Modeling of Microstructure Evolution in Nb-Si Eutectic Alloy Using Cellular Automaton Method

2008 ◽  
Vol 1128 ◽  
Author(s):  
Kenichi Ohsasa ◽  
Seiji Miura
Keyword(s):  
Cellular Automaton ◽  
Microstructure Evolution ◽  
Eutectic Alloy ◽  
Eutectic Composition ◽  
Eutectic Growth ◽  
Liquid Interface ◽  
Dendrite Morphology ◽  
Cellular Automaton Method ◽  
Solid Liquid Interface ◽  
Solid Liquid

AbstractA numerical model was developed for the simulation of microstructure evolution during the solidification of Nb-Si eutectic alloy. In this model, the cellular automaton method was used to simulate the eutectic growth of Nb solid solution and Nb3Si intermetallics. Diffusion in liquid, mass conservation at the solid/liquid interface and local equilibrium at the solid/liquid interface with consideration of curvature undercooling were solved to determine the positions of the Nb/liquid and Nb3Si/liquid interfaces. In the alloy with eutectic composition of 0.18at%Nb, irregular eutectic growth morphology was observed in relatively lower undercooling region. On the other hand, in higher undercooling region over 50K, dendrite morphology of Nb3Si was observed. An alloy with hypo-eutectic composition, cell and dendrite morphology were observed in lower undercooling region, while coupling eutectic morphology was formed in higher undercooling region over 25K.The growth velocity of the coupling growth increased with increase in the degree of undercooling of melt.

Microstructure and Solid/Liquid Interface Evolutions of Directionally Solidified Fe-Al-Ta Eutectic Alloy

2019 ◽  
Vol 34 (3) ◽  
pp. 656-661 ◽  
Author(s):  
Chunjuan Cui ◽  
Songyuan Wang ◽  
Meng Yang ◽  
Haijun Su ◽  
Yagang Wen ◽  
...  
Keyword(s):  
Eutectic Alloy ◽  
Liquid Interface ◽  
Directionally Solidified ◽  
Solid Liquid Interface ◽  
Solid Liquid

Influence of initial solid–liquid interface morphology on further microstructure evolution during directional solidification

2012 ◽  
Vol 110 (2) ◽  
pp. 443-451 ◽  
Author(s):  
Dongmei Liu ◽  
Xinzhong Li ◽  
Yanqing Su ◽  
Jingjie Guo ◽  
Liangshun Luo ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Microstructure Evolution ◽  
Liquid Interface ◽  
Interface Morphology ◽  
Solid Liquid Interface ◽  
Solid Liquid

scholarly journals Numerical Analysis of Solidification Behavior during Laser Welding Nickel-based Single-crystal Superalloy Part IV: Optimization of Thermo-metallurgical Factors

2021 ◽  
Vol 1996 (1) ◽  
pp. 012004
Author(s):  
Zhiguo Gao
Keyword(s):  
Single Crystal ◽  
Welding Speed ◽  
Laser Power ◽  
Liquid Interface ◽  
Solidification Behavior ◽  
Dendrite Morphology ◽  
Grain Formation ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Stray Grain

