MICRESS Forum

Dear Bernd,

I hope this message finds you well.
I am currently utilizing the nucleation function in MICRESS for my analysis, and I would like to gain a deeper understanding beyond what is provided in the official documentation.

For example, I am interested in the following aspects:
How is the initial solute concentration of a nucleus determined upon its formation?
How is the overall solute conservation maintained throughout the process?
Additionally, how is the distribution of phase-field variables adjusted when a nucleus forms?

If there are any papers or publications that explain these topics in detail, I would greatly appreciate it if you could share them.

Thank you very much for your time and assistance.

Best regards,
Chika

Dear Chika,

Before nucleation, the phase composition of the reference phase is evaluated exactly in the grid cell where nucleation is positioned to. Using the local temperature (and optionally interface curvature and local stress), the driving force for nucleation is calculated. In case of a new phase, the phase interaction between the nuclei phase and the reference phase has to be initialized before.

If the required nucleation undercooling is reached (ΔT=ΔG_nuc/ref/ΔS_nuc/ref), the nucleus is set in terms of phase-field parameter. In case of a "small grain" (i.e. if a nucleus radius of 0 is chosen), only a fraction of 2*phMin (phMin is the smallest phase fraction defined in the input file) of the nuclei phase is added without changing the total composition of the grid cell. The same fraction is subtracted from the reference phase to keep fraction balance. In case of a large grain, the cell is completely overwritten by 100% of the new phase, but again without changing the mixture composition to avoid violation of the total concentration balance. This may lead to serious problems with TQ-coupling and therefore is not recommended.

I will be happy to answer further questions or to clarify any doubts.

Bernd

Dear Bernd,

I am grateful for your kind response.
I could understand the logic of nucleation in MICRESS well.

Best regards,
Chika