MICRESS Forum

Hej Bernd,

What is the purpose of nucleation noise . Does it has a significant impact on resultant microstructure.

BR
Chamara

Dear Chamara,

nucleation noise is mainly useful if you start from a homogeneous RVE, eg. melt which is cooled down without any T-gradient. In such a case, all seeds of the same type would come exactly at the same time which is not realistic.

Furthermore, noise can be an element for people who like stochastic nucleation models...

Bernd

Hej Bernd,

Thanks for the explanation.

Also, does the noise factor affect by cooling rates?

BR
Chamara

Dear Chamara,

no, the noise has no relation with cooling rates.

Bernd

Hej Bernd,

When you defining nucleation data for precipitation in a heat treatment simulation, the undercooling should be defined as 0, since there is only a constant temperature.

BR
Bernd

No, because for nucleation, the seed must overcome a critical seed radius which requires still an undercooling. Change of temperature is only one source for undercooling, while composition change is a second one.

Bernd

HEj Bernd,

I am ruining a solidification simulation with seed density model. There is no grains at the beginning.

When I change the noise factor and random number for nucleation noise, I don't get any change in the nucleation location. Seeds starts to appear at the same position irrespective of the noise parameter change. I would expect it to be change since noise bring stochastic to the model.

Is this normal?

BR
Chamara

Hi Chamara,

Yes, it is normal. At the place where you define nucleation noise (what, by the way, does not make that much sense with "seed_density"), the random seed integer value is just for the noise.

With the seed_density model, the seed positions are created already during initialisation, and will not change during run-time. The random seed for the seed positions you specified already when defining the seed-density distribution. You should make changes there if you want to get different sets of random seed positions.

Bernd

Many thanks as always

HI Bernd,

Usually there is less nucleation barrier at the grain boundaries compare to the inside of the grain. This is the reason for seeing precipitation of delta phase at grain boundary first. How can we simulate this effect in MICRESS. What options do I have?

BR
Chamara