Boundary Plots edit page

Here we describe how to visualize grain boundary properties, e.g., misorientation angle, misorientation axes. Therefore lets 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));

% reconstruct grains
[grains,ebsd] = calcGrains(ebsd,'minPixel',5,'alpha',10);

% smooth the grains a bit - ebsdId is read per segment further down, so keep
% every segment between the pair of pixels it was measured from
grains = smoothBoundary(grains,4,'noSimplify','noRefine')
grains = grain2d (y↑→x)
 
 Phase  Grains  Pixels     Mineral  Symmetry         Color
     1      52   14016  Forsterite       mmm  LightSkyBlue
     2      13    1375   Enstatite       mmm  DarkSeaGreen
     3      21     693    Diopside     12/m1     Goldenrod
 
 boundary segments: 3288 (141261 µm)
 inner boundary segments: 12 (464 µm)
 triple points: 122
 
 Properties: meanRotation, GOS

The grain boundary segments of a list of grains are stored within the field

gB = grains.boundary
gB = grainBoundary (y↑→x)
 
 Segments    length   mineral 1   mineral 2
      489  27814 µm  notIndexed  Forsterite
       25   1615 µm  notIndexed   Enstatite
       24   1396 µm  notIndexed    Diopside
     1385  55477 µm  Forsterite  Forsterite
      653  26296 µm  Forsterite   Enstatite
      520  20622 µm  Forsterite    Diopside
       35   1296 µm   Enstatite   Enstatite
      134   5794 µm   Enstatite    Diopside
       23    951 µm    Diopside    Diopside

We may use the plot command to visualize the grain boundaries in the map

% plot phases and grain boundaries
plot(ebsd)
hold on
plot(gB,'lineWidth',2)
hold off

Specific boundaries

Accordingly, we can access the grain boundary of a specific grain by

grains(47).boundary

% lets highlight this specific grain by its boundary
hold on
plot(grains(47).boundary,'lineWidth',4,'lineColor','DarkBlue')
hold off
ans = grainBoundary (y↑→x)
 
 Segments   length   mineral 1  mineral 2
       29  1084 µm  Forsterite   Diopside
        4   305 µm   Enstatite   Diopside

For a multi-phase system, the location of specific phase transitions may be of interest. The following plot highlights all Forsterite to Enstatite phase transitions

hold on
plot(grains.boundary('Fo','En'),'linecolor','DarkGreen','linewidth',4)
hold off

Another type of boundaries is boundaries between measurements that belong to the same grain. This happens if a grain has a texture gradient that loops around these two measurements.

hold on
plot(grains.innerBoundary,'linecolor','red','linewidth',4)
hold off

Misorientation angle

The boundary misorientation is the misorientation between the two neighboring pixels of a boundary segment. Depending of the misorientation angle one distinguishes between high angle and low angle grain boundaries. In MTEX we can visualize the boundary misorientation angle by the commands

close all
gB_Fo = grains.boundary('Fo','Fo');
plot(grains,'translucent',1,'micronbar','off')
legend off
hold on
plot(gB_Fo,gB_Fo.misorientation.angle./degree,'linewidth',4)
hold off
mtexColorbar('title','misorientation angle')

The misorientation axes in crystal coordinates

Similarly as the rotational angle we may colorize the grain boundaries also according the misorientation axes. First of all we have to decide whether we want to visualize the rotational axis in crystal or coordinate system. Second we have to define a color key that translates rotational axes into colors.

Lets start with the rotational axes in crystal coordinates

% computed the axes in specimen coordinates
axes = gB_Fo.misorientation.axis

% define a color key
colorKey = HSVDirectionKey(axes);

% compute colors
color = colorKey.direction2color(axes);

hold on
plot(gB_Fo,'lineColor','black','linewidth',6) % some black background for contrast
plot(gB_Fo,color,'linewidth',4)
hold off
mtexColorbar('visible','off')
axes = Miller (Forsterite)
 size: 1385 x 1

As a colorbar replacement we plot the color key and on top of it the misorientation axes at the grain boundaries

figure(2)
plot(colorKey)
hold on
plot(axes,'MarkerFaceAlpha',0.1,'MarkerEdgeAlpha',0.3,'MarkerColor','black')
hold off

The misorientation axes in specimen coordinates

Analyzing the misorientation axis in specimen coordinates is a bit more involved as it requires to extract the two neighboring orientations to each boundary segment. To do this we use the ebsdId stored in the boundary segments.

figure(1)

% first we reduce the number of boundary segments a bit
% in order to avoid that the plot becomes to messy
gB_red = reduce(gB_Fo,5)

