Heat Treatment simulation of Ni-alloy

solid-solid phase transformations, influence of stresses and strains
CharMIC
Posts: 196
Joined: Mon Aug 21, 2017 5:01 pm
anti_bot: 333

Re: Heat Treatment simulation of Ni-alloy

Post by CharMIC » Tue Jun 05, 2018 6:35 am

Hej Bernd,

In a heat treatment simulation, what temperature should be set for the initial equilibrium calculation?

Also should we take out the parameter for the liquid phase from Dri file.

I use restart with structure only option to read the initial microstructure. Initial microstructure only consist Gamma and Laves phase. No liquid is present in the initial microstructure.

BR
Chamara

Bernd
Posts: 1084
Joined: Mon Jun 23, 2008 9:29 pm

Re: Heat Treatment simulation of Ni-alloy

Post by Bernd » Wed Jun 06, 2018 11:17 pm

Hej Chamara,

When you perform a heat treatment simulation, the best option is to start with the same temperature where the previous simulation (i.e. solidification) was stopped. Then, the temperature for initialisation should be this same temperature. If you cannot start with the same temperature from the previous simulation, it is better in most cases at least to take the end temperature of the previous simulation as initialisation temperature.
However, in some cases it may be necessary to choose yet another temperature for initialisation, if the initial equilibrium otherwise fails.

If there is no liquid phase present anymore (and it should be like that!), you can remove all phase interactions between liquid and other phases. This is not necessary but simplifies your input file. Then, also no link to the database and no diffusion data need to be defined (at least if you use "terse" input).

Bernd

CharMIC
Posts: 196
Joined: Mon Aug 21, 2017 5:01 pm
anti_bot: 333

Re: Heat Treatment simulation of Ni-alloy

Post by CharMIC » Thu Jun 07, 2018 9:10 am

Thanks Bernd

CharMIC
Posts: 196
Joined: Mon Aug 21, 2017 5:01 pm
anti_bot: 333

Re: Heat Treatment simulation of Ni-alloy

Post by CharMIC » Fri Jun 22, 2018 10:03 am

Hej Bernd,

What temperature value should be specify under following when you perform a Heat Treatment (HT) simulation with "restart structure only"

# Temperature at which the initial equilibrium
# will be calculated? [K]

Should it be the same temperature as HT?

BR
Chamara

Bernd
Posts: 1084
Joined: Mon Jun 23, 2008 9:29 pm

Re: Heat Treatment simulation of Ni-alloy

Post by Bernd » Fri Jun 22, 2018 5:44 pm

Hi Chamara,

What is the difference to your last question? Do I miss something?

Bernd

CharMIC
Posts: 196
Joined: Mon Aug 21, 2017 5:01 pm
anti_bot: 333

Re: Heat Treatment simulation of Ni-alloy

Post by CharMIC » Mon Jun 25, 2018 7:20 am

Hej Bernd,

Sorry for the post. I could not see the post for some reason. I remember that I posted it before.

I have another question.

Some times in the HT simulation when I defined "database local" under phase diagram between gamma and Laves, I get "trying hard phase errors".

But when I change local description to global or globalF, I am not getting any errors. What is the reason for this? Does this affect the results significantly?

BR
Chamara

Bernd
Posts: 1084
Joined: Mon Jun 23, 2008 9:29 pm

Re: Heat Treatment simulation of Ni-alloy

Post by Bernd » Mon Jun 25, 2018 9:55 am

Hi Chamara,

When you use "local" linearisation, a set of linearisation parameters is calculated for every interface cell. For this, local compositions (or averaged along the gradient if averaging of the driving force is specified) are used which typically show a higher variance as compared to the average for the whole grain interface ("global") or phase interface ("globalG"). Correspondingly, the probability to encounter numerical problems is higher.
Apart from the general characteristics of globally averaged linearisation (i.e. the question whether it makes sense to use a global average, or whether there are strong gradients in composition or temperature), there should be no significant differences in the accuracy of the results. In some cases it can be even more exact to use more frequent global instead of less frequent local relinearisation...

Bernd

CharMIC
Posts: 196
Joined: Mon Aug 21, 2017 5:01 pm
anti_bot: 333

Re: Heat Treatment simulation of Ni-alloy

Post by CharMIC » Tue Jun 26, 2018 9:16 am

Thanks Bernd for the input.

Now I am trying to precipitate delta phase during the HT simulation. When I use "seed_density" model I get nucleation and simulation runs without any problem.

But when I use "seed_undercooling" model, during the first nucleation check I get the following massage and simulation stops. I have not come across this type of error before.

I would like to know the reason for this.

BR
Chamara
Attachments
error_seed_undercooling.JPG
error_seed_undercooling.JPG (48.67 KiB) Viewed 791 times

CharMIC
Posts: 196
Joined: Mon Aug 21, 2017 5:01 pm
anti_bot: 333

Re: Heat Treatment simulation of Ni-alloy

Post by CharMIC » Tue Jun 26, 2018 10:00 am

Hej Bernd,

I have another question.

The delta phase (Orthorhombic) in Alloy 718 has following relationship with the gamma matrix (Cubic).

{111}gamma||(010)delta and <110>gamma||[100]delta

When I calculate the relative angles its 54 and 45 degrees respectively. For simplicity lets take 45 degrees only.

The simulation domain dendrite growth direction is normal to the 2D domain (i.e 001 direction is coming out of the 2D domain). I want to know who should I define the orientation relationship for the new delta phase nuclei.

Should I defined them under nucleation parameters or misorientation parameters under phase interaction data or both.

I am bit confused here. Could you please help me with this.

BR
Chamara

Bernd
Posts: 1084
Joined: Mon Jun 23, 2008 9:29 pm

Re: Heat Treatment simulation of Ni-alloy

Post by Bernd » Tue Jun 26, 2018 12:40 pm

Hej Chamara,

To your first question:

As you can see in the verbose output for nucleation, MICRESS tries to set 111406 grains within this time step. In the nucleation routine, MICRESS tries to allocate space for these new grains in the interface list. The "iFacePointers3" is one of in all 9 fields which point to those parts of the interface list which correspond to a specific grain interaction - therefore they are allocated as field(noGrain,noGrain). As 8-bit integer, each of those fields would require ~100 Gb of memory!

Thus, you simply request to many seeds, which may be due to a too small shield distance or nucleation distance...

Bernd

Post Reply