Hui Zhang, Yong Hong, and Qun Deng. "A Novel Method for Melt Flow Control and Inclusion Suppression in Optical Crystal Growth." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41581.
Abstract:
Optical and laser crystals grown by Czochralski technique from a solute-rich melt usually suffer defects of melt inclusion or bubble core, which severely affects optical, thermal and mechanical properties of the material. The main purpose of this paper is to study the inclusion mechanisms and to minimize such defects. Two types of mechanisms possibly responsible for inclusion defects are presented. In the current investigation, Czochralski grown optical single crystals are examined to recognize the effects of crystal rotation and natural convection on the melt flow pattern and solidification interface shape. It is established that increasing the rotation rate of crystal or reducing natural convection in the melt will cause the solid-liquid interface change from the convex shape to concave and high concentration of the species may be pushed away from the solidification interface. Simulations were performed to establish the relationships between Gr/Re2 and growth interface shape change, and between Gr/Re2 and stagnant point location were established. A disk submerged into the melt was used to reduce natural convection by reducing the melt height. The idea was similar to the submerged baffle or submerged heater used in Bridgeman crystal growth. The effect of submerged baffle on enhancement of crystal rotation effect was demonstrated. Simulation results showed that the melt flow near the solidification interface depended strongly on the baffle location, which was not surprised. The idea of submerged heater was also examined in Czochralski growth. Different from a constant temperature close to the melting temperature used in Bridgman growth, the submerged heater temperature should be selected on a higher temperature between the melting temperature and crucible temperature. The value depended strongly on the ratio between crystal and crucible diameters. It was proved that a constant temperature was not the best choice in Czochralski growth. In fact, an optimized temperature profile could be found in numerical simulations for melt flow control and inclusion suppression.
9
Wei, T. G., C. S. Long, B. F. Luan, Z. Miao, W. Wang, and L. Chen. "Microstructure and Performance of Zr-1.0Cr-0.4Fe-xMo Alloys." In 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-15920.
Abstract:
For the possibility to develop Zr-based alloys with good corrosion resistance and relatively high strength as well at elevated temperature, Zr-1.0Cr-0.4Fe-xMo (x = 0, 0.2, 0.4, 0.6) alloys with different Mo addition were studied. These alloys were prepared by vacuum arc melting, the microstructure, phase transformation, tensile strength, corrosion resistance and hydrogen uptake during corrosion of these alloys was studied and the effect of Mo addition was discussed. Mo addition had a refinement effect on the microstructure, the α-laths size of the alloys in as-cast condition was decreased by Mo addition, and the recrystal grains of the alloy with 0.6% Mo addition were several times smaller than those of the alloy with no Mo addition in general. Mo addition also affected the characteristics of the second phase particles (SPPs), with the increase of Mo content, the population density of the SPPs increased significantly, whereas the average diameter of the SPPs decreased. Mo addition had a stabilization effect on β phase, the/ (α+β) phase transition temperature decreased with Mo content, especially when Mo was added to the Mo free alloy. The tensile strength of Zr-1.0Cr-0.4Fe-xMo alloys was higher than that of Zr-1.0Sn-0.3Nb-0.3Fe-0.1Cr alloy at 350°C and tended to increase with Mo content. Zr-1.0Cr-0.4Fe-xMo alloys had excellent corrosion resistance in 500°C 10.3MPa steam due to the large number of fine SPPs in the matrix. Addition of Mo promoted the change of the oxidation from cubic kinetics to liner kinetics and the formation of cracks in the oxide layers. It was thought that the solute Mo atoms in Zr matrix played an important role on the degradation of corrosion resistance. Hydrogen uptake fraction of Zr-1.0Cr-0.4Fe-xMo alloys was high initially during corrosion and decreased with the exposure time in the pre-transition region, however, when cracks were formed in the oxide layers in pos-transition region, hydrogen uptake fraction of the alloys would reached to a high level again.
Reports on the topic "Solutal melting":
1
Chefetz, Benny, and Baoshan Xing. Sorption of hydrophobic pesticides to aliphatic components of soil organic matter. United States Department of Agriculture, 2003. http://dx.doi.org/10.32747/2003.7587241.bard.
Abstract:
Sorption of hydrophobic compounds to aliphatic components of soil organic matter (SOM) is poorly understood even though these aliphatic carbons are a major fraction of SOM. The main source of aliphatic compounds in SOM is above- and below-ground plant cuticular materials (cutin, cutan and suberin). As decomposition proceeds, these aliphatic moieties tend to accumulate in soils. Therefore, if we consider that cuticular material contributes significantly to SOM, we can hypothesize that the cuticular materials play an important role in the sorption processes of hydrophobic compounds (including pesticides) in soils, which has not yet been studied. The overall goal of this research was to illustrate the mechanism and significance of the refractory aliphatic structures of SOM in sorbing hydrophobic compounds (nonionic and weakly polar pesticides). The importance of this study is related to our ability to demonstrate the sorption relationship between key pesticides and an important fraction of SOM. The specific objectives of the project were: (1) To isolate and characterize cuticular fractions from selected plants; (2) To investigate the sorption mechanism of key hydrophobic pesticides and model compounds to cuticular plant materials; (3) To examine the sorption mechanisms at the molecular level using spectroscopic techniques; (4) To investigate the sorption of key hydrophobic pesticides to synthetic polymers; (5) To evaluate the content of cuticular materials in agricultural soils; and (6) To study the effect of incubation of plant cuticular materials in soils on their sorptive capabilities. This project demonstrates the markedly high sorption capacity of various plant cuticular fractions for hydrophobic organic compounds (HOCs) and polar organic pollutants. Both cutin (the main polymer of the cuticle) and cutan biopolymers exhibit high sorption capability even though both sorbents are highly aliphatic in nature. Sorption by plant cuticular matter occurs via hydrophobic interactions and H-bonding interactions with polar sorbates. The cutin biopolymer seems to facilitate reversible and noncompetitive sorption, probably due to its rubbery nature. On the other hand, the epicuticular waxes facilitate enhance desorption in a bi-solute system. These processes are possibly related to phase transition (melting) of the waxes that occur in the presence of high solute loading. Moreover, our data highlight the significance of polarity and accessibility of organic matter in the uptake of nonpolar and polar organic pollutants by regulating the compatibility of sorbate to sorbent. In summary, our data collected in the BARD project suggest that both cutin and cutan play important roles in the sorption of HOCs in soils; however, with decomposition the more condensed structure of the cutin and mainly the cutan biopolymer dominated sorption to the cuticle residues. Since cutin and cutan have been identified as part of SOM and humic substances, it is suggested that retention of HOCs in soils is also controlled by these aliphatic domains and not only by the aromaticrich fractions of SOM.