abnormally high (and low) values of V concentration around a precipitate

[pmecozzi]

I have run simulations to study the precipitation of a VC particle in a supersaturated ferrite matrix. The simulation ran without problems when I set the nucleation in the bulk of the ferrite grain. When the diffusivity of vanadium in ferrite is set two orders of magnitude bigger than the values of the mobility database, the VC particle concentration approaches the stoichiometric values (see the attached Figure 1).
The problems arose when I set the nucleation of the VC particle at the grain boundary of two ferrite grains, whether I set the “interface” or “region” seed position the latter coinciding with the grain boundary. Vanadium concentration in ferrite around the particle reaches abnormally high positive and negative values (see the attached Figure 2) I suppose the problem is connected to the presence of the triple points. Could you please help me to solve this problem? Please find enclosed the driving files.
Kind Regards,

Pina Mecozzi

[Bernd]

Hi Pina,

Looking into you input files I notice that you are using several unusual settings in combination. Maybe, this leads to the problem.

My first guess would be that using "globalF" for interaction 2/4 together with infinite diffusion in phase 4 (VC) could cause the problem. Please note that "globalF" will create 2 different sets of linearisation parameters of your VC-grain to each of the BCC grains, if the latter is placed on the interface. Please try whether either using "globalG" or not using any diffusion in phase 4 will solve the issue. My second try would be to switch off interface diffusion at the 2/2 interface.

You are using MICRESS V7.0. It could also be that what you see comes from a software bug which we already fixed in later versions. I cannot check that without having the .GES5-file - please send it to me in case the above suggestion did not work.

Best wishes
Bernd

[pmecozzi]

Hi Bernd,

Thank you for the replay. I will make the corrections you suggested. If they do not solve the problem, I will send you the GES file.
I am still using the old version of MICRESS. I think it is time to change and move to Version 7.2.

Kind Regards,

Pina

[pmecozzi]

Hi Bernd,

I have solved the problem by replacing GlobalF with GlobalG.

Thank you for the help.

Kind Regards,

Pina