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Acta Metall Sin  2026, Vol. 62 Issue (3): 509-522    DOI: 10.11900/0412.1961.2024.00406
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Numerical Simulation of the Dynamic Contraction of Dendrite Solidification in the Al-4.7%Cu Alloy
ZHU Baofeng, LI Chenyu, ZHANG Shijie, LI Ri()
College of Materials Science and Engineering, Hebei University of Technology, Tianjin 300401, China
Cite this article: 

ZHU Baofeng, LI Chenyu, ZHANG Shijie, LI Ri. Numerical Simulation of the Dynamic Contraction of Dendrite Solidification in the Al-4.7%Cu Alloy. Acta Metall Sin, 2026, 62(3): 509-522.

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Abstract  

The dynamic formation process of microshrinkage pole in alloy castings is directly related to the dendrite solidification process. To simulate dendrite shrinkage in the Al-4.7%Cu (mass fraction) alloy during solidification, we proposed a coupling model combining cellular automata (CA) and the lattice Boltzmann method (LBM), referred to as the CA-LBM model. In this model, CA was used to simulate the formation of shrinkage pores during dendrite growth, whereas LBM was applied to study the diffusion process of shrinkage pores in the liquid phase (fully liquid conditions). First, the accuracy of the proposed CA-LBM numerical model was verified through the numerical simulation of the diffusion homogenization of a vacuum cavity in liquid. Then, the solidification process of a single dendrite—with and without dendrite shrinkage were compared, followed by the calculations of the multi-dendrite solidification contraction process with and without dendrite shrinkage. Simulations of the single-dendrite solidification process indicated that no internal pores were formed in the single dendrites when shrinkage was not considered. However, when shrinkage was considered, uniform microshrinkage pores appeared in the single dendrites. Moreover, the presence of shrinkage pores notably influenced dendrite morphology by promoting secondary branching. The results of the multidendrite contraction simulation also showed that micro-shrinkage pores tended to form at the junctions of the last solidified dendrites. A comparison between the calculated number of shrinkage poles and the theoretical value showed a small error, indicating the effectiveness and reliability of the proposed numerical model.

Key words:  Al-Cu alloy      solidification      dendrite shrinkage      CA-LBM numerical model     
Received:  28 November 2024     
ZTFLH:  TG111.4  
Fund: National Natural Science Foundation of China(51975182)
Corresponding Authors:  LI Ri, professor, Tel: (022)60202006, E-mail: hbcllr@hebut.edu.cn

URL: 

https://www.ams.org.cn/EN/10.11900/0412.1961.2024.00406     OR     https://www.ams.org.cn/EN/Y2026/V62/I3/509

Fig.1  A model of the microscopic shrinkage algorithm
ParameterVariableUnitValue
Solidus temperatureTmK917
Liquidus temperatureTlK821.7
Density of liquid phaseρlkg·m-32606
Solid densityρskg·m-32743
Solute diffusion coefficientDLm-2·s-13.0 × 10-9
Latent heat of crystallizationLJ·kg-1397000
Liquidus slopemlm·K·%-1-3.44
Liquid specific heat capacitycpJ·kg-1·K-11100
Thermal diffusion coefficientαm-2·s-12.7 × 10-7
Equilibrium distribution coefficientk-0.145
Liquid viscosityνm-2·s-11.2 × 10-6
Anisotropy coefficientε-0.0467
Gibbs-Thomson coefficientΓm·K2.4 × 10-7
Table 1  Thermophysical parameters of Al-4.7%Cu
Fig.2  Model flow chart (CA—cellular automata, LBM—lattice Boltzmann method)
Fig.3  Standard bounce format
Fig.4  Diffusion modeling of vacuum holes under nine grids
Fig.5  Nine-grid validations of initial conditions (a), diffusion process (b, c), and final results of the simulation (d) in vacuum cavity diffusion process (femp—shrinkage of a cell)
Fig.6  Twenty-five grid (a1-a4) and one-hundred grid (b1-b4) verifications in vacuum cavity diffusion process
(a1, b1) initial conditions (a2, a3, b2, b3) diffusion process (a4, b4) final results of the simulation
Fig.7  Computational domain of multigrid flow field in vacuum cavity diffusion process
(a) pure liquid phase (b) lateral obstacle (c) vertical-like obstacle
Fig.8  Condensation diffusion (first 3000 steps) in pure liquid phase (The depth of color only represents the concentration of shrinkage holes, the same below)
(a) 230 steps (b-o) continue to output the result of the calculation every 60 steps
Fig.9  Condensation diffusion in pure liquid phase (after 3000 steps)
(a) 3000 steps (b-o) continue to output the result of the calculation every 3000 steps
Fig.10  Schematics of shrinkage diffusion in a multigrid flow field with lateral obstacle (a1-a5) and vertical-like obstacle (b1-b5)
(a1) step = 120 (a2) step = 260 (a3) step = 430 (a4) step = 640 (a5) step = 770
(b1) step = 130 (b2) step = 240 (b3) step = 390 (b4) step = 560 (b5) step = 720
Fig.11  Schematics of two-point spread
(a) step = 90 (b) step = 130 (c) step = 180 (d) step = 240
Fig.12  Simulation results of monodendritic growth without considering shrinkage (a1-a5) and considering shrinkage generation and diffusion (b1-b5) (fs—solid fraction)
(a1, b1) step = 110 (a2, b2) step = 150 (a3, b3) step = 500 (a4, b4) step = 1321 (a5, b5) step = 1374
Fig.13  Comparisons of the total number of shrinkage holes obtained in single dendrite calculations with theoretical values (T¯average temperature of the universal grid, N—number of grids occupied by the total shrinkage hole volume)
Fig.14  Simulation results of polydendritic grains
(a) locations of 25 nucleation points
(b) polycrystalline grains with different site orientations
Fig.15  Schematics of polydendrite growth
(a) step = 160 (b) step = 340 (c) step = 1010 (d) step = 1328
Fig.16  Comparisons of the total shrinkage porosity obtained from the multi-dendrite calculations with the theoretical values
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