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;

% import the data
plottingConvention.default('y↑→x');
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] = calcGrains(ebsd,'minPixel',5,'alpha',10);

% smooth the grains a bit
grains = smoothBoundary(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 (y↑→x)
 
 Segments    length   mineral 1   mineral 2
      555  27532 µm  notIndexed  Forsterite
       32   1586 µm  notIndexed   Enstatite
       29   1386 µm  notIndexed    Diopside
     1178  54925 µm  Forsterite  Forsterite
      554  26047 µm  Forsterite   Enstatite
      440  20260 µm  Forsterite    Diopside
       27   1278 µm   Enstatite   Enstatite
      123   5723 µm   Enstatite    Diopside
       22    930 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
  239.134 51.5067 125.138
 
 
ans = misorientation (Enstatite → Forsterite)
 
  Bunge Euler angles in degree
     phi1     Phi    phi2
  104.132 101.992  163.38

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.