MICRESS Forum

Hello

Dear Mr. Bernd,

I had this following problem in the results of one of the programe. Could you explain me the error here please?


Time t = 0.0000 s
CPU-time: 1 s
Current phase-field solver time step = 1.00E-05 s
Temperature at the bottom = 1120.0 K
Temperature gradient = 0.00000 K/cm
Fraction of phase 0 : 1.00000
Fraction of phase 1 : 0.00000
Fraction of phase 2 : 0.00000

# Minimum undercooling for stable growth, seed type 2: 0.1876947 K [r=0.3750000 mic.]

Seed number 1 set at time t = 1.00E-02 s
----------------------------------------
in the bulk
Phase: 2 (BCC_A2)
Seed type: 2 (5: 1/1)
Temperature at the bottom = 1118.8 K
Undercooling = 206.93 K
Grain number = 1
not converged, error= 1 in interface 0 2
try harder! Error = 1
not converged, error= 1 in interface 0 2
try harder! Error = 1
not converged, error= 1 in interface 0 2
try harder! Error = 1

Thanks
Raghav

Dear Raghav,

This type of errors occur if there is a convergence problem in the calculation of the quasi-equilibrium – in your case between the phases 0 and 2. It can happen for example if the system is very far from local equilibrium and ranges in the thermodynamic database are accessed which are not correctly modeled (due to a lack of experimental data in those metastable regions).
In your case that is (without knowing more about what you are trying to do) most probably caused by the nucleation undercooling of more than 200 K for the BCC phase. The error message should vanish if you increase the initial temperature such that BCC would nucleate with a lower undercooling.

Generally, the occurance of such an error does not necessarily mean that the results are wrong, as long as the messages are appearing only temporarily. Then the program was able to recover. Otherwise, it is necessary to change either the conditions (like the initial temperature) or the numerical parameters (e.g. interface mobility).

Bernd

Dear Mr. Bernd

Thank you for the satisfactory explanation.

Hello Mr. Bernd

Actually, this is a continuation of the work by Mr. Nico Steinert.

For the simulation concerning CuAl10Fe5Ni5, i used 2 phases namely FCC_A1 and BCC_A2.
The problem is simulations begins but i get no results absolutely, may be the problem lies with the
GES file (file used is the one sent by you couple of months earlier, CuAlFeNi.GES5) or
in the initial Linearisation data. I am not sure. What is your opinion?

Also, i made my own GES file but same problem appears.

Best regards
Raghav

Dear Raghav,

from the .log file one can see that nucleation of phase 2 is never checked, otherwise the linearisation data for the 0/2 interface would appear. This is only possible if no interface 0/1 is present at all as nucleation is performed on interfaces in this case (or any other error in the nucleation input is present which I cannot see...).
Initial grain setting of phase 1 is with radius 0, i.e. small grains with very little fraction are set. The initial linearisation data for the 0/1 interface show a positive driving force, which means that the small grains will melt away! Therefore, no interface is present any more when nucleation of phase 2 is checked...

The solution is to start at a lower temperature in order to avoid melting of phase 1. You should also remove the iterations for initialisation of the interfaces (0 instead of 10), because there are no sharp interfaces at the beginning, and - depending on the exact MICRESS version number - the small grains could even vanish.

Best regards

Bernd