Wyniki wyszukiwania - BazTech

1

Modeling of Dendritic Structure Evolution During Solidification of Al-Cu Alloy

Zyska A., Boroń K., Kordas P.

Archives of Foundry Engineering

|

2018

|

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.

2

3D simulation of alloy solidification in the NuscaS system

Dyja R., Mikoda J.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

|

2011

|

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.

3

Eulerian equilibrium and non-equlibrium macroscopic modelling of binary system solidification

Banaszek J., Furmański P., Browne D.

Archives of Thermodynamics

|

2003

|

Vol. 24, no 1

37-57

EN

Two models of macroscopic computer simulation of binary system solidification on a fixed grid are discussed. First, it is shown that the single-domain enthalpy-porous medium model not only provides complete information on the evoluation of macroscopic entities, but also enables a detailed analysis of the role of the mushy zone properties in the progress of solidification. In this context, the results of FEM calculations for aqueous ammonium chloride solutions are presented showing the importance of anisotropy of permeability and thermal conductivityof the mushy zone. Next, to account for non-equilibrium phenomenon of the constitutional undercooling a new front tracking technique on a fixed grid, which is based on the kinetics of dendritic growth, (see a companion paper [13]), is used. The model is compared with the enthalpy approach showing its superiority in the detection of the undercooled zone in front of dendrite tips and, thus, in modelling of columnar /equiaxed grain structures. It is, then, further used to address the question of the influence of alloy composition on the size of the undercooled liquid zone in front of columnar dendrite tips during solidification of Al-Cu alloys driven by conduction in a square mould. Eventually, a possible scenario of the coupling of both models, in order to develop a comprehensive computer simulation of binary alloys solidification driven by both conduction and natural convection, is outlined.

4

An interface-tracking model of moving boundaries in multi-phase systems: application to solidification

Browne D., Hunt J.

Archives of Thermodynamics

|

2003

|

Vol. 24, no 1

25-36

EN

A new approach to modelling of phase boundary migration is presented. In particular, a meso-scale model of alloy solidification, which can resolve solid grain boundaries as they grow through the diminishing liquid phase, has been developed. The initial condition is of a superheated, but cooling, liquid alloy in a domain with a mixed thermal boundary condition. After activation via nucleation of solid, the model tracks the phase boundaries as discrete fronts across a fixed computational grid, and the kineticsof motion are derived from theories of dendritic growth. Each interface is formed by interpolation between representative computational markers, and is the boundary between liquid and partial solid with a dendritic morphology. The model simulates the non-equilibrium growth of both a columnar front and equiaxed grains, and can thus be used to predict the final grain structure in metallic alloy castings. The evolution of microstructure and heat are fully coupled in the formulation. The method is illustrated by the example of the simulation of Al-Cu alloy solidification.