An Example KDB file for Heterogeneous Nucleation

Reference Folder: $Pandat_Installation_Folder\Pandat 2022 Examples\PanPrecipitation\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. 2 with Taking Vm = 3.9e-5 and s = 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.

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