Simulation of solidification of Gamma prime alloy during SLM process

dendritic solidification, eutectics, peritectics,....
CharMIC
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Simulation of solidification of Gamma prime alloy during SLM process

Post by CharMIC » Wed Jun 05, 2019 7:06 am

Hi Bernd,

I think its good to create a new topic for this since it might be valuable in future. :)

CharMIC
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Re: Simulation of solidification of Gamma prime alloy during SLM process

Post by CharMIC » Wed Jun 05, 2019 7:11 am

Regarding getting larger undercooling (around 18K) for nucleation of FCC_L12#3....

Nucleation for FCC_L12#3 was set at the S/L interface. so using analytical_curvature was giving error, and therefore I had to use stabilization model. but I tried analitical_curvature model changing the FCC_L12#3 nucleation site to bulk (in Liquid). There also I started to get errors.

Bernd
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Re: Simulation of solidification of Gamma prime alloy during SLM process

Post by Bernd » Wed Jun 05, 2019 2:43 pm

Hi Chamara,

For me this seems to be an indication that the errors occur once FCC_L12#3 is really growing - probably these errors need to be analyzed first. Which kind of error messages do you get? Do you have all elements in this phase set to stoichiometric (FCC_L12#3 is carbide, isn't it?)?

Bernd

Bernd
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Re: Simulation of solidification of Gamma prime alloy during SLM process

Post by Bernd » Wed Jun 12, 2019 12:21 pm

Hi Chamara,

Thanks for sending me your updated MICRESS input file. Now, nucleation of MC phase (FCC_L12#3) produces just 1 error per nucleation event, directly after nucleation. This is not astonishing given the fact that you have given them an initial radius of 0.002 µm which corresponds to an already considerable initial fraction. Thus, in the first time step after nucleation, there is not enough carbon in the corresponding grid cell which is needed to form such an amount of MC with close to 50 at% C! However, MICRESS recovers immediately, and the grains become big without further problems. So you need not worry about it. Reducing the initial radius would certainly remove the error message.
The crash you show is due to a stupid bug which somehow found its way into the 6.404 version. It randomly occurs only if the first equilibrium for calculation of diffusion coefficient failed, and a second trial is needed. You had this error 22 already before...
I guess, Ralph will send you a fixed executable soon.

Bernd

CharMIC
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Re: Simulation of solidification of Gamma prime alloy during SLM process

Post by CharMIC » Wed Jun 12, 2019 2:50 pm

many thanks Bernd.

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Re: Simulation of solidification of Gamma prime alloy during SLM process

Post by CharMIC » Mon Jun 17, 2019 2:07 pm

Hi Bernd,

Solved the problem with errors during the nucleation of MC. However, I get this error message during the nucleation of gamma' phase
Error_1.PNG
Error_1.PNG (26.29 KiB) Viewed 369 times
is this related to calculating the equilibrium.

I have used "diff_comp_sets 1 2 3.

1 - gamma
2 - MC
3 gamma'

Bernd
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Re: Simulation of solidification of Gamma prime alloy during SLM process

Post by Bernd » Mon Jun 17, 2019 5:43 pm

Hi Chamara,

The error is related to calculating diffusion coefficients for the fcc phase. Thus, it is not related to the γ'-phase!
The error occurs when calculating equilibrium using the average fcc composition. According to your "diff_comp_sets" definition, MC and γ' are included in this equilibrium.

If the error does'nt occur excessively, you probably can ignore it. If you have doubts, you can check the .diff output and compare the calculated coefficients to those obtained earlier.

Bernd

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Re: Simulation of solidification of Gamma prime alloy during SLM process

Post by CharMIC » Thu Jun 20, 2019 1:54 pm

Hi Bernd,

is it okay to define a larger radius for the grain size than the grid spacing in analytical_curvature model?

Bernd
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Re: Simulation of solidification of Gamma prime alloy during SLM process

Post by Bernd » Thu Jun 20, 2019 2:17 pm

Dear Chamara,

There are 2 types of radii which you specify in case of "analytical_curvature": The initial radius of the nucleus, and the critical radius.

The initial radius just defines whether you get a "small" grain, consisting of a single grid cell with a fraction corresponding to a sphere with this radius, or a big one with sharp interface (r>Δx). This behaviour is independent from the choice of the model.

The critical radius is required only in case of "analytical_curvature" and defines the initial curvature contribution. If this value is bigger than Δx, you get a correspondingly small curvature contribution. Additionally, curvature reduction to this value is also performed after the grain reached big size, so that it can continue growing even for very small values of Δx.

Thus, both radius values can be bigger than Δx, although you typically don't want that for the initial grain radius (if it is not a single-phase simulation like in case of recrystallisation). Indeed, it is a specific advantage of the analytical curvature model that you are allowed to define rcrit>Δx in order to permit nucleation with low undercooling in high resolution simulations.

Bernd

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Re: Simulation of solidification of Gamma prime alloy during SLM process

Post by CharMIC » Thu Jun 20, 2019 2:25 pm

Hi Bernd,

Thaks for the explanation. reason for asking this is that as you already know, i have grid spacing of 5nm and S/L intefacial energy of 2.8E-05. When I defined initial radius of 1nm and a critical radius of 1µm, the grain is disappearing very quickly,as soon as the simulation stats. then I increase the initial radius to 4nm. But the grain vanishes.

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