MICRESS Forum

Dear Sudhindra,

I would consider two possible reasons:

1.) Resolution is not fine enough. This is easily possible because of the extremely small diffusion length at 400°C.

2.) You use a constant small value for the interface mobility which cannot fit for all temperatures. I would try to use mobility correction in order to automatically adjust to diffusion-limited growth:
- increase the mobility by some orders of magnitude (e.g. 1.E-10)
- replace "normal" in the phase diagram data for 1/2 interaction by "normal mob_corr" to adjust mobility automatically to values <1.E-10

Bernd

Dear Bernd,
Can you provide some theoretical background on this automatic mobility correction? How does it account for the change of mobility and what all factors does it consider (Just to get a better idea of how this feature works). Thanks.

Deepu.

Dear Deepu,

there is a publication on that which besides the antitrapping current (atc) also explains the mobility correction (mob_corr):

A.Carré, B.Böttger, M.Apel
Implementation of an antitrapping current for a multicomponent multiphase-field ansatz
Journal of Crystal Growth 380(2013)5–13

Bernd

Dear Bernd,

I am conducting phase field simulation of phase transition from BCC_B2 to FCC_L12 in FE_CU_NI ternary alloy through MCRESS. My idea is to make CU gather to the center and make NI diffuse to the outside of CU to form a core-shell structure. The specific schematic diagram is as follows, but such situation does not occur in my simulation. Therefore, I hope you can provide some reference for me, or do you have any good methods?
Looking forward to your reply.

Best wishes
lv

Dear lv,

What goes wrong? Is it the Cu-composition which you display in the MICRESS-results below? May it be that you get FCC_L12#2 instead?

Bernd

Dear Bernd,

I am sorry that I did not explain the simulation results in MICRESS. The following diagram shows the concentration distribution of corresponding elements in phase FCC_L12, but it is not the core-shell shape I mentioned in the diagram. The Ni element does not diffuse around Cu and surround It. Why do you think that is? These are my related questions. Thank you very much.

Best wishes
lv

Dear lv,

For understanding why a core-shell structure should form, it is necessary to know composition and temperature, and to have a look onto the isothermal (triangular) section of the ternary phase diagram at this temperature. What you show above is probably the binary Fe-Cu-system.

A core-shell-structure typically is a non-equilibrium system. If the Ni-rich shell would be formed by diffusion as you suggested before, you would need uphill-diffusion which seems unlikely.

On the other hand, if the Ni-rich shell formed by redistribution, it would consist of bcc-phase (and thus you cannot see it in the MICRESS outputs of the fcc-composition which you present).

Bernd

Dear Bernd,

I have drawn the phase diagram of Fe-Cu-Ni ternary alloy through ternary phase diagram, and what is shown here is indeed a ternary system. As you said, diffusion is impossible, so I want to form Ni shell through redistribution. If it is convenient for you, I can send you my driver file.

Best wishes,
lv