Thermophysical Data for Numerical Simulation of Casting Processes

Binary-alloy module

In the binary-alloy module, interfacial material balance equations and Fick’s diffusion laws were combined with a thermodynamic solution model, which links the temperature, the interfacial composition and the phase stabilities to each other. The thermophysical properties of the solution phases are described with a substitutional solution model. Generally, the results depend not only on the alloy composition but also on the cooling rate. The module globally deals with non-equilibrium solidification, i.e., thermodynamic equilibrium is assumed to be achieved at the phase interfaces only. Binary-alloy module embraces thermophysical properties (Gibbs energy, enthalpy, entropy, specific heat capacity, thermal conductivity and density from the liquid state down to room temperature) for the following components: AlAg, AlCu, AlMg, AlSi, AlZn, CuAg, CuCr, CuFe, CuMg, CuMn, CuNi, CuSi, CuSn, CuTe, CuTi, CuZn, CuZr and FeSn. Depending on the alloy composition and cooling rate, the module also determines the phase fractions and compositions of the liquid during solidification.

In other words, the calculation algorithms are based on thermodynamic theory connected to thermodynamic assessment data, as well as on regression formulas of experimental data, and they take into account the temperature, the cooling rate and the alloy composition.

Main instruments

· Thermodynamic chemical-potential-equality equations

· Determination of thermodynamic equilibrium at the phase interfaces

· Based on substitutional solution and magnetic ordering models

· Interface mass balance equations

· Fick’s law of solute diffusion

· Complete solute mixing in liquid
· Diffusion of solutes extremely rapid during solidification

Input data

· Solute selection and composition

· Nominal composition [wt%] of a selected solute

· Minimum value: 1.0 wt% of solutes

· Maximum values given in "composition ranges" section

· Cooling rate

· Cooling rate [°C/s] of solidification

· Recommended values from 0.001 to 99°C/s]

· The cooling rate causes different temperature range and location of the mushy zone in the described material properties

· Data of the Thermo-Prop data bank

· Program’s module contains thermodynamic data and solute diffusion data

· Automatic input, not for user

Composition ranges

User should apply the recommended composition ranges given below. Going beyond these ranges does not prevent the calculations but the program restricts itself to these composition ranges.

· Composition ranges [wt%] for aluminium alloys

· Ag up to 30

· Cu up to 20

· Mg up to 20

· Si up to 12

· Zn up to 5

· Composition ranges [wt%] for copper alloys

· Ag up to 5

· Cr up to 1.4

· Fe up to 5

· Mg up to 9

· Mn up to 10

· Ni up to 15

· Si up to 7

· Sn up to 25

· Te up to 7

· Ti up to 16

· Zn up to 30

· Zr up to 10

· Composition ranges [wt%] for ferrous alloys

· Sn up to 20

Output data

· Thermophysical data

· Gibbs energy

· Enthalpy

· Entropy

· Specific heat capacity

· Thermal conductivity

· Density

· Miscellaneous data

· Solid fraction

· Nominal liquid composition of solute [wt%]

· Liquidus temperature (start of solidification)

After the execution of program, the results are displayed as xxxx % Solut. =…, Cool.r. =…, where xxxx refers to alloy designation; % Solut. refers to nominal liquid composition of solute [wt%]; and cool.r. refers to the cooling rate of solidification process.