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phase transformation

Posted: Fri May 06, 2022 5:34 pm
by Jane
Dear Bernd,

I'm sorry to bother you again. I want to ask you a question about phase transformation. I found that cementite basically did not grow up when I was undergoing austenite-cementite binary transformation. The only thing that exists is me The added nucleation radius, the following is the driver file, can you help me find where the problem is? I'm sure this will be an easy problem for you, but I can't solve it.
Looking forward to your reply。
Best wishs.
Jane

Re: phase transformation

Posted: Fri May 06, 2022 9:08 pm
by Bernd
Dear Jane,

It seems that you lowered the temperature of transformation substantially, which automatically leads to much slower diffusion (see .TabD tabular output), and such to much slower phase transformations. I guess that this is the main reason for the low transformation rate.

Bernd

Re: phase transformation

Posted: Sat May 07, 2022 6:21 am
by Jane
Dear Bernd,

I think what you said makes sense, but the same thing happens when I raise the temperature, and the driving force dG is positive, I lowered the simulated temperature in order to bring the driving force dG down to a negative value. And another question here is that if I change the cementite_D011 to BCC, the reaction works normally, I don't understand why?

Jane

Re: phase transformation

Posted: Mon May 09, 2022 2:45 pm
by Bernd
Dear Jane,

You can understand all that in terms of diffusivity, because the diffusion coefficient of C is considerably higher in BCC than in FCC, while in cementite there is none.

If you adapt a simulation setup, which has been made for higher temperatures, to considerably lower temperatures (by ~500 K in your case), you have to take into account that due to slower diffusion you must change the length - and/or time scale of the simulation accordingly.

Bernd