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Re: Simulation of solidification of Gamma prime alloy during SLM process
Posted: Thu Jun 20, 2019 2:42 pm
by Bernd
Then, curvature seems not to be the problem, and you should have a look on the driving force...
Re: Simulation of solidification of Gamma prime alloy during SLM process
Posted: Thu Jun 20, 2019 2:48 pm
by CharMIC
I checked in .TabLin. I only see negative dG values. Strange thing, before disappearing, I see a message in .scr file that grain reached full size. after that message then it shows "phase 1 disappeared".
Initial equlibrium is checked at 1653K. But I simulation I start at a temperature of 1651K
Re: Simulation of solidification of Gamma prime alloy during SLM process
Posted: Thu Jun 20, 2019 6:26 pm
by Bernd
Hi Chamara,
It could also be a numerical problem. Cutting down curvature is a quite crude procedure, especially if you take into account that the term which is cut consists of both, the stabilisation and the curvature contribution. Therefore, you should not cut more than necessary, and a critical radius of 1 µm means cutting almost completely!
I would try setting the critical radius as small as possible...
Bernd
Re: Simulation of solidification of Gamma prime alloy during SLM process
Posted: Fri Jun 21, 2019 9:20 am
by CharMIC
I have tried with small critical radius. Then the nucleation would start to grow in an undercooling > 15 K. Deviating this amount from equilibrium is OK?
Re: Simulation of solidification of Gamma prime alloy during SLM process
Posted: Fri Jun 21, 2019 11:14 pm
by Bernd
This depends on the circumstances. Is it "nucleation" of the primary dendrite in a unit cell model (isothermal cross-section)? Then, undercooling should match the 3D-tip undercooling which can be in this order of magnitude...
Bernd
Re: Simulation of solidification of Gamma prime alloy during SLM process
Posted: Mon Jun 24, 2019 10:26 am
by CharMIC
Hi Bernd,
Yes simulation is 2D isothermal simulation. Then probably this level of undercooling is OK.
Re: Simulation of solidification of Gamma prime alloy during SLM process
Posted: Wed Jun 26, 2019 2:20 pm
by CharMIC
Hi Bernd,
Small question. In experiments, the eutectic (in the intercellular area) γ' has a size around 50nm. But in PF simulations the size I get is more than 100nm. IS this related to precipitation and growth of γ' phase in simulation much earlier than in experiments?
Re: Simulation of solidification of Gamma prime alloy during SLM process
Posted: Wed Jun 26, 2019 7:41 pm
by Bernd
Hi Chamara,
This could be the case. However, it could also be just the density of nucleation which you can set by choosing a shield or nucleation distance, a checking frequency, or a critical undercooling. Due to the lack of physical nucleation models, the size and density of precipitates needs to be calibrated in the simulation...
Bernd
Re: Simulation of solidification of Gamma prime alloy during SLM process
Posted: Fri Jun 28, 2019 10:42 am
by CharMIC
Hi Bernd
I get this error message when the remaining liquid phase change to gamma phase. I only get it one time. Since it is one time is it ok to ignore it?
- Serious error.PNG (40.97 KiB) Viewed 28630 times
Re: Simulation of solidification of Gamma prime alloy during SLM process
Posted: Mon Jul 01, 2019 1:14 pm
by Bernd
Hi Chamara,
yes, you are right. Changing the identity of a phase is a quite "strong" procedure, and all equilibria with that new phase have to be recalculated at the given composition of the old phase - this always creates some errors. If they occur only once, everything is ok!
Bernd