High computation time and other questions
Posted: Mon Oct 26, 2020 2:07 pm
Dear Bernd,
I have performed simulations of austenite formation in a Fe-0.67 wt% C -1.15 wt% Mn steel during heating at 1 K/s. The starting microstructure consists of pearlite and 9% of pre-eutectoid ferrite. I used a low grid size (5 nm) to resolve the fine cementite lamella.
The simulation was run with Thermo-calc coupling: the GES file was derived using Thermo-calc version 2020a (TCFE9 and MOBFE4).
The initial concentration was set as equilibrium 2. The value of ferrite composition at 973 K was derived by Thermo-calc (0.012 wt% C, 0.76 wt % Mn) (see the driving file PearliteDiss_TQpear_1Cs-1_Portion1_red1_in).
My first simulation run without problems but it was very slow (see the log file PearliteDiss_TQpear_1Cs-1_Portion1_red1_log.txt).
• Could you please suggest any change in the driving file to decrease the time step?
Besides, when I saw the microstructure after 0.49 s (see the file PearliteDiss_TQpear_1Cs-1_Portion1_red1_phas_0.49s. png) I found that only one of the two austenite nuclei, which MICRESS set in the microstructure, grew (see the file PearliteDiss_TQpear_1Cs-1_Portion1_red1_phas_0.03s. png).
• Are there any reasons for the different behaviour of the two austenite grains?
In the second simulation, I increased the initial temperature from 1003 K to 1015 K to better fit some experimental data (see the driving file PearliteDiss_TQpear_1Cs-1_Portion1_red2_in.txt).
In this case, MICRESS set only one nucleus (instead of two in the previous simulation) and this nucleus did not grow, despite the high undercooling (3084.6 K!!!). I suppose that this was a consequence of the change in the linearisation parameters of the phases BCC/FCC by increasing the T0 of 12 K but I was not expecting such a big change(see the log filePearliteDiss_TQpear_1Cs-1_Portion1_red2_log.txt).
Then I run the third simulation by changing the setting of the initial concentration from “equilibrium 2” to “from file”.
The files for the concentration of Mn and C were derived by the initial concentration maps of the previous simulation; all the other settings have remained unchanged.
In this case, the relative fraction of the ferrite and cementite phase changes after the first step, before the austenite nucleation (see PearliteDiss_TQpear_1Cs-1_Portion1_red3_tabf.txt).
• What is the reason for the variation of the relative fraction of ferrite and cementite?
Also after the nucleus was set, the following error message appeared
trying hard phases 2 1 level: 4 zp= 115196 error= 3….
……………..
……………..
(see the PearliteDiss_TQpear_1Cs-1_Portion1_red3_log.txt).
Finally, I run the fourth simulation by changing the temperature at which the initial equilibrium is calculated (see the driving file PearliteDiss_TQpear_1Cs-1_Portion1_red4_in); the error message disappeared but no nuclei were set!
Please let me know which other input/output files you will need for helping me in defining the correct driving file for simulating the pearlite to austenite formation.
Best Regards
Pina
I have performed simulations of austenite formation in a Fe-0.67 wt% C -1.15 wt% Mn steel during heating at 1 K/s. The starting microstructure consists of pearlite and 9% of pre-eutectoid ferrite. I used a low grid size (5 nm) to resolve the fine cementite lamella.
The simulation was run with Thermo-calc coupling: the GES file was derived using Thermo-calc version 2020a (TCFE9 and MOBFE4).
The initial concentration was set as equilibrium 2. The value of ferrite composition at 973 K was derived by Thermo-calc (0.012 wt% C, 0.76 wt % Mn) (see the driving file PearliteDiss_TQpear_1Cs-1_Portion1_red1_in).
My first simulation run without problems but it was very slow (see the log file PearliteDiss_TQpear_1Cs-1_Portion1_red1_log.txt).
• Could you please suggest any change in the driving file to decrease the time step?
Besides, when I saw the microstructure after 0.49 s (see the file PearliteDiss_TQpear_1Cs-1_Portion1_red1_phas_0.49s. png) I found that only one of the two austenite nuclei, which MICRESS set in the microstructure, grew (see the file PearliteDiss_TQpear_1Cs-1_Portion1_red1_phas_0.03s. png).
• Are there any reasons for the different behaviour of the two austenite grains?
In the second simulation, I increased the initial temperature from 1003 K to 1015 K to better fit some experimental data (see the driving file PearliteDiss_TQpear_1Cs-1_Portion1_red2_in.txt).
In this case, MICRESS set only one nucleus (instead of two in the previous simulation) and this nucleus did not grow, despite the high undercooling (3084.6 K!!!). I suppose that this was a consequence of the change in the linearisation parameters of the phases BCC/FCC by increasing the T0 of 12 K but I was not expecting such a big change(see the log filePearliteDiss_TQpear_1Cs-1_Portion1_red2_log.txt).
Then I run the third simulation by changing the setting of the initial concentration from “equilibrium 2” to “from file”.
The files for the concentration of Mn and C were derived by the initial concentration maps of the previous simulation; all the other settings have remained unchanged.
In this case, the relative fraction of the ferrite and cementite phase changes after the first step, before the austenite nucleation (see PearliteDiss_TQpear_1Cs-1_Portion1_red3_tabf.txt).
• What is the reason for the variation of the relative fraction of ferrite and cementite?
Also after the nucleus was set, the following error message appeared
trying hard phases 2 1 level: 4 zp= 115196 error= 3….
……………..
……………..
(see the PearliteDiss_TQpear_1Cs-1_Portion1_red3_log.txt).
Finally, I run the fourth simulation by changing the temperature at which the initial equilibrium is calculated (see the driving file PearliteDiss_TQpear_1Cs-1_Portion1_red4_in); the error message disappeared but no nuclei were set!
Please let me know which other input/output files you will need for helping me in defining the correct driving file for simulating the pearlite to austenite formation.
Best Regards
Pina