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1
Content available 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
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2018
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Vol. 18, iss. 2
51--56
EN
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.
2
Content available Modeling of Dendritic Structure Evolution During Solidification of Al-Cu Alloy
Zyska A., Boroń K., Kordas P.
Archives of Foundry Engineering
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2018
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Vol. 18, iss. 4
87--92
EN
The paper presents the cellular automaton (CA) model for tracking the development of dendritic structure in non-equilibrium solidification conditions of binary alloy. Thermal, diffusion and surface phenomena have been included in the mathematical description of solidification. The methodology for calculating growth velocity of the liquid-solid interface based on solute balance, considering the distribution of the alloy component in the neighborhood of moving interface has been proposed. The influence of solidification front curvature on the equilibrium temperature was determined by applying the Gibbs Thomson approach. Solute and heat transfer equations were solved using the finite difference method assuming periodic boundary conditions and Newton cooling boundary condition at the edges of the system. The solutal field in the calculation domain was obtained separately for solid and liquid phase. Numerical simulations were carried out for the Al-4 wt.% Cu alloy at two cooling rates 15 K/s and 50 K/s. Microstructure images generated on the basis of calculations were compared with actual structures of castings. It was found that the results of the calculations are agreement in qualitative terms with the results of experimental research. The developed model can reproduce many morphological features of the dendritic structure and in particular: generating dendritic front and primary arms, creating, extension and coarsening of secondary branches, interface inhibition, branch fusion, considering the coupled motion and growth interaction of crystals.
3
Content available Simulation of Casting Technologies for Al-Si-Cu Plate Casting
Cupido L. H., Żak P. L.
Archives of Foundry Engineering
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2013
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Vol. 13, iss. 3 spec.
11--14
EN
During the casting of aluminium alloys, the susceptibility to form oxide films is high, due to the turbulent flow of the melt and constant exposure of new surface area. This have impact on the properties of the material and the service life of the casting components. Also, hydrogen solubility in the solid state are very low, which ends up being rejected and causing porosity. After pouring, when solidification occurs, another phenomenon arise called shrinkage. This require excess molten metal to be fed during this phase change to eliminate or reduce the effect of volumetric changes. Filling and feeding during aluminium casting is therefore of paramount importance, and careful steps needs to be undertaken to reduce possible defects in the castings. The objective is to apply studied literature guides and rules and simulate the casting process of aluminium alloys, and understand the how certain defects are occurring during this process. This is a preliminary study towards the understanding of the “macro evolution” of Al-Si-Cu alloy during solidification, which will be the bases for the study of microsegregation of the specified alloy.
4
Content available Problem of the moving boundary in continuous casting solved by the analytic-numerical method
Grzymkowski R., Pleszczyński M., Hetmaniok E.
Archives of Foundry Engineering
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2013
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Vol. 13, iss. 1
33--38
EN
Mathematical modeling of thermal processes combined with the reversible phase transitions of type: solid phase – liquid phase leads to formulation of the parabolic or elliptic moving boundary problem. Solution of such defined problem requires, most often, to use some sophisticated numerical techniques and far advanced mathematical tools. The paper presents an analytic-numerical method, especially attractive from the engineer’s point of view, applied for finding the approximate solutions of the selected class of problems which can be reduced to the one-phase solidification problem of a plate with the unknown a priori, varying in time boundary of the region in which the solution is sought. Proposed method is based on the known formalism of initial expansion of a sought function, describing the field of temperature, into the power series, some coefficients of which are determined with the aid of boundary conditions, and on the approximation of a function defining the freezing front location with the broken line, parameters of which are determined numerically. The method represents a combination of the analytical and numerical techniques and seems to be an effective and relatively easy in using tool for solving problems of considered kind.
5
Content available Numerical analysis of influence of the mold material on the distribution of shrinkage cavities
Dyja R.
Archives of Foundry Engineering
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2013
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Vol. 13, iss. 1
15--18
EN
Production of castings, like any other field of technology is aimed at providing high-quality product, free from defects. One of the main causes of defects in castings is the phenomenon of shrinkage of the casting. This phenomenon causes the formation of shrinkage cavities and porosity in the casting. The major preventive measure is supplementing a shortage of liquid metal. For supplement to be effective, it is necessary to use risers in proper shapes. Usually, the risers are selected on the basis of determination the place of formation of hot-spots in the castings. Although in these places the shrinkage defects are most likely to occur, shape and size of these defects are also affected by other factors. The article describes the original program setting out the shape and location of possible cavities in the casting. In the program is also taken into account the effect of temperature on the change in volume of liquid metal and the resultant differences in the shape and size of formed shrinkage cavities. The aim of the article is to describe the influence that have material properties of the mold on the simulation results.
