Segregation Patterns and the Phase-Field 3D-Model for Adiabatic Phase Transition in Al-Cu Alloys

2013 ◽  
Vol 668 ◽  
pp. 870-874
Author(s):  
Heng Min Ding ◽  
Tie Qiao Zhang ◽  
Lv Chun Pu
Keyword(s):  
Dendritic Growth ◽  
3D Model ◽  
Three Dimensional ◽  
Cartesian Grid ◽  
Solute Diffusion ◽  
Solute Redistribution ◽  
Cu Alloys ◽  
Solid Phases ◽  
Solid Liquid ◽  
Liquid And Solid Phases

In the paper, a model basing on solute conservative in every unit is developed for solving the solute diffusion equation during solidification. The model includes time-dependent calculations for temperature distribution, solute redistribution in the liquid and solid phases. Three-dimensional computations are performed for Al-Cu dendritic growth into an adiabatic and highly supersaturated liquid phase. A numerical algorithm was developed to explicitly track the sharp solid/liquid (S/L) interface on a fixed Cartesian grid. Three-dimensional mesoscopic calculations were performed to simulate the evolution of equiaxed dendritic morphologies.

3D Stochastic Modeling of Columnar-to-Equiaxed Transition During the Solidification of Alloy 718

2014 ◽  
Author(s):  
Laurentiu Nastac ◽  
Daojie Zhang
Keyword(s):  
Stochastic Modeling ◽  
3D Model ◽  
Three Dimensional ◽  
Alloy 718 ◽  
Solute Redistribution ◽  
Cpu Time ◽  
Growth Anisotropy ◽  
Columnar To Equiaxed Transition ◽  
2D And 3D ◽  
Liquid And Solid Phases

An efficient three-dimensional (3D) stochastic model for simulating the evolution of dendritic crystals during the solidification of alloys was developed. The model includes time-dependent computations for temperature distribution, solute redistribution in the liquid and solid phases, curvature, and growth anisotropy. The 3D model can run on PCs with reasonable amount of RAM and CPU time and therefore no parallel computations are needed. 3D mesoscopic computations at the dendrite tip length scale were performed in this study to simulate the formation of the columnar-to-equiaxed transition in alloy 718. Comparisons between microstructure predictions obtained via 2D and 3D stochastic modeling are also presented.

Analysis of Melting in a Mixed Metal Powder Bed With Finite Thickness Subjected to Constant Heat Flux Heating

2003 ◽  
Author(s):  
Tiebing Chen ◽  
Yuwen Zhang
Keyword(s):  
Selective Laser Sintering ◽  
Finite Thickness ◽  
Three Dimensional ◽  
Constant Heat Flux ◽  
Metal Powders ◽  
Powder Bed ◽  
Solid Foundation ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Liquid And Solid Phases

Melting of a subcooled powder bed with the finite thickness that contains a mixture of two metal powders with significantly different melting points is investigated analytically. Shrinkage induced by melting is taken into account in the physical model. The temperature distributions in the liquid and solid phases were obtained using an exact solution and an integral approximate solution, respectively. The effects of porosity, Stefan number, and subcooling on the surface temperature and solid-liquid interface are also investigated. The present work built solid foundation to investigate the complex three-dimensional selective laser sintering (SLS) process.

On the finite-amplitude steady convection in rotating mushy layers

2001 ◽  
Vol 437 ◽  
pp. 337-365 ◽  
Author(s):  
PETER GUBA
Keyword(s):  
Three Dimensional ◽  
Finite Amplitude ◽  
Taylor Number ◽  
Mushy Layer ◽  
Hexagonal Symmetry ◽  
Uniform Rotation ◽  
Mushy Layers ◽  
Solid Phases ◽  
Steady Convection ◽  
Liquid And Solid Phases

This study concentrates on a relatively simple model of a mushy layer originally proposed by Amberg & Homsy (1993) and later studied in further detail by Anderson & Worster (1995). We extend this model to the case in which the system is in a state of uniform rotation about the vertical. Of particular interest is to determine how the rotation of the system controls the bifurcating convection with both the oblique-roll planform and the planform of hexagonal symmetry. We find that two-dimensional oblique rolls can be either subcritically or supercritically bifurcating, depending on a pair of parameters (K1/CS, [Tscr ]), where K1 measures how the permeability linearly varies with the local solid fraction, CS relates the compositional difference between the liquid and solid phases to the variation of composition throughout the mushy layer, and the Taylor number [Tscr ] gives a measure of the local Coriolis acceleration relative to the viscous dissipation in a porous medium. The three-dimensional convection with hexagonal symmetry is found to be transcritical. Furthermore, distorted hexagons with upflow at the centres can be either subcritical or supercritical, depending on the value of the Taylor number [Tscr ].

scholarly journals Solid-liquid phase equilibria in the ternary systems H2O+ZnCl2+NaCl at temperatures of 298, 313 and 333 K

