solid-state phase transformation

[zelin zhang]

Dear Bernd,

I would like to ask for your help regarding a problem I encountered in MICRESS during pearlite transformation simulations.

In my simulations, the pearlite transformation behaves normally when stress coupling is not considered. The lamellar structure forms correctly and remains stable throughout the simulation.

However, after enabling stress coupling, I observe a different behavior:

In the early stage, the microstructure evolution is still reasonable, and the pearlite lamellae form as expected.
In the later stage, the cementite lamellae become unstable. They tend to break, merge, or become distorted, leading to abnormal pearlite morphology.

I have also tried to adjust the interface properties between ferrite and cementite. Specifically, I reduced the interface mobility and increased the interface energy between these two phases. However, these modifications did not resolve the issue, and the instability of cementite lamellae in the later stage still persists.

I would like to ask how this problem could be addressed, and whether there are recommended strategies to improve the stability of cementite lamellae under stress coupling.

Any advice or suggestions would be greatly appreciated.

Thank you very much for your help.

Best regards,
Zelin Zhang

[Bernd]

Dear Zelin Zhang,

This is difficult to say without having more details on the simulation and the type of instability. The molar volumes of the phases as well as the stress boundary conditions have the most strong impact on the mechanical coupling. However, other settings may also have an influence and trigger such a behaviour.

The next steps should be to find out how the instabilities play out exactly. Are they only connected to the elastic driving force (.dGsp-output)? Is this effect realistic with respect to its relative strength? Or is there also some impact of stress on the concentration distribution in the phases, which may indirectly lead to instabilities?

If you get stuck with this problem, you may send your input file (including all required input so that I can try to reproduce the described behaviour).

Bernd

[zelin zhang]

Dear Bernd,

I will send you the driving file via private message, and I would be very grateful if you could take a look and help me with this issue.

Thank you very much for your help.

Best regards,
Zelin Zhang

[Bernd]

Dear Zelin Zhang,

Thanks for sending your input file. But for running your input file I also need the .ges5-file (FeC_ALL.ges5)...

Bernd