6
Content available Effect of Mesh Quality on the Numerical Solution of the Solidification of Pure Metal
Skrzypczak T., Węgrzyn-Skrzypczak E.
Archives of Foundry Engineering
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2013
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Vol. 13, iss. 2 spec.
89--92
EN
The paper presents a method of mathematical and numerical modelling of directional solidification process of pure metal in the two-dimensional region. In this case, the thermal conditions associated with the process favours the occurrence of sharp solidification front. The mathematical description of the process is based on the Stefan formulation with appropriate continuity conditions on the solid-liquid interface. The numerical model is based on the finite element method (FEM). The calculations were made on a fixed mesh with diffused solidification front to avoid the difficulties associated with the discontinuity. Temporary position of the interface was calculated with the use of the level set method (LSM). Effect of the quality of the spatial discretization on the accuracy of numerical solution was investigated. Obtained results of the temporary front position were compared with the analytical solution. The correlation between the quality of the spatial discretization and the accuracy of the results was observed. Methods used in the work had significant impact on the computation time and helped avoid the explicit consideration of discontinuity of heat flux on the front.
7
Content available Calculation of phase-change boundary position in continuous casting
Ivanova A. A.
Archives of Foundry Engineering
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2013
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Vol. 13, iss. 4
57--62
EN
The problem of determination of the phase-change boundary position at the mathematical modeling of continuous ingot temperature field is considered. The description of the heat transfer process takes into account the dependence of the thermal physical characteristics on the temperature, so that the mathematical model is based on the nonlinear partial differential equations. The boundary position between liquid and solid phase is given by the temperatures equality condition and the Stefan condition for the two-dimensional case. The new method of calculation of the phase-change boundary position is proposed. This method based on the finite-differences with using explicit schemes and on the iteration method of solving of non-linear system equations. The proposed method of calculation is many times faster than the real time. So that it amenable to be used for model predictive control of continuous semifinished product solidification.
8
Content available remote 3D simulation of alloy solidification in the NuscaS system
Dyja R., Mikoda J.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
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2011
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Vol. 10, nr 1
33-40
EN
The authors present the capabilities of the authorial software in the field of engineering simulation. This system uses the finite element method. It enables the performance of simulations of phenomena described by partial differential equations. Currently the NuscaS system consists of: a library of finite elements, a finite elements mesh generator as well as modules for performing simulations of heat transfer and solidification. The module of solidification enables one to conduct simulations of equilibrium solidification of two component alloys for three-dimensional problems. This paper presents the results of exemplar simulations that illustrate the capabilities of the described tool. These results consist of cooling curves, charts of part of the solid phase in the cast, fields of temperature in the cast and casting mould. The paper concludes with remarks and discussion of the obtained results.
9
Modelowanie ewolucji mikrostruktury stopu dwuskładnikowego techniką automatu komórkowego
Marek M.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
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2005
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z. 80
95-102
PL
W artykule przedstawiono opis modelu krzepnięcia dendrytycznego stopu dwuskładnikowego wykorzystującego technikę automatu komórkowego oraz przykładowe mikrostruktury uzyskane dla modelowego stopu przy krzepnięciu objętościowym i kierunkowym.
EN
Cellular automaton model of dendritic solidification of binary alloy is described in the paper. Some results of equiaxed and directional solidification modelling are also shown.
10
Content available remote Modelowe badania przemiany perytektycznej
Fraś E., Kapturkiewicz W., Burbelko A., Lopez H.
Krzepnięcie Metali i Stopów
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1998
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nr 36
9--17
PL
Przemiana perytektyczna jest jedną z kilku przemian fazowych zachodzących przy krzepnięciu stopów, która prowadzi do utworzenia struktury wielofazowej. Liczba publikacji z zakresu krystalizacji perytektycznej jest niewielka [1-10] i podstawowe pojęcia z tego zakresu są różnie interpretowane przez poszczególnych autorów. [...]
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