Triple points

how to detect triple points

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Calculation of triple points
Index triple points by phase
Index triple points by grains
Index triple points by grain boundary
Boundary segments from triple points

Calculation of triple points

MTEX automatically computes triple points during grain reconstruction. They are acessable similarly to grain boundaries as an property of the grain list.

% import some EBSD data set
mtexdata small

% compute grains
grains = calcGrains(ebsd('indexed'));

% extract all triple points
tP = grains.triplePoints
 
tP = triplePointList  
 
 points   mineral 1   mineral 2   mineral 2
     15  Forsterite  Forsterite  Forsterite
      7  Forsterite  Forsterite   Enstatite
      4  Forsterite   Enstatite   Enstatite
      8  Forsterite  Forsterite    Diopside
     16  Forsterite   Enstatite    Diopside
      4  Forsterite    Diopside    Diopside
      2   Enstatite   Enstatite    Diopside
      1   Enstatite    Diopside    Diopside
     11    Diopside    Diopside    Diopside

Index triple points by phase

You may index triple points by the adjacent phases. The following command gives you all triple points with at least one phase being Forsterite

tP('Forsterite')
 
ans = triplePointList  
 
 points   mineral 1   mineral 2   mineral 2
     15  Forsterite  Forsterite  Forsterite
      7  Forsterite  Forsterite   Enstatite
      4  Forsterite   Enstatite   Enstatite
      8  Forsterite  Forsterite    Diopside
     16  Forsterite   Enstatite    Diopside
      4  Forsterite    Diopside    Diopside

The following command gives you all triple points with at least two phases being Forsterite

tP('Forsterite','Forsterite')
 
ans = triplePointList  
 
 points   mineral 1   mineral 2   mineral 2
     15  Forsterite  Forsterite  Forsterite
      7  Forsterite  Forsterite   Enstatite
      8  Forsterite  Forsterite    Diopside

Finaly, we may mark all inner Diopside triple points

% smooth the grains a bit
grains = smooth(grains,2);

% and plot them
plot(grains);

% on top plot the triple points
hold on
plot(tP('Diopside','Diopside','Diopside'),'displayName','Di-Di-Di','color','b')
hold off

Index triple points by grains

Since, triple points are asociated to grains we may single out triple points that belong to a specific grain or some subset of grains.

% find the index of the largest grain
[~,id] = max(grains.area);

% the triple points that belong to the largest grain
tP = grains(id).triplePoints;

% plot these triple points
plot(grains(id),'FaceColor',[0.2 0.8 0.8],'displayName','largest grains');
hold on
plot(grains.boundary)
plot(tP,'color','r')
hold off

Index triple points by grain boundary

Triple points are not only a property of grains but also of grain boundaries. Thus we may ask for all triple points that belong to Fosterite - Forsterite boundaries with misorientation angle larger then 60 degree

% all Fosterite - Forsterite boundary segments
gB_Fo = grains.boundary('Forsterite','Forsterite')

% Fo - Fo segments with misorientation angle larger 60 degree
gB_large = gB_Fo(gB_Fo.misorientation.angle>60*degree)

% plot the triple points
plot(grains)
hold on
plot(gB_large,'linewidth',2,'linecolor','w')
plot(gB_large.triplePoints,'color','m')
hold off
 
gB_Fo = grainBoundary  
 
 Segments   mineral 1   mineral 2
      255  Forsterite  Forsterite
 
gB_large = grainBoundary  
 
 Segments   mineral 1   mineral 2
       55  Forsterite  Forsterite

Boundary segments from triple points

On the other hand we may also ask for the boundary segments that build up a triple point. These are stored as the property boundaryId for each triple points.

% lets take Forsterite triple points
tP = grains.triplePoints('Fo','Fo','Fo');

% the boundary segments which form the triple points
gB = grains.boundary(tP.boundaryId);

% plot the triple point boundary segments
plot(grains)
hold on
plot(gB,'lineColor','w','linewidth',2)
hold off

Once we have extracted the boundary segments adjecent to a triple point we may also extract the corresponding misorientations. The following command gives a n x 3 list of misorientations where n is the number of triple points

mori = gB.misorientation
 
mori = misorientation  
  size: 15 x 3
  crystal symmetry : Forsterite (mmm)
  crystal symmetry : Forsterite (mmm)
  antipodal:         true
 

Hence, we can compute for each triple point the sum of misorientation angles by

sumMisAngle = sum(mori.angle,2);

and my visualize it by

plot(grains,'figSize','large')
hold on
plot(tP,sumMisAngle ./ degree,'markerEdgeColor','w')
hold off
mtexColorMap(blue2redColorMap)
CLim(gcm,[80,180])
mtexColorbar
e = 
  PropertyEvent with properties:

    AffectedObject: [1×1 ColorBar]
            Source: [1×1 matlab.graphics.internal.GraphicsMetaProperty]
         EventName: 'PostSet'