Interfacial energy, morphology and triple junction angle

Exchange about the physics background, diffuse interface theory, etc..
mmendes
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Re: Interfacial energy, morphology and triple junction angle

Post by mmendes » Sun Feb 12, 2017 3:10 am

Dear Bernd,

Thanks again for your help!
I am still struggling to get the needle shape. I have been changing parameters, but many things are still unclear to me. I´ve read the manual and also looked for answers here in the forum, but I still do not fully undertand some behaviors. Therefore, I would highly appreciate if you could clafify the following points:
1) In the nucleation subroutine, when I set the min. and max. orientation angle of ferrite to a certain value (say, x), my .ori file shows an orientation of (90+y+x), where y is the rotation angle that I set to my gamma grain 1. In the attached file, for instance, I set x= y=40 expecting them to have a parent relation = 0, but eventually the phase 2 got an orientation= 80. I also tryed to set x=-35 and y=5 and in this case my .ori file showed orientation = 60 to phase 2 (90+5-35). Why does it happen? The code will always make this operation? Why is grain 1 rotation taken into account and not grain 2?
2) To try to fix the abovementioned "problem", I then, set the rotation of gamma grain 1 = 5, rotation of gamma grain 2= 40, max and min rotation of alpha = -90 and misorientation between low and high angle = 15. This way, I got the same orientation of ferrite and gamma grain 1 (5°), and a high misorientation between ferrite and gamma grain 2. Since I used antifaceted and parent relation, I was expecting to get the needle shape towards grain 2, but I couldn´t get this shape. The behavior I got was ferrite "round" grains growing only towards grain 2 (higher misorientation). Why the antifaceted model is not working in this case? How can I fix this problem?
Please, find below part of my input file. It there something wrong in the parameters preventing me to get the ferrite grains to grow as needles only into grain 2?
3) How can I make the needle grow in an "angular" direction? I tried to change the facet vector, but I no longer got the needle shape.

# Data for phase 2:
# -----------------
# [identical phase number]
# Simulation of recrystallisation in phase 2?
# Options: recrystall no_recrystall [verbose|no_verbose]
no_recrystall
# Is phase 2 anisotrop?
# Options: isotropic anisotropic faceted antifaceted
antifaceted
# Crystal symmetry of the phase?
# Options: none cubic hexagonal tetragonal orthorhombic
cubic
# Number of type of facets in phase 2
1
# kin. anisotropy parameter Kappa?
# only one value for all facets/phases
# 0 < kappa <= 1
0.3000000
# Number of possible orientations of a facet 1
1
# 1 -th normal vector facet 1 ? 3*
1.000000
0.000000
0.000000

....
# Grain input
# ===========
# Type of grain positioning?
# Options: deterministic random [deterministic_infile] from_file
deterministic
# NB: the origin of coordinate system is the bottom left-hand corner,
# all points within the simulation domain having positive coordinates.
# Number of grains at the beginning?
2
# Input data for grain number 1:
# Geometry?
# Options: round rectangular elliptic
round
# Center x,z coordinates [micrometers], grain number 1?
0.00000
31.0000
# Grain radius? [micrometers]
45.0000
# Shall grain 1 be stabilized or shall
# an analytical curvature description be applied?
# Options: stabilisation analytical_curvature
stabilisation
# Should the Voronoi criterion?
# Options: voronoi no_voronoi
voronoi
# Phase number? (integer)
1
# Rotation angle? [Degree]
5.00000000000000
# Input data for grain number 2:
# Geometry?
# Options: round rectangular elliptic
round
# Center x,z coordinates [micrometers], grain number 2?
62.0000
31.0000
# Grain radius? [micrometers]
45.0000
# Shall grain 2 be stabilized or shall
# an analytical curvature description be applied?
# Options: stabilisation analytical_curvature
stabilisation
# Should the Voronoi criterion?
# Options: voronoi no_voronoi
voronoi
# Phase number? (integer)
1
# Rotation angle? [Degree]
40.0000000000000

....
# Input for seed type 1:
# ----------------------
# Type of 'position' of the seeds?
# Options: bulk region interface triple quadruple [restrictive]
interface
# Phase of new grains (integer) [unresolved|add_to_grain]?
2
# Reference phase (integer) [min. and max. fraction (real)]?
1
# Substrate phase [2nd phase in interface]?
# (set to 1 to disable the effect of substrate curvature)
1
# maximum number of new nuclei 1?
50
# Grain radius [micrometers]?
0.00000
# Choice of growth mode:
# Options: stabilisation analytical_curvature
stabilisation
# min. undercooling [K] (>0)?
50.000
# Determination of nuclei orientations?
# Options: random randomZ fix range parent_relation
parent_relation
# Minimal value of rotation angle? [Degree]
-90.00
# Maximal value of rotation angle? [Degree]
-90.00
....

