New User Tutorials?

[MTEXNewbie]

Hi,

I am a new user of EBSD and EDS, so equally new to MTEX. I have just been trained and conducted EBSD data acquisition on metal samples. I went through the MTEX Documentation but everything went over my head.

I was wondering if the community can guide me on the analysis of the .ctf files I have obtained based on any step-by-step tutorials available? I can import the data but then what?

Thanks in advance!

[grandr...@gmail.com]

Try the manual at https://www.researchgate.net/publication/314280728_Getting_started_with_MTEX_for_EBSD_analysis

Let me know if you get stuck, and even though the section 'Validate your settings' is a bit troublesome it's really necessary to do.  In the past I've also had (multiple) issues with improper scale bar calibration on the SEM/EBSD system, so make sure you check that as well.

Once you've done that, try working through the tutorials (online or in the manual) to measure grain size, plot various maps etc.

And welcome to the forum!

Jessica

[MTEXNewbie]

Hi Jessica,

Thank you for the Manual, looks very promising.

I was wondering where can I find the Magnesium .ctf file to replicate the instructions in your manual.

Thanks.

[grandr...@gmail.com]

The .ctf file is your experimental data. You will export it from the EBSD software. It can be opened in notepad although these files are large and can take several mins to load. The .ctf file contains a header, and for each EBSD point measured the x-y position and the Euler angle at a minimum.     Try looking for a measurement file on the computer to practice with if you don't have your own data yet. Of course MTEX can take many different input EBSD files. Figure out what your acquisition software outputs. 

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[MTEXNewbie]

Okay I'll get a .ctf file from the Oxford Channel 5 EBSD software.

Could you please suggest me a book or simple tutorial on Miller indices, 3D vectors, Euler angle etc? I am new to materials science.

Thanks.

[grandr...@gmail.com]

For miller indexes the intro to materials book by Callister is popular (see below).  If you're new to materials  and working in metals I recommend chapters 3 (the structure of crystalline solids) , 4 (imperfections in solids) and 7 (strengthening mechanisms) at a minimum.  Take a look through and read over anything else relevant to your research.

For vector3D, this is just 3D Cartesian vectors, introduced in high school.

You will probably need to know;
-Euler angles, how to read a pole figure, how EBSD works as well

Easy introduction START HERE- work through the presentation/ animations at https://www.doitpoms.ac.uk/tlplib/crystallographic_texture/index.php

IF YOU LIKE MATH AND THE TECHNICAL ROUTE INSTEAD
For Euler angles, I recommend Randle and Engler (section 2.5).    It's more technical than Callister, so I recommend covering miller indices in Callister first, then reviewing your understanding in Randle.  Look at the EBSD map info, pole figures (chapter 5-representation of macrotexture data) and ODF in Randle as well, it will come up in your work almost certainly.

Test your understanding by manually entering a Euler angle into MTEX and observing the resulting pole figures.  Change the numbers and look again.  Do you understand what's going on with the material orientation?

What material and subject are you working in?  I may have more recommendations

Callister, W. Anderson, W. (Ed.) Materials Science and Engineering, An introduction John Wiley & Sons Inc, 2000.

Randle, V. & Engler, O. Introduction to Texture Analysis Macrotexture, Microtexture & Orientation Mapping Gordon and Breach Science Publishers, 2000

[MTEXNewbie]

Hi Jessica,

Your book suggestions have been a lot of help, thank you.

While I have started to understand the Orientation map, EBSD map etc., I am still kinda confused with Pole Figures.

How do I read EBSD Pole figures and what exactly does it entail? What do we understand from it?

Thank you.

[grandr...@gmail.com]

A pole figure is a way of representing texture that does not include spatial information (an EBSD map includes spatial information).
In other words, it is a method of representing the orientation of the material with relationship to the sample axes. One pole figure can represent a single point, or thousands of measurements. Look at the website below.  The pole figure shown is representing the orientation of that cubic material.  The example shown is a (100) pole figure, but you could do a (111) pole figure instead, or any other orientation.  The orientation you plot is usually listed in Miller indexes.  The axes x1 and x2 in the sample shown represent axes of the sample.  Try dragging the cube (representing the material) around and watching how the pole figure changes.

https://www.doitpoms.ac.uk/tlplib/crystallographic_texture/texture_representation.php

.  Instead of individual dots, you can also create a contoured pole figure, showing which regions have the most points., like the link below
https://en.wikipedia.org/wiki/Pole_figure#/media/File:MAUD-MTEX-TiAl-hasylab-2003-Liss.png

Jessica

[MTEXNewbie]

Hi Jessica,

I have done some progress, EBSD map plotting, grains, grain boundaries etc.

