Grain Boundary Tutorial edit page

A quick guide to grain boundary analysis

Grain boundaries generation

To work with grain boundaries we need some ebsd data and have to detect grains within the data set.

% load some example data
mtexdata twins

% detect grains
[grains,ebsd.grainId,ebsd.mis2mean] = calcGrains(ebsd('indexed'))

% smooth them
grains = grains.smooth

% visualize the grains
plot(grains,grains.meanOrientation)
ebsd = EBSD (y↑→x)
 
 Phase  Orientations     Mineral         Color  Symmetry  Crystal reference frame
     0     46 (0.2%)  notIndexed                                                 
     1  22833 (100%)   Magnesium  LightSkyBlue     6/mmm       X||a*, Y||b, Z||c*
 
 Properties: bands, bc, bs, error, mad
 Scan unit : um
 X x Y x Z : [0, 50] x [0, 41] x [0, 0]
 Normal vector: (0,0,1)
 
 
grains = grain2d (y↑→x)
 
 Phase  Grains  Pixels    Mineral  