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;

% import the data
mtexdata forsterite silent

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

% and recompute grains
[grains,ebsd.grainId] = calcGrains(ebsd('indexed'),'minPixel',5);

% 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
      869  27592 µm  notIndexed  Forsterite
       36   1562 µm  notIndexed   Enstatite
       42   1361 µm  notIndexed    Diopside
     1398  56197 µm  Forsterite  Forsterite
      654  26372 µm  Forsterite   Enstatite
      522  20750 µm  Forsterite    Diopside
       35   1296 µm   Enstatite   Enstatite
      134   5802 µm   Enstatite    Diopside
       23    951 µm    Diopside    Diopside

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

hold on
plot(grains.boundary('Fo','Fo'),'lineColor','blue','micronbar','off','lineWidth',4)
hold off

Similarly, we may select all Forsterite to Enstatite boundary segments.

hold on
plot(grains.boundary('Fo','En'),'lineColor','darkgreen','micronbar','off','lineWidth',4)
hold off

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

grains.boundary('Fo','En').misorientation(1)
grains.boundary('En','Fo').misorientation(1)
ans = misorientation (Forsterite → Enstatite)
 
  Bunge Euler angles in degree
     phi1     Phi    phi2
  239.986 50.6875 124.673
 
 
ans = misorientation (Enstatite → Forsterite)
 
  Bunge Euler angles in degree
     phi1     Phi    phi2
  55.3267 50.6875 300.014

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 misorientations according to twist / tilt character or twinning is explained in linked sections.