distinguish various twinning systems

[KKone121]

Hi!
I have introduced different twins such as {10-12},{10-11} in Mg alloys by compression.
I want to distinguish different kinds of twins in different colors and calculate the twin area fraction.
Help is appreciated, thank you.

[kilir]

Hi,
can you distinguish which part of the grain is the twin and which part is the host?
Cheers,
Rüdiger

[KKone121]

Hi, Rüdiger.
By referring to the examples of mtex, I can distinguish the twins and the host. It's hard that I can't distinguish between different twin types.
Kyle

[kilir]

Hi,
while I don't recall there's a section elaborating that, in any case, if you know the different twin laws, simply discriminate the boundaries accordingly e.g.

twinBoundary1 = gB(angle(gB.misorientation,twinlaw1) < 5*degree);
twinBoundary2 = gB(angle(gB.misorientation,twinlaw2) < 5*degree);

If you have some prior knowledge what is the host and what is the twin, you can then apply it to the neighboring grains of your twin boundaries. You'll get the unique grain ids from unique(twinBoundary.grainId,'row'), discreminite twin and host and compute the volume fraction from those.

Cheers,
Rüdiger

[KKone121]

Thanks for your kind suggestions, and I'm trouble in how to definition the twinning law of 11-21 twin now.
As described in , I have coded how to define 11-21 twin, but it always reports errors. The code is as follows, could u give me some suggestions?

twinning1 = orientation.map(Miller(0,1,-1,-2,CS),Miller(0,-1,1,-2,CS),Miller(2,-1,-1,0,CS),Miller(2,-1,-1,0,CS));
twinning2 = orientation.map(Miller(1,1,-2,1,CS),Miller(1,-1,2,-1,CS), Miller(1,-1,0,0,CS),Miller(-1,1,0,0,CS));

The error is Inconsitent pairs of vectors! The angle between u1, u2 and v1, v2 needs to be the same, but differs by 61.9451°. I think it may be a crystallographic knowledge, but without any ideas

[kilir]

How about
twinning2 = orientation.map(Miller(1,1,-2,1,CS),Miller(-1,-1,2,-1,CS), Miller(1,-1,0,0,CS),Miller(-1,1,0,0,CS)); ?

[KKone121]

That's a good idea, thanks for u, Rüdiger.

I would like to ask how I can calculate the twin area by using misorientation to distinguish different twins. In the Mtex merging grains section, it mentions using twins that occupy less than half of the total area for identification, but this does not seem to align with my situation.

Additionally, I have not found similar cases in Mtex regarding the use of the unique function 'unique(twinBoundary.grainId,'row')'. Could you please provide a more detailed explanation?

Thank you for your guidance.

Kyle

[KKone121]

Here is the code to supplement my original idea：
twin1fraction=sum(area(grains(isTwinning1)))/sum(area(grains)) * 100; twin2fraction=sum(area(grains(isTwinning2)))/sum(area(grains)) * 100;

[apedgaon]

@KKone121 @kilir, how do you construct the misorientation object for a twin? How do you know it is (11-21) twin and then how do you infer the right misorientation for it? I am also observing the twinning2 in my EBSD data but unsure which type of twin it is. The misorientation object seems to transform the twin plane (11-21) which doesn't seem logical.