An Example KDB file for Heterogeneous Nucleation

Reference Folder: $Pandat_Installation_Folder\Pandat Examples\PanEvolution\AA6005_yield_strength\AA6xxx.kdb

There are two parameters need to be adjusted in order to consider heterogeneous nucleation. In this example, the heterogeneous nucleation sites and barrier energy are adjusted manually by user:

  1. Nucleation_Site_Parameter; in the above example of AA6005 alloy, the value of 0.3e-5 was chosen based on experimental data.
  2. Re-define the nucleation barrier energy. In this example, the nucleation barrier energy for the heterogeneous nucleation is manually adjusted. For homogeneous nucleation, the nucleation barrier energy is defined by Eq. 5.2 with Taking Vm = 3.9e-5 and σ = 0.4 in the kdb file as shown in Section An Example KDB File for AA6005 Al Alloy, we get the nucleation barrier energy for the homogeneous nucleation as 1.63e-9/ dgm(*)^2. For heterogeneous, the nucleation barrier energy is ~2-3 order smaller than that of homogeneous nucleation. In this example, a value “7.475e-12/dgm(*)^2” is used. This value is optimized by using experimental data.

<VariableTable name="Variables replacing built-in variables">

<Parameter type="Nucleation_Barrier_Energy" value="7.475e-12/dgm(*)^2" description="Nucleation_Barrier_Energy"/>

</VariableTable >

where dgm(*) is the calculated thermodynamic driving force, which will be update at every simulation steps.