Select Grain Boundaries

Select Grain Boundaries edit page

In this section we explain how to extract specific grain boundaries. Therefore we start by importing some EBSD data and reconstructing the grain structure.

close all; plotx2east

% import the data
mtexdata forsterite silent

% restrict it to a subregion of interest.
ebsd = ebsd(inpolygon(ebsd,[5 2 10 5]*10^3));

[grains,ebsd.grainId] = calcGrains(ebsd('indexed'));

% remove very small grains
ebsd(grains(grains.grainSize <= 5)) = [];

% and recompute grains
[grains,ebsd.grainId] = calcGrains(ebsd('indexed'));

% smooth the grains a bit
grains = smooth(grains,4);

% visualize as a phase map
plot(ebsd)
hold on
plot(grains.boundary,'linewidth',2)
hold off

The output of

grains.boundary

ans = grainBoundary
 
 Segments    length   mineral 1   mineral 2
      439  27383 µm  notIndexed  Forsterite
       18   1550 µm  notIndexed   Enstatite
       22   1350 µm  notIndexed    Diopside
     1386  55739 µm  Forsterite  Forsterite
      656  26512 µm  Forsterite   Enstatite
      519  20576 µm  Forsterite    Diopside
       35   1296 µm   Enstatite   Enstatite
      112   4827 µm   Enstatite    Diopside
       28   1250 µm    Diopside    Diopside

tells us the number of boundary segments between the different phsaes. Those segments with notIndexed phase include also those boundary segments where the grains are cutted by the scanning boundary. To restrict the grain boundaries to a specific phase transistion you shall do

hold on
plot(grains.boundary('Fo','Fo'),'lineColor','blue','micronbar','off','lineWidth',2)
hold off

Similarly we may select all Forsterite to enstatite boundary segements.

hold on
plot(grains.boundary('Fo','En'),'lineColor','darkgreen','micronbar','off','lineWidth',2)
hold off

Note, that the order of the phase names matter when considering the corresponding misorintations

grains.boundary('Fo','En').misorientation(1)
grains.boundary('En','Fo').misorientation(1)

ans = misorientation (Forsterite → Enstatite)
 
  Bunge Euler angles in degree
    phi1     Phi    phi2
  24.399 50.2291 261.351
 
 
ans = misorientation (Enstatite → Forsterite)
 
  Bunge Euler angles in degree
     phi1     Phi    phi2
  278.649 50.2291 155.601

In the fist case the misorientation returned is from Forsterite to Enstatite and in the second case its exactly the inverse

The selection of grain boundaries according to specific misorientationsm according to twist / tild character or twinning is explained in linked sections.