Abstract Important metallurgical factors, such as alloying aluminum redistribution, supersaturation and undercooling of dendrite tip around solid/liquid interface, are separately optimized to alleviate stray grain formation and columnar/equiaxed transition (CET) with series of welding conditions and provide a very efficient method for microstructure control through modification of growth kinetics of dendrite tip under nonequilibrium solidification conditions of ternary Ni-Cr-Al molten pool. Asymmetrical (001)/[110] welding configuration is inferior to symmetrical (001)/[100] welding configuration, because overall area-weighted alloying redistribution, supersaturation and undercooling of dendrite tip throughout the solid/liquid interface of weld pool are consistently severer to exacerbate solidification behavior and microstructure development and incur morphology instability of columnar/equiaxed transition. High heat input, such as combination of higher laser power and slower welding speed, monotonically increases aluminum enrichment, supersaturation and undercooling of dendrite tip near solidification interface to simultaneously deteriorate nucleation and growth of stray grain formation and weaken columnar dendrite morphology, while low heat input, such as combination of lower laser power and faster welding speed, decreases solute buildup, relieves supersaturation and beneficially suppresses dendrite tip undercooling to minimize equiaxed dendrite morphology in the crack-susceptible region, and thereby facilitate single-crystal epitaxial growth with decrease of thermo-metallurgical factors for columnar/equiaxed transition in order to provide prerequisite for optimization of welding conditions. Favorable solidification conditions are obtainable with preferential crystallographic orientation to eliminate columnar/equiaxed transition under which the epitaxy of single-crystal metallurgical properties across fusion boundary of substrate is predominantly promoted to essentially reduce stray grain formation in (001)/[100] welding configuration, and is kinetically capable of significant reduction of microstructure anomalies and nonuniform solidification behavior. The useful relationship among welding conditions, alloying aluminum redistribution, supersaturation and undercooling of dendrite tip is properly established within dendrite stability range through thorough analysis. In addition, the validation of theoretical predictions is fairly reasonable by the experiment results. It is worth that the contributions of kinetics-related solidification phenomena with advancement of solid/liquid interface are imposed altogether to understand why stray grain formation occurs on the basis of controlling mechanism of minimum undercooling or minimum velocity by the reproducible methodology procedure.

Study on the Natural Convection and Formation of Periodic Diphase Dendrite in Al-La Alloys

2010 ◽  
Vol 129-131 ◽  
pp. 1308-1312
Author(s):  
Ya Hong Zheng ◽  
Yan Lin Wang ◽  
Zi Dong Wang
Keyword(s):  
Crystal Growth ◽  
Natural Convection ◽  
Concentration Distribution ◽  
Concentration Field ◽  
Growth Direction ◽  
Liquid Interface ◽  
Dendrite Morphology ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Interface Edge

In the crystal growth process, the temperature distribution and concentration distribution at the solid-liquid interface edge are always the hot problems. In this paper, we study the concentration distribution at the solid-liquid interface edge under the natural convection conditions, we find that the concentration field is oscillating exponential decline or rose along the crystal growth direction. We also study the dendrite morphology of Al-La alloys using the experimental method, the results show that the microstructure of Al-35%La alloys is different from the common microstructure of hypereutectic alloy during the conventional casting process, the first crystalline phase is Al11La3, which composition is discontinuous along the growth direction, the main dendrite is composed of α-Al alternating with Al11La3, the results of SEM and XRD show that the chemical composition along the main dendrite exhibits periodic behavior, therefore, this microstructure is named as periodic diphase dendrite structure.

A New Growth Kinetics in Simulation of Dendrite Growth by Cellular Automaton Method

2007 ◽  
Vol 26-28 ◽  
pp. 957-962 ◽  
Author(s):  
Bo Wei Shan ◽  
Xin Lin ◽  
Lei Wei ◽  
Wei Dong Huang
Keyword(s):  
Cellular Automaton ◽  
Growth Kinetics ◽  
Solute Concentration ◽  
Dendrite Growth ◽  
Liquid Interface ◽  
Interface Temperature ◽  
Algebraic Equations ◽  
Interface Growth ◽  
Solid Liquid Interface ◽  
Solid Liquid

A modified cellular automaton model was proposed to simulate the dendrite growth of alloy. Different from previous models, this model used neither an analytical equation(such as KGT model) nor an interface solute gradient equation to solve the velocity of solid-liquid interface, but used the interface solute and energy conservation and thermodynamic equilibrium condition to describe the solid/liquid interface growth kinetics process. In present model, once the temperature field and solute field were solved by finite different method in the entire domain, the material thermodynamic properties can be substituted into four algebraic equations to easily determine the variation of solid fraction, interface temperature and solute concentration, instead of calculating interface moving velocity. As a result, the complexity of the calculation can be largely reduced. The simulated dendrite growth was in a good agreement with the Lipton–Glicksman–Kurz (LGK) model for free dendritic growth in undercooled melts.