# Data for phase interaction 1 / 2:
# ---------------------------------
# Simulation of interaction between phase 1 and 2?
# Options: phase_interaction no_phase_interaction identical phases nb
# [standard|particle_pinning[_temperature]|solute_drag]
# | [redistribution_control] or [no_junction_force|junction_force]
phase_interaction redistribution_control
# 'DeltaG' options: default
# avg ... [] max ... [J/cm**3] smooth ... [degrees] noise ... [J/cm**3]
avg 0. smooth 45
# I.e.: avg +0.00
# Type of surface energy definition between phases 1 and 2?
# Options: constant temp_dependent
constant
# Surface energy between phases 1 and 2? [J/cm**2]
# [max. value for num. interface stabilisation [J/cm**2]]
2.0E-5
# Type of mobility definition between phases 1 and 2?
# Options: constant temp_dependent dg_dependent thin_interface_correction [fixed_minimum]
constant
# Kinetic coefficient mu between phases 1 and 2 [ min. value ] [cm**4/(Js)] ?
1.10000E-05
# Shall misorientation be considered?
# Options: misorientation no_misorientation [transition LAB/HAB in degree]
misorientation 15
# Input of the misorientation coefficients:
# Modification of surface energy for low angle boundaries
# Options: factor Read-Shockley
Read-Shockley
# Modification of the mobility for low angle boundaries
# Options: factor Humphreys [min_reduction + parameters B and N (default: min_red=0. B=5.0 N=4.0)]
Humphreys
# Is interaction isotropic?
# Optionen: isotropic anisotropic
anisotropic
# This anisotropic interaction is not yet implemented.
# Instead: isotropic-faceted
# static anisotropy coefficient of facet 1 (0 < a <= 1, 1=isotrop, 0 not defined)
0.15
# kinetic anisotropy coefficient of facet 1 (0 <= a <= 1, 1=isotrop)
0.195

Looking forward to hearing back from you.
Thank you so much!
Attachments
image1.jpg
image1.jpg (69.53 KiB) Viewed 992 times

Bernd
Posts: 1074
Joined: Mon Jun 23, 2008 9:29 pm

Re: Interfacial energy, morphology and triple junction angle

Post by Bernd » Mon Feb 13, 2017 12:41 am

Dear mmendes,

I am not sure whether I completely understand your problems. I will give you a tentative answer, and try to involve janine, who knows much more details about the orientation and misorientation stuff, if necessary.

1.) When you chose "parent_relation" in the nucleation input, all orientations you input afterwards are misorientations. Thus, if you want a parent relation of 0° you should put 0 as minimum and 0 as maximum. The parent grain will be chosen automatically depending on which grain fraction is bigger at the place nucleation occurs.

2.) When you choose -90° as minimum and -90° as maximum, like in your case, this would be the same as 0° if the cubic symmetry applied. However, as far as I know, the facet (and antifacet) model does not automatically add all other facets even if you specify cubic symmetry. That means that you really have a misorientation of -90° regarding your facet orientation which would explain that you do not get the expected.

3.) While needle growth along the grid direction is relatively simple, needles growing in oblique directions require a quite high grid resolution in order to overcome the unwanted anisotropy of the numerical grid. It may also be helpful to increase interface anisotropy coefficients, use interface stabilisation (optional parameter in same line with interface energy) or averaging of driving force.

Bernd

mmendes
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Re: Interfacial energy, morphology and triple junction angle

Post by mmendes » Mon Feb 13, 2017 8:46 pm

Dear Bernd,

I tried to set the parent relation to 0° as you suggested, but still without success. The alpha grains grow faster into my gamma grain 2, but no needle shape is observed (like when I set -90°). :| Strange that, I just changed that parameter compared to the last simulation image I posted, and I no longer got the needle. Could you, please, check with Janine why this is still happening?

