CSL boundaries Sigma3 and Sigma27 have overlap

[Weiwei Li]

Please be as detailed as possible, explain what you want to do, what kind of data you are using. Attaching simplified code and data is always useful. Click the the button { } to inline code and finally remove these lines before posting :)

Hi,

I am using pure Copper and am looking to do a CSL grain boundary analysis specifically on the Sigma 3, 9, and 27 boundaries. The following is my code:

{       

        minGB = input('Minimum misorientation angle for a GB to exist?: ');

        b = input('Minimum number of indexed points to create a grain?: ');

        [grains,ebsd.grainId] = calcGrains(ebsd('indexed'),'angle',minGB*degree);

        selected_grains = grains(grains.grainSize > b);

        ebsd2 = ebsd(selected_grains);

        [grains,ebsd2.grainId] = calcGrains(ebsd2('indexed'),'angle',minGB*degree);

        grains = smooth(grains,1);

        

        gB = grains.boundary('Copper','Copper');

        plot(gB,'lineColor','black','linewidth',1.5,'DisplayName','HAGB')

%CSL boundaries defined based on the Palumbo-Aust criterion

        gB3 = gB(gB.isTwinning(CSL(3,ebsd2.CS),6*degree));

        gB9 = gB(gB.isTwinning(CSL(9,ebsd2.CS),2.4*degree));

        gB27 = gB(gB.isTwinning(CSL(27,ebsd2.CS),0.96*degree));

        hold on;

        plot(gB27,'lineColor','r','linewidth',1.5,'DisplayName','CSL 27');

        plot(gB9,'lineColor','b','linewidth',1.5,'DisplayName','CSL 9');

        plot(gB3,'lineColor','g','linewidth',1.5,'DisplayName','CSL 3');

}

Based on which order I write the last 3 lines of my code as shown in the script above, I will get a different labeling of grain boundaries according to the attached figure. Is this a problem in how the Sigma27 boundary is defined in MTEX? I know that in an FCC crystal, it should be defined as 27a = 31.58degrees and 27b = 35.42degrees, which are completely different than the Sigma3 boundary which is a 60degree misorientation. Despite this, the Sigma27 boundary is replacing some of the Sigma3 boundary in my map.

My crystal symmetry is.

{

CS = {... 

  'notIndexed',...

  crystalSymmetry('m-3m', [3.6144 3.6144 3.6144], 'mineral', 'Copper', 'color', 'light blue')};

}

Thank you

Weiwei

[Ralf Hielscher]

Dear Weiwei,

thank you for reporting this issue. The problem is that MTEX wrongly generates not only the 2 correct CSL 27 misorientations you mentioned but also includes the CSL 3 misorientation. you can fix this by removing this misorientation

csl27 = CSL(27,ebsd2.CS)
csl27(3) = []

The last line removes the wrong CSL 27 misorientation.

Now do

gB27 = gB(gB.isTwinning(csl27,0.96*degree));

I hope this helps,

Ralf.

[Weiwei Li]

Many thanks Ralf!