Dear All,
Good day. I have been working on the solidification of an alloy (Al-Mg-Zr) by LPBF process. For simulating the growth of columnar grains, a thermal gradient of 1x10^5 K/cm and a cooling rate of 1x10^6 K/s was applied. I have used the mobility database MOBAL5 along with TCAL7. The following results were obtained, but I also observed some ‘error’ messages towards the end of the solidification.
I have the following questions:
1) How do I fix the ‘error’ messages towards the end of simulations and if there are any more corrections required? How can I validate this structure?
2) How do I simulate the growth of equiaxed grains, since in Addalloy the equiaxed grains are formed due to the nucleation by Al3X precipitates, so which phase and phase interactions do I need to consider? I tried the simulation using Al3X phase (Al3X phase is only available through TCAL7 and not in MOBAL5 database) but couldn’t achieve any results. Is there any example I can refer to for this case?
Thanks. Best Regards
Desai
Solidification of Al-mg alloy in LPBF process.
Solidification of Al-mg alloy in LPBF process.
Last edited by Desai on Tue Jan 25, 2022 3:15 pm, edited 1 time in total.
Re: Solidification of Addalloy in LPBF process.
Dear Desai,
Welcome to the MICRESS Forum.
The warnings about "Demixing" of Zr demonstrates that your alloy does not behave like a dilute alloy (at least in the segregated regions at the bottom), and solute interactions lead to a pseudo-miscibility gap when using the "multi-binary" extrapolation scheme. The solution is switching to the "diagonal" extrapolation scheme, which you activate by putting the keyword "diagonal" in an extra line in the "Numerical Parameter" section of the concentration solver. This potentially also solves the other error messages which you present.
Another source of numerical problems could be neglecting potential secondary phases, which could lead to extreme and unrealistic segregation. You should check with Thermo-Calc whether single-phase solidification is expected or not (using the Scheil module).
Further hints:
- I guess that increasing spatial resolution by a factor of 2 or 3 would considerably improve your results
- Currently you do not do any updating of thermodynamic data during run time because the intervals you use are 0.1 s. You should reduce this time interval by at least 3-4 orders of magnitude to match the time-scale of your simulation
Best wishes and good luck
Bernd
Welcome to the MICRESS Forum.
The warnings about "Demixing" of Zr demonstrates that your alloy does not behave like a dilute alloy (at least in the segregated regions at the bottom), and solute interactions lead to a pseudo-miscibility gap when using the "multi-binary" extrapolation scheme. The solution is switching to the "diagonal" extrapolation scheme, which you activate by putting the keyword "diagonal" in an extra line in the "Numerical Parameter" section of the concentration solver. This potentially also solves the other error messages which you present.
Another source of numerical problems could be neglecting potential secondary phases, which could lead to extreme and unrealistic segregation. You should check with Thermo-Calc whether single-phase solidification is expected or not (using the Scheil module).
Further hints:
- I guess that increasing spatial resolution by a factor of 2 or 3 would considerably improve your results
- Currently you do not do any updating of thermodynamic data during run time because the intervals you use are 0.1 s. You should reduce this time interval by at least 3-4 orders of magnitude to match the time-scale of your simulation
Best wishes and good luck
Bernd
Re: Solidification of Al-mg alloy in LPBF process.
Dear Bernd,
Thank you for your quick response and the answers. I have applied the suggested solutions.
However, towards the end of the simulation, some error messages were displayed.
How do I correct these? Thank you.
Thank you and Best Regards,
Desai.
Thank you for your quick response and the answers. I have applied the suggested solutions.
However, towards the end of the simulation, some error messages were displayed.
How do I correct these? Thank you.
Thank you and Best Regards,
Desai.
Re: Solidification of Al-mg alloy in LPBF process.
Dear Desai,
You need to put the "diagonal" keyword before the "no_stoichio" (which is the end of the free-style ("terse") input region). This is the reason why you still have these "demixing" messages, and probably also the cause of the others.
I am wondering why you did not get any error message during input already...
Bernd
You need to put the "diagonal" keyword before the "no_stoichio" (which is the end of the free-style ("terse") input region). This is the reason why you still have these "demixing" messages, and probably also the cause of the others.
I am wondering why you did not get any error message during input already...
Bernd