Thank you so much!

Bernd
Posts: 1074
Joined: Mon Jun 23, 2008 9:29 pm

Re: Interfacial energy, morphology and triple junction angle

Post by Bernd » Mon Feb 13, 2017 11:51 pm

Dear mmendes,

Can you please attach the complete driving file or send it by PM (including other needed files like .ges5 etc.)? Otherwise it will be difficult to find out...

Bernd

Bernd
Posts: 1074
Joined: Mon Jun 23, 2008 9:29 pm

Re: Interfacial energy, morphology and triple junction angle

Post by Bernd » Thu Feb 16, 2017 1:02 pm

Dear mmendes,

After digging more into the topic, I remembered that there is a new example in MICRESS Version 6.3 called "Gamma_Alpha_FeC_Acicular" which should be very interesting for you. It uses tetragonal anisotropy for simulation of needles, but can easily be transcribed for using the antifaceted model (see attachment).

Furthermore, the new MICRESS version includes a new feature for defining special orientation relations in the misorientation model which is extremely helpful in your case. Therefore, I strongly recommend to switch to Version 6.3 which is also needed to run the attached example.

Anyway, I think the main problem with your input file is that you use specific misorientation models (Humphrey, Read Shockley) which are suitable for low angle grain boundaries but not for your case: you need to stop the ferrite from growing into the wrong grain, i.e. to disfavor high angle phase boundaries. Currently you disfavor the low angle boundaries which (as far as I understand) you intend to favor. In the old MICRESS version, you instead could (indirectly) use a factor model to favor low angle phase boundaries and correspondingly correct the normal values of the interface mobility and energy. However, the new MICRESS version is much smarter with using special orientation relations.

The question whether it is better to use tetragonal or antifaceted anisotropy of ferrite to obtain needles is still open. You can try both and select the one which behaves better for your case. My experience is that the antifaceted model better allows for restricting lateral growth of the needles. Static anisotropy should be switched off (anisotropy coefficient 1.0). However, for simulating stable needles or plates (i.e. those which would not vanish during heat treatments through ripening), the tetragonal model could perhaps be better. Please make your own experiences and tell us here in the forum.

Bernd
Attachments
Gamma_Alpha_FeC_Acicular_b.dri
(24.78 KiB) Downloaded 108 times

mmendes
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Re: Interfacial energy, morphology and triple junction angle

Post by mmendes » Tue Jul 11, 2017 12:28 am

Hi Bernd,

Is it possible to use the elastic strain anisotropy instead of interfacial energy anisotropy to simulate Widmanstatten microstructure in Micress? I read a paper in which the former parameter was used and the result is way more realistic than when using the later one. If that is possible, do I need to have an extra license for that?

Thank you! :)

Bernd
Posts: 1074
Joined: Mon Jun 23, 2008 9:29 pm

Re: Interfacial energy, morphology and triple junction angle

Post by Bernd » Tue Jul 11, 2017 12:02 pm

Dear mmendes,

Yes, there is a separate elastic module which needs its own licence. Whether the results are more realistic I cannot say - probably yes, because the closer you get to real physics the more realistic results can be expected. However, we do not have any own experiences in the field of Widmanstätten microstructures so far...

In case you want to go for that, please ask Georg Schmitz (G.J.Schmitz@micress.de) for a quotation in case you haven't already a valid licence for the elastic module.

Could you share the paper reference?

Bernd

mmendes
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anti_bot: 333

Re: Interfacial energy, morphology and triple junction angle

Post by mmendes » Tue Jul 11, 2017 5:38 pm

Thanks for answering Bernd!

I will contact Georg for the quote.
Although you are not so experienced in Widmanstatten microstructures, do you think I will be able to easily simulate the plate-like morphology using the elastic module package in Micress?

This is the paper I meant: http://www.sciencedirect.com/science/ar ... 8815306757

Bernd
Posts: 1074
Joined: Mon Jun 23, 2008 9:29 pm

Re: Interfacial energy, morphology and triple junction angle

Post by Bernd » Tue Jul 11, 2017 10:04 pm

Dear mmendes,

Thanks for the link!
I have really no idea whether it could work, and would be rather skeptical: In the paper they work with very fine resolution at the nano-scale, and they have a different phase-field model. However, I also cannot rule out that it works...

Bernd

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