Grain orientation/ Misorientation/MTRs

[David Harra]

HI everyone hope you are all well. I have a few questions if anyone can help out.

I have segmented my grains, albeit not the best grain reconstruction as my EBSD scan was very coarse. I am using a Titanium sample (mostly all alpha grains)

Based on my grain segmentation I  have Inverse pole figures (IPF)  showing the distribution of grain orientations. The questions I haver is:

1) Is there a way to see how many grains from my sample are favoured to a specific orientation with their grain sizes.? 

For example, within my sample how many grains are favoured in the 0001 direction and for those grains in that direction, what are their sizes?

2) Is the same idea possible to achieve with grain misoreintations ?  How many grains and their sizes lie within certain thresholds, for example, 5 degrees up to 60 degrees?

3) I have also used Dream3d to generate the pole figures. I have watched some videos on this and I am still struggling to  understand how I can describe the texture of my sample just by looking at these pole figures  I have posted an image below if someone is able to explain  how to constructively explain this example. These pole figures are generated based on the 001 reference direction. (Alpha grains Titanium) 

4) When we segment our grains, each grain has its own feature ID. Can these grains be grouped into larger features  (Macrozones /MTRs)  that would have MTR Ids so I can tell what grains belong to a specific MTR? I could then tell  what grains belong to each MTR and the orientation of that MTR.

Thanks

Dave :) 

[Anthony Rollett]

Hi David

You are basically asking about volume fractions obtained by integration in the Orientation Distribution over a “capture radius” for each orientation of interest (“texture component”) and area fractions for GBs in the Misorientation Distribution (analogous question).  At this point, you might want to do some background reading about texture and how to deal with it quantitatively; in addition to the Kocks/Tomé/Wenk or Engler/Randle books, my lecture notes should once again be visible on the web (search on “rollett texture 27750”).    

Your texture looks strongly sheared compared to typical ones but, again, you will need to compare to the literature.

Good luck!

Tony Rollett

On Sep 14, 2021, at 7:35 AM, David Harra <davidha...@gmail.com> wrote:

HI everyone hope you are all well. I have a few questions if anyone can help out.

I have segmented my grains, albeit not the best grain reconstruction as my EBSD scan was very coarse. I am using a Titanium sample (mostly all alpha grains)

Based on my grain segmentation I  have Inverse pole figures (IPF)  showing the distribution of grain orientations. The questions I haver is:

1) Is there a way to see how many grains from my sample are favoured to a specific orientation with their grain sizes.? 

For example, within my sample how many grains are favoured in the 0001 direction and for those grains in that direction, what are their sizes?

2) Is the same idea possible to achieve with grain misoreintations ?  How many grains and their sizes lie within certain thresholds, for example, 5 degrees up to 60 degrees?

3) I have also used Dream3d to generate the pole figures. I have watched some videos on this and I am still struggling to  understand how I can describe the texture of my sample just by looking at these pole figures  I have posted an image below if someone is able to explain  how to constructively explain this example. These pole figures are generated based on the 001 reference direction. (Alpha grains Titanium) 

<Screenshot (22).png>


4) When we segment our grains, each grain has its own feature ID. Can these grains be grouped into larger features  (Macrozones /MTRs)  that would have MTR Ids so I can tell what grains belong to a specific MTR? I could then tell  what grains belong to each MTR and the orientation of that MTR.

Thanks

Dave :) 

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<Screenshot (22).png>

[Joe Wendorf]

David,

I have had good results segmenting MTRs in my equiaxed Ti64 microstructures with the C-axis segmentation filter. Use a high tolerance around 10-15 degrees.

C-axis can also be used for some very simplified texture analysis. For example, calculate feature average c-axes in dream3d and then extract them from your .dream3d file with your favorite programming language (look up functions/libraries for working with the .h5 file format). Then, a simple dot product can be used to find the angle of the C-axis with a given direction. 

I definitely recommend following Tony's course on texture analysis, but maybe this C-axis trick can help you get started. They are a lot easier than working with full orientations.

Regards,

Joe

[Michael Jackson]

Also a word of caution that you fully understand and can document what you are doing but what DREAM.3D is doing when it finds orientations and “average” orientations. The determination whether an orientation falls into another group can produce results that are sometimes unexpected due to a group of the orientations being split by the Rodrigues space boundary. (Hard to explain in words, pictures are a big help here but I don’t have one at the moment.) I have consulted with several folks about this issue and how it arises with the C-Axis that texture analysis uses with no real satisfactory result.

 

https://github.com/imikejackson/EbsdLib/blob/b5867fc5634d21a70870a5dd29a517a36dc5ccfe/Source/EbsdLib/LaueOps/LaueOps.cpp#L189

 

that is as far as I got with some improved code.

 

Again, just a word of caution.

 

--

Michael Jackson | Owner, President

      BlueQuartz Software

[e] mike.j...@bluequartz.net

[w] www.bluequartz.net

 

 

David,

 

I have had good results segmenting MTRs in my equiaxed Ti64 microstructures with the C-axis segmentation filter. Use a high tolerance around 10-15 degrees.

 

C-axis can also be used for some very simplified texture analysis. For example, calculate feature average c-axes in dream3d and then extract them from your .dream3d file with your favorite programming language (look up functions/libraries for working with the .h5 file format). Then, a simple dot product can be used to find the angle of the C-axis with a given direction. 

 

I definitely recommend following Tony's course on texture analysis, but maybe this C-axis trick can help you get started. They are a lot easier than working with full orientations.

 

Regards,

 

Joe

 

On Tue, Sep 14, 2021, 4:35 AM David Harra <davidha...@gmail.com> wrote:

HI everyone hope you are all well. I have a few questions if anyone can help out.

 

I have segmented my grains, albeit not the best grain reconstruction as my EBSD scan was very coarse. I am using a Titanium sample (mostly all alpha grains)

Based on my grain segmentation I  have Inverse pole figures (IPF)  showing the distribution of grain orientations. The questions I haver is:

 

1) Is there a way to see how many grains from my sample are favoured to a specific orientation with their grain sizes.? 

For example, within my sample how many grains are favoured in the 0001 direction and for those grains in that direction, what are their sizes?

 

2) Is the same idea possible to achieve with grain misoreintations ?  How many grains and their sizes lie within certain thresholds, for example, 5 degrees up to 60 degrees?

3) I have also used Dream3d to generate the pole figures. I have watched some videos on this and I am still struggling to  understand how I can describe the texture of my sample just by looking at these pole figures  I have posted an image below if someone is able to explain  how to constructively explain this example. These pole figures are generated based on the 001 reference direction. (Alpha grains Titanium) 

4) When we segment our grains, each grain has its own feature ID. Can these grains be grouped into larger features  (Macrozones /MTRs)  that would have MTR Ids so I can tell what grains belong to a specific MTR? I could then tell  what grains belong to each MTR and the orientation of that MTR.

Thanks

Dave :) 

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