% next we extract for every boundary segment the two orientations at both
% sides
ori = ebsd('id',gB_red.ebsdId).orientations

% the two orientations we use to compute the misorientation axis in
% specimen coordinates
axes = axis(ori(:,1),ori(:,2))

% plot the projection of the misorientation axis on the measurement surface
hold on
quiver(gB_red,axes,'autoScaleFactor',0.4,'color','black')
hold off
gB_red = grainBoundary (y↑→x)
 
 Segments    length   mineral 1   mineral 2
      338  53654 µm  Forsterite  Forsterite
 
ori = orientation (Forsterite → y↑→x)
  size: 338 x 2
 
axes = vector3d (y↑→x)
 size: 338 x 1

Full Misorientation Colorization

In order to visualize the full misorientation, i.e., axis and angle, one has to define a corresponding color key. One option is the color key described in the paper by S. Patala, J. K. Mason, and C. A. Schuh, Improved representations of misorientation information for grain boundary, Prog. Mater. Sci., vol. 57, no. 8, pp. 1383-1425, 2012.

% plot the grains
close all
plot(grains,'micronbar','off')
legend off

% define the color key
colorKey = PatalaColorKey(gB_Fo);

hold on
plot(gB_Fo,'linewidth',7)
hold on
color = colorKey.orientation2color(gB_Fo.misorientation);
plot(gB_Fo,squeeze(color),'linewidth',4)
hold off

Lets visualize the color key as axis angle sections through the misorientation space

figure(2)
plot(colorKey,'layout',[3,4])

% and plot the misorientations on top
plot(gB_Fo.misorientation,...
  'MarkerFacecolor','none','add2all','MarkerSize',4)

Lets illustrate this color coding also at a iron sample.

% import the data
plottingConvention.default("y↓→x");
mtexdata csl

% grain segmentation and smoothing
[grains,ebsd] = calcGrains(ebsd);
grains = smoothBoundary(grains,2);
gB = grains.boundary('iron','iron');

% and plot image quality + orientation
close all
plot(ebsd,log(ebsd.prop.iq),'figSize','large')
mtexColorMap black2white
setColorRange([.5,5])
hold on
plot(grains,grains.meanOrientation,'FaceAlpha',0.4)

% define the color key and colorize the grain boundaries
colorKey = PatalaColorKey(gB)
color = colorKey.orientation2color(gB.misorientation);
hold on
plot(gB,squeeze(color),'linewidth',4,'smooth')
hold off
ebsd = EBSD (y↓→x)
 
 Phase   Orientations     Mineral         Color  Symmetry  Crystal reference frame
     0    5 (0.0032%)  notIndexed          none                                   
    -1  154107 (100%)        iron  LightSkyBlue      m-3m                         
 
 Properties: ci, error, iq
 Scan unit : um
 X x Y x Z : [0 → 511] x [0 → 300] x [0 → 0]
 Normal vector: (0,0,1)
 
 
colorKey = PatalaColorKey (iron → iron)
 
  antipodal: true

At the end we plot the colorized misorientation space in axis angle sections. Note that in this plot misorientations mori and inv(mori) are associated.

plot(colorKey,'axisAngle',(5:5:60)*degree,'layout',[3,4])

plot(gB.misorientation,'points',300,'add2all',...
  'MarkerFaceColor','none','MarkerEdgeColor','w')
plotting 300 random orientations out of 17569 given orientations

Citing this page. This page is part of the documentation of MTEX, a free and open source MATLAB toolbox for analyzing and modeling crystallographic textures. It was written by The MTEX Developers and is published at https://mtex-toolbox.github.io/BoundaryPlots.html. If you use MTEX, or reuse text or figures from this page, in your research, please cite

F. Bachmann, R. Hielscher, H. Schaeben: Texture Analysis with MTEX - Free and Open Source Software Toolbox, Solid State Phenomena 160 (2010), 63-68. 10.4028/www.scientific.net/SSP.160.63

BibTeX 
@article{bachmann2010mtex,
  author  = {F. Bachmann and R. Hielscher and H. Schaeben},
  title   = {Texture Analysis with MTEX - Free and Open Source Software Toolbox},
  journal = {Solid State Phenomena},
  volume  = {160},
  pages   = {63-68},
  year    = {2010},
  doi     = {10.4028/www.scientific.net/SSP.160.63},
  url     = {https://doi.org/10.4028/www.scientific.net/SSP.160.63}
}

Other papers describing specific MTEX methods are listed under Publications — please cite the one that best fits your application. The MTEX source code is licensed under the GNU General Public License v2.0; the text and figures of this documentation are licensed under CC BY 4.0, which permits reuse — including by automated systems — provided The MTEX Developers and this page are credited.