Recrystallisation

ripening phenomena, dislocations, grainboundary topology
Bernd
Posts: 1250
Joined: Mon Jun 23, 2008 9:29 pm

Re: Recrystallisation

Post by Bernd » Thu Mar 25, 2021 8:01 pm

Dear Kamran,

Unfortunately, I am not so much experienced in recrystallisation in general. Thus, I don't know what are typical values of critical reX-energy or dislocation density for nucleation, and also not for the energy threshold for recrystallisation model. Clear is that the latter should be much smaller than typical deformation energies, while the critical reX-energy for nucleation should be somewhere inside the range of deformation energies in order to be somehow selective. The only way of determining these input values is probably by calibration with experimental results...

For calculation of the driving force for phase transformations in MICRESS, the reX-energy difference is added to the chemical driving force. However, for nucleation, you currently can only chose either reX-energy or undercooling. However, as far as I understand, adding strain energy to the driving force for nucleation of austenite would favor nucleation on deformed grains rather than on recrystallized grains. Thus, your observations cannot be explained from an energetic view but must have another reason.

Of course, you can do recrystallisation simulations during isothermal holding. You can also start from a microstructure which has been simulated earlier by using "initial microstructure from restart file" (or "restart structure_only" in earlier MICRESS versions 6.xx).

When creating initial microstructures using the Voronoi construction, only the center positions and the ratio of the radii are important for the outcome. The absolute values of the radii or radii ranges do not enter.
I recommend using an interface thickness of 3-4 cells.

Bernd

Kamran
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Joined: Mon Apr 27, 2020 11:51 pm
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Re: Recrystallisation

Post by Kamran » Thu Mar 25, 2021 10:10 pm

Thank you Brend for your prompt reply
but, actually my simulated grains are in elliptical shape and there is not minimum and maximum grain radius, there should be curvature for elliptical martensite, but it is not accepted during simulation.
unfortunately I could not see straight explanation for elliptical grains like martensite morphology
so, I have only considered maximum and minimum length scales of X and Z directions

my another problem is some curved shapes instead of elliptical shapes
other problem reveals when you consider recrystallization for martensite, you can see for the same codes for nucleation of initial microstructure, we have different microstructures for with and without considering REX, even before happening,
maybe due to changing isotropic term to anisotropic one in Data for phase 1 :idea:
thank you for your patience and support

Bernd
Posts: 1250
Joined: Mon Jun 23, 2008 9:29 pm

Re: Recrystallisation

Post by Bernd » Fri Mar 26, 2021 12:32 pm

Dear Kamran,

Maybe I misunderstood you. If you want to have explicitly elliptical grains, and not just a distorted grain structure, then you should use "no_voronoi" when defining the initial microstructure.

Bernd

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