My question, is the inverse pole figure a 2D EBSD map colored according to the circle sector? Or it's a hemisphere as pole figure? Sorry for asking this, PF/IPF are not as straight forward as EBSD map.

Also, is it mandatory to calculate IDF first to obtain PF/IPF??

[grandr...@gmail.com]

Think about it this way, imagine that you take an ebsd map, and remove all the x-y spatial data leaving you a randomly ordered list of orientations.  One option for representing these orientations is to pick one axis in the unit cell (say [0001]), and for each orientation plot the angular relationship between that axis and the sample x and y and put a dot there. This is a pole figure.

On the other hand, for an inverse pole figure, we take these orientations, and instead pick a direction in the sample (say sample x).  We then determine the smallest shape (in orientation space) on which we can represent all possible angles.  Taking into account crystallographic symmetry, this is usually a wedge shape of some sort.  We then say, for this orientation which crystallographic axis is closest to the sample x direction?  Then we put a dot there.

We can color a 2D ebsd map in any way we want.  We can plot measures of the data quality (band contrast etc) OR we can plot measures of the orientation (misorientation to mean, euler angle etc) OR we can color an EBSD map by the grain sizes.  Lots of options.  The default is euler coloration I think.  What you are probably talking about here, is coloring an EBSD map by ipf coloration.  In the case where you choose to color the EBSD map by ipf x, each point of the EBSD map is colorised by how far it is from the sample x direction.

I have no idea what you mean by IDF, but if you meant ODF, the answer is no.  To plot a pole figure or IPF with points (ie one dot per measurement, which I refer to as a 'discrete' pole figure or data) no ODF calculation is necessary.  BUT if you want to contour your data (ie figure out the 'density' of points) then yes, ODF calculation is necessary first.

Jessica

[MTEXNewbie]

Hi Jessica,

That was very explanatory.

My material is Iron (Austenite). When I try to plot the 'discrete' IPF, I get this-

Code -

cs = crystalSymmetry('m-3m')

oM = ipdfHSVOrientationMapping(cs)

plot(oM)

But I get this figure from Oxford software -

What is the difference between these two, and how can I obtain the same planes (001), (101) and (111) in MTEX?

[ruediger Kilian]

Hi,
plot(oM,'xAxisDirection','West’) plots the figure the way you like to see it. Directions are equivalent.
Cheers,
Rüdiger

[grandr...@gmail.com]

FYI what you are plotting here is not your data it is the 'legend' of how things are coloured. 

Jessica

[MTEXNewbie]

Hi Jessica,

Yes, it is the legend of EBSD IPF map, I understood it from your explanation. :)

Since it is Cubic crystal, the negative component of the plane (-111) does not matter?

[grandr...@gmail.com]

That's correct, due to symmetry the two sections are equivalent.

[MTEXNewbie]

Hi Jessica,

Euler map, IPF map, ODF calculation, Pole figure done. I'm impressed by MTEX's capabilities! And also thank you and the group members.

I was wondering what does it mean by plotting fibers on a map, it is given in the documentation.

[MTEXNewbie]

Hi Jessica,

I noticed that ODF calculation requires grain calculation first. Is it really the case? How does grain calculation is related to plot contour PF?

[grandr...@gmail.com]

Grain calculation is not required before plotting contours.  For example try the below code (from manual section 'Pole figures with contoured data').  You must do odf calculation before plotting a contoured pole figure, since this changes the discreete measurements from EBSD data into a continuous function that can be contoured.

odf = calcODF(ebsd('Magnesium').orientations,'halfwidth',2*degree)
h=[Miller(0,0,1,cs)];
figure ; plotPDF(odf,h,'upper','projection','eangle');

[MTEXNewbie]

I have used the following code, could you please tell me how is it different from your code?

%% Plot Pole Figure

% set pole figure annotation

pfAnnotations = @(varargin) text([vector3d.X,vector3d.Y],{'TD','ND'},...

