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Modification Mechanism and Growth Process of Al3(Sc, Zr) Particles in As-cast Al-Si-Mg-Cu-Zr-Sc Alloy

Li Y., Du X., Fu J., Zhang Y., Zhang Z., Zhou S., Wu Y.

Archives of Foundry Engineering

2018

Vol. 18, iss. 2

51--56

In this study, the modification mechanism and growth process of Al3(Sc, Zr) particles in as-cast Al-Si-Mg-Cu based alloy with addition of Sc and Zr were systematically investigated. It was found that 0.57 wt-%Sc addition caused a significant refinement in the average grain size of the investigated alloy, which brought about a remarkable transformation in as-cast microstructure, from thick dendritic shape to fine equiaxed structure. A large amount of primary Al3(Sc, Zr) particles with the dimension of around 5-6 μm were also observed within the equiaxed grain. Due to the identical orientation and similar crystal structure between primary Al3(Sc, Zr) particles and α-Al matrix, the primary particles always served as heterogeneous nucleus for the α-Al matrix. In addition, these cusped cubic primary Al3(Sc, Zr) particles showed triangle, star, rhomboid morphologies are generated from sectioning the particle in (111), (100) and (110) planes, respectively. Particularly, the typical eutectic structure which contained odd number-layer (Al3(Sc, Zr)+α-Al+ ... +Al3(Sc, Zr)) was observed within the investigated particles.

Cellular automata modeling of cooperative eutectic growth

Burbelko A., Gurgul D., Fraś E., Olejnik E.

Archives of Foundry Engineering

2010

Vol. 10, iss. 1 spec.

29--34

The model and results of the 2D simulation of the cooperative growth of two phases in the lamellar eutectic are presented. The proposed model takes into account heat transfer, components diffusion and nonstationary concentration distribution in the liquid and solid phases, non-equlibrium nature of the phase transformation and kinetics of the growth, influence of the surface energy and interface curvature on the conditions of the thermodynamic equilibrium. For the determination of the phase interface shape the Cellular Automata technique (CA) was used. For the calculation of temperature and concentration distribution the numerical solution of the Fourier equation was used. The partial differential equations were solved by Finite Differences Method (FDM). The spatial position and cell sizes of CA lattice and FDM mesh are equal. Proposed model can predict the steady state growth with a constant interlamellar spacing in the regular plate eutectic, as well as some transient processes that bring to the changes of that parameters. Obtained simulation data show the solid-liquid interface changes result in the termination of lamella and enlargement of interlamellar spacing. Another simulation results illustrate a pocket formation in the center of one phase that forestalls nucleation (or intergrowth) of the new lamellae of another phase. The data of the solidification study of the transparent material (CBr4– 8,4% C2Cl6) obtained in the thin layer demonstrate the qualitative agreement of the simulation.