2021 ◽  
pp. 53-53
Author(s):  
Sevilay Demirci ◽  
Vedat Adiguze ◽  
Omer Sahin
Keyword(s):  
Liquid Phase ◽  
Phase Equilibria ◽  
Solid Phase ◽  
Ternary Systems ◽  
Viscosity Data ◽  
Isothermal Method ◽  
Chloride Water ◽  
Solid Phases ◽  
Solid Liquid ◽  
Liquid And Solid Phases

In this study, an economic separation method was suggested with the use of phase equilibria in order to ensure the recycling of ZnCl2 whose industrial waste amount is very high and to prevent it to form an environmental pollution. Sodium chloride-zinc chloride-water systems were examined with the isothermal method at temperatures of 298, 313 and 333 K. The analyses of the liquid and solid phases were used to determine the composition of the solid phase using the Schreinemakers graphic method. The solid-liquid phase equilibrium and viscosity data belonging to all ternary systems were identified and the solubility and viscosity changes with temperature were compared. The viscosity values were inversely proportional to the temperature as the amount of ZnCl2 in the solution increased. NaCl, 2NaCl ZnCl2 nH2O (n: 2, 0), ZnCl2 salts were observed at 298, 313, 333 K in the solid phases which are at equilibrium with the liquid phase at the invariant point.

Determination of the Position of Solid/Liquid Interface During Solidification and Melting of Metals With Vibrational Parameters

1993 ◽  
Author(s):  
Wang Fengquan ◽  
Zhu Zhenghua ◽  
Chen Shiyu
Keyword(s):  
Mechanical Model ◽  
Liquid Interface ◽  
Shear Stresses ◽  
Dynamical Equations ◽  
Solid Phases ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
First Time ◽  
Liquid And Solid Phases

Abstract The paper proposes the method to locate the solid / liquid interface with vibrational parameters during solidification for the first time. The sufficient difference in resistance to shear stresses between liquid and solid phases of metals and alloys permits the application of vibrational parameters to locate the interface in real time and in situation during solidification. Based on the solidification theory, continuum mechanics, vibrational modal analysis and sensitivity analysis, the author established the mechanical model and the dynamical equations of typical Bridgman solidifying system, derived the sensitivity of eigenvalues of the Bridgman system to the location of the solid / liquid interface as well as the calculating formulae concerned. The experimental results are quite accordant with those of computed ones.

scholarly journals Numerical Simulation of Three-Dimensional Dendrite Movement Based on the CA–LBM Method

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1056
Author(s):  
Qi Wang ◽  
Yingming Wang ◽  
Shijie Zhang ◽  
Binxu Guo ◽  
Chenyu Li ◽  
...  
Keyword(s):  
3D Model ◽  
Three Dimensional ◽  
Solidification Process ◽  
Movement Direction ◽  
Liquid Boundary ◽  
Alloy Microstructure ◽  
The Difference ◽  
Boltzmann Method ◽  
Solid Liquid ◽  
2D Model

At present, the calculation of three-dimensional (3D) dendrite motion using the cellular automata (CA) method is still in its infancy. In this paper, a 3D dendrite motion model is constructed. The heat, mass, and momentum transfer process in the solidification process of the alloy melt are calculated using a 3D Lattice–Boltzmann method (LBM). The growth process for the alloy microstructure is calculated using the CA method. The interactions between dendrites and the melt are assessed using the Ladd method. The solid–liquid boundary of the solute field in the movement process is assessed using the solute extrapolation method. The translational velocity of the equiaxed crystals in motion is calculated using the classical mechanical law. The rationality of the model is verified and the movement of single and multiple 3D equiaxed crystals is simulated. Additionally, the difference between 3D dendrite movement and two-dimensional (2D) dendrite movement is analyzed. The results demonstrate that the growth of moving dendrites is asymmetric. The growth velocity and falling velocity of the dendrite in the 3D model are faster than that in 2D model, while the simulation result is more realistic than that of the 2D model. When multiple dendrites move, the movement direction of the dendrites will change due to the merging of flow fields and other factors.

Solute redistribution during in-situ irradiation of alloys in the high voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 370-371
Author(s):  
P. R. Okamoto ◽  
N.Q. Lam ◽  
R. L. Lyles
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
Driving Forces ◽  
Solute Diffusion ◽  
Solute Redistribution ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Thin Foils ◽  
Solute Atoms

During irradiation of thin foils in a high voltage electron microscope (HVEM) defect gradients will be set up between the foil surfaces and interior. In alloys defect gradients provide additional driving forces for solute diffusion since any preferential binding and/or exchange between solute atoms and mobile defects will couple a net flux of solute atoms to the defect fluxes. Thus, during irradiation large nonequilibrium compositional gradients can be produced near the foil surfaces in initially homogeneous alloys. A system of coupled reaction-rate and diffusion equations describing the build up of mobile defects and solute redistribution in thin foils and in a semi-infinite medium under charged-particle irradiation has been formulated. Spatially uniform and nonuniform damage production rates have been used to model solute segregation under electron and ion irradiation conditions.An example calculation showing the time evolution of the solute concentration in a 2000 Å thick foil during electron irradiation is shown in Fig. 1.

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