  'BackgroundColor','w','tag','axesLabels',varargin{:});

setMTEXpref('pfAnnotations',pfAnnotations);

% set font size

setMTEXpref('FontSize',22);

% contour PF

% compute grains, either use 'angle' or 'unitcell' for segmentation

[grains_rot,ebsd_rot.grainId] = calcGrains(ebsd_rot('indexed'),'unitcell');

% [grains,ebsd.grainId,ebsd.mis2mean] = calcGrains(ebsd,'angle',seg_angle*degree);

% Remove small grains with less than min_points indexed points

grains_rot = grains_rot(grains_rot.grainSize > min_points);

% Re-calculate grain model to cleanup grain boundaries with less than minimum index points

% used ebsd points within grains having the minimum indexed number of points (e.g. 5~10 points)

ebsd_rot = ebsd(grains_rot);

[grains_rot,ebsd_rot.grainId] = calcGrains(ebsd_rot('indexed'),'unitcell');

% [grains,ebsd.grainId,ebsd.mis2mean] = calcGrains(ebsd,'angle',seg_angle*degree);

% Due to the measurement grid, the grain boundaries often show a typical staircase effect.

% This effect can be reduced by smoothing the grain boundaries.

grains_rot = smooth(grains_rot,4);

% ODF Estimation

% compute optimal halfwidth from the meanorientations of grains

psi = calcKernel(grains_rot('Iron fcc').meanOrientation);

% load the orientation data into a variable

o = ebsd_rot('Iron fcc').orientations;

% compute the ODF with the kernel psi

odf = calcODF(o,'kernel',psi);

% define the crystal symmetry

csCPF = odf.CS;

% then define the pole figures to plot (no maximum)

h = [Miller(1,0,0,csCPF),Miller(1,1,0,csCPF),Miller(1,1,1,csCPF)];

% plot contour PF. add 'contourf' argument to fill colour contours, 'contour' to not

% fill, leave emtpty to get smooth gradient of colour (default).

figure

plotPDF(odf,h,'antipodal','projection','eangle','contourf',[0,0.25,0.50,0.75,1.00,1.25,1.50,1.75,2.00,2.25,2.50,2.75,3.00,3.25,3.50,3.75,4.00,4.25,4.50,4.75,5.00,5.25,5.50,5.75,6.00,6.25,6.50,6.75,7.00],'minmax')

CLim(gcm,'equal'); % set equal color range to all plots

mtexColorbar('location','southOutSide','title','M.U.D.')

Also, in your code, there seems to be an optimum halfwidth angle to be chosen, otherwise contour PF may look too coarse or too smooth. I there any standard value for halfwidth?

[grandr...@gmail.com]

The first part tells the code what labels to put on the pole figure (not included in my code).  Before they contour the pole figure, they plot grains, find all small grains, remove them, and smooth the boundaries.  This means that if the small grains contain useful information it will be removed.  Do you want to include the data from small grains?  Is this valuable or noise?  Something you will have to decide.  Finally the person customises the pole figure contours by defining the levels.

For the halfwidth there is no standard value, and what you choose can influence the presentation of your data significantly.  I found some interesting features that were only represented by a small fraction of my data - plotting as discrete points worked much better for me, your case may be completely different.  The person here though calculates the halfwidth based on the mean orientation, which could make it different for different pole figures if they come from different data sets.

Neither approach is wrong.  Mine is very simple, but if you're doing things for publication you probably want more detailed control of the pole figure presentation, as given in the example code you provided.  They commented this very nicely so I think you can customise it if you want.  But grain calculation is an option, and only makes a difference if you use it to filter the data like they did here.

[MTEXNewbie]

Thanks for the reply. I have used your code and varied the halfwidth angle from 2 to 15 degree and the resulting PF varies wildly. Whereas using mean orientation based calculation gives a generalized approach, I think I will use that.

I have one question, for 316L Austenite Steel I am plotting IPF map and PFs for fcc only, should I also plot everything for bcc as well? How can I do the combined fcc+bcc calculation for IPF map and PFs?

[Ralf Hielscher]

Dear MTEXNewbie,

please do not ask different questions within one thread. It makes other users extremely difficult to find answers to previously asked questions. For your current questions this means post it in a new thread and please rewrite it in an understandable manner. As it currently stands I have no idea what you want to compute and why you want to visualize something.

Ralf.

[MTEXNewbie]

Apologies if its creating confusion, I will post the question in a new thread.