An Example KDB File for a Mg-based AZ91 Alloy Considering Shape Factor and Shape Evolution

Reference Folder: $Pandat_Installation_Folder\Pandat 2024 Examples\PanEvolution\AZ91_Morphology\AZ91.kdb

  • Consider shape factor but shape factor not evolve (AZ91_200C.pbfx)

<PrecipitatePhase name="ALMG_GAMMA" model="kwn"

morphology="Cylinder" nucleation="Modified_Homo" growth="sffk">

In this case, the morphology must be set to “morphology="Cylinder"” and the keyword “Aspect_Ratio” or “A_R” is used to set the aspect ratio of the particles: <Parameter type="A_R" value="0.15" description="aspect ratio" />

In this example, the Aspect Ratio is set as a constant during the particle evolution.

  • Shape evolution (AZ91_200C_shape_evolution.pbfx)

<PrecipitatePhase name="ALMG_GAMMA" model="KWN" morphology="Cylinder"

   nucleation="Modified_Homo" growth="SFFK_Shape_Evolution">

    In order to consider shape evolution, the morphology must be set to “morphology="Cylinder"” and the growth model should be set to “growth="SFFK_Shape_Evolution"”.

    In this case, the aspect ratio value set in “<Parameter type="A_R" value="1" description="Initial aspect ratio" />” will be used as a starting value and evolves during precipitation process.

    There are two sets of parameters that can control the shape evolution. The first set includes the interfacial energies of the two different directions:

<Parameter type="Interfacial_Energy" value="0.25" description= "Interfacial Energy" />

<Parameter type="Interfacial_Energy_L" value="0.05" description= "Interfacial Energy in L direction"/>

    The second set includes the anisotropic misfit strain of the precipitate and its model parameters can be defined as follows:

<Parameter type="Shear_Modulus" value="30e9" description="the shear modulus, in Pa"/>

<Parameter type="Volume_Misfit" value="0.02" description="the volume misfit"/>

    It should note that user can set parameters for either interfacial energy or strain energy or both to control the shape evolution.