Formation of the Microstructure in a Rapid Directionally Solidified Immiscible Alloy

2006 ◽  
Vol 508 ◽  
pp. 31-36
Author(s):  
Jiu Zhou Zhao ◽  
Lorenz Ratke
Keyword(s):  
Microstructure Evolution ◽  
Phase Segregation ◽  
Liquid Interface ◽  
Solidification Velocity ◽  
Directionally Solidified ◽  
Diffusional Growth ◽  
Immiscible Alloy ◽  
Minority Phase ◽  
Solid Liquid Interface ◽  
Solid Liquid

A model has been developed by taking into account the common action of the nucleation, the diffusional growth, the collisions and coagulations of the minority phase droplets and the spatial phase segregation to describe the microstructure evolution in an immiscible alloy solidified rapidly under the vertical directional solidification conditions. The model is satisfactorily verified by comparison with an analytically solvable case first, and then applied to predict the microstructure evolution in a directionally solidified Al-Pb alloy. The numerical results show that at a high solidification velocity a constitutional supercooling region appears in front of the solid/liquid interface and the liquid-liquid decomposition takes place there. A higher solidification velocity leads to a higher nucleation rate for a given temperature gradient and, therefore, a higher number density of the minority phase droplets. As a result, the average radius of droplets in the melt at the solid/liquid interface decreases with the solidification velocity.

scholarly journals Evaluation of the solid/liquid interface undercooling during Sn-Se Eutectic growth

1998 ◽  
Vol 1 (1) ◽  
pp. 05-10 ◽  
Author(s):  
M. Zanotello ◽  
C.T. Rios ◽  
R.H.B. Jacon ◽  
R. Caram
Keyword(s):  
Eutectic Growth ◽  
Liquid Interface ◽  
Solid Liquid Interface ◽  
Solid Liquid

scholarly journals Concentration Micro-Field for Lamellar Eutectic Growth

2008 ◽  
Vol 272 ◽  
pp. 123-138 ◽  
Author(s):  
Waldemar Wołczyński
Keyword(s):  
Boundary Conditions ◽  
Mass Balance ◽  
Structure Formation ◽  
Concentration Field ◽  
Eutectic Growth ◽  
Solute Concentration ◽  
Liquid Interface ◽  
Eutectic System ◽  
Solid Liquid Interface ◽  
Solid Liquid

A possibility of a modification of the Jackson-Hunt theory of an oriented structure formation is analysed. A new model for the formation of a concentration field ahead of growing regular lamellae with respect to the solid / liquid interface shape is presented. A coordinate system applied in the model is attached to the solid / liquid interface to be advancing in the z - direction, identically with interface moving at a constant velocity, v . The solution to a diffusion equation is given for the improved formulation of the boundary conditions. The boundary conditions are related to the interplay between the diffusion required for phase separation and the formation of the interphase between both lamellae. The boundary conditions are formulated to establish the stability of lamellar structure formation under steady-state conditions. It is assumed that stable growth of the lamellae is ensured by the separation of concentration fields within a boundary layer ahead of the solid / liquid interfaces of both the α and β " phases. Coupled lamellar growth with the presence of a leading phase protrusion is defined. The general mass balance is analysed for a solute concentration in the liquid, taking into account a planar solid / liquid interface. A local mass balance is also ensured but it requires envisaging a protrusion of the minor eutectic phase. The existence of a lead distance is confirmed experimentally for the (Pb)-(Cd) eutectic system. The difference in undercooling is also considered as a phenomenon associated with the separation of concentration fields and the existence of a protrusion to relax the assumption of an isothermal interface (ideally coupled growth) given by the Hunt and Jackson theory.

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