The Solidification Kinetic Database Syntax and Examples

The Solidification kinetic database (.SDB) uses the XML format, which defines the back diffusion model for the morphology of primary phase and its corresponding model parameters such as interfacial energy, latent heat, coarsening geometric factor, dendrite tip factor, solute trapping parameter, solid diffusivity factor, boundary layer factor, and so on.

In the SDB, a series of alloys can be defined. A sample SDB file is given below,

<Alloy name="Mg alloys">

<solvent name="Mg"/>

<primary_phase name="Hcp"/>

<ParameterTable name="">

<Parameter name="coordinate" value="0" description = "geometry of dendrite. 0 for plate; 1 for cylinder; 2 for sphere" />

<Parameter name="interfacial_energy" value="0.065" description = "interfacial energy, unit = J/m^2"/>

<Parameter name="latent_heat" value="5.5e8" description = "latent heat, unit=J/m^3"/>

<Parameter name="solute_trapping_parameter" value="1e-9" description = "solute trapping parameter, unit=m"/>

<Parameter name="sound_velocity" value="1000" description = "sound velocity, unit=m/s"/>

<Parameter name="coarsening_geometric_factor" value="40" description = "No unit"/>

<Parameter name="dendrite_tip_factor" value="1" description = "No unit"/>

<Parameter name="solid_diffusivity_factor" value="0.2" description = "No unit"/>

<Parameter name="boundary_layer_factor" value="1" description = "No unit"/>

</ParameterTable>

</Alloy>

</sdb>

In this sample SDB, “Mg alloys” is defined as the name of the alloy, the primary phase is thus set as “Hcp” phase. A set of parameters for each phase, such as interfacial energy, latent heat and so on, can be defined in “ParameterTable”.

The solute trapping parameters can also be defined through the SDB file. First enable the solute trapping model by setting “non_equilibrium_interface” to 1. The solute trapping effect for a given velocity can be increased or decreased by adjusting the “solute_trapping_parameter” value, where a higher value enhances solute trapping and a lower value reduces it. If the desired solute trapping is still not achieved, the “solute_drag_parameter” can be used to further enhance the effect. Additionally, if the user wishes to skip the diffusion calculation during the solute trapping simulation, they can include the "skip_diffusion" tag in the SDB file. Below is a typical SDB file parameters for solute trapping of Al alloys.

<Alloy name="Al_alloy_noneq" >

<solvent name="Al" />

<primary_phase name="Fcc" />

<skip_diffusion value="True" description="True or False :" />

<ParameterTable name="" >

<Parameter name="coordinate" value="0" description="geometry of dendrite. 0 for plate; 1 for cylinder; 2 for sphere" />

<Parameter name="interfacial_energy" value="0.167" description="interfacial energy, unit=J/m^2" />

<Parameter name="latent_heat" value="1.36e9" description="latent heat, unit=J/m^3" />

<Parameter name="solute_trapping_parameter" value="1.0e-9" description="solute trapping parameter, unit=m, typical range: (0.2nm-2nm)" />

<Parameter name="sound_velocity" value="1000" description="sound velocity, unit=m/s" />

<Parameter name="coarsening_geometric_factor" value="35" description="No unit" />

<Parameter name="dendrite_tip_factor" value="1" description="No unit" />

<Parameter name="solid_diffusivity_factor" value="1" description="No unit" />

<Parameter name="boundary_layer_factor" value="1" description="No unit" />

<Parameter name="non_equilibrium_interface" value="1" description="Non equilibrium model, default=0. Options: 0 for equilibrium, 1 for Ludwig nonequilibrium" />

<Parameter name="solute_drag_parameter" value="0.0" description="Applies only to Non-equilibrium model, default=0.0, Range:(0.0-1.0)" />

</ParameterTable>

</Alloy>

The kinetic model parameters that can be defined under “ParameterTable” are listed in Table 1.

Table 1:  Kinetic model parameters in sdb
Name Unit Description

Coordinate

 N/A

Describe the geometry of dendrite for back diffusion model
<Parameter name="coordinate" value="0" description = "geometry of dendrite. 0 for plate; 1 for cylinder; 2 for sphere" />

Interfacial_Energy

 J/m2

Interfacial energy
<Parameter name="interfacial_energy" value="0.065" description = "interfacial energy, unit = J/m^2"/>

Latent_heat

 J/m3

Latent Heat of the alloy with unit of J/m3

<Parametername="latent_heat" value="5.5e8" description = "latent heat, unit=J/m^3"/>

Solute_Trapping_Parameter

 m

Used to define diffusion velocity () for solute: where is the diffusivity of solute and is the “solute trapping” parameter, typical range is 0.2nm – 2nm.
<Parameter name="solute_trapping_parameter" value="1e-9" description = "solute trapping parameter, unit=m"/>

Sound_velocity

 m/s

Maximum possible crystal growth velocity. Can be approximated by speed of sound in the alloy. Typical range 500 m/s – 2000 m/s

<Parameter name="sound_velocity" value="1000" description = "sound velocity, unit=m/s"/>

Coarsening_Geometric_Factor

 N/A

A factor adjusting adjust the coarsen speed of the dendrite
<Parameter name="coarsening_geometric_factor" value="40" description = "No unit/>

Non_Equilibrium_Interface

 N/A

A parameter define the solute trapping model
<Parameter name="non_equilibrium_interface" value="1" description = "Non equilibrium model, default=0. Options: 0 for equilibrium, 1 for Ludwig nonequilibrium model"/>

Solute_drag_parameter

 N/A

This parameter represents the free energy dissipation due to solute-redistribution: ; where is the solute drag parameter.
<Parameter name="solute_drag_parameter" value="0" description = "Applies only to Non-equilibrium model, default=0.0, Range:(0.0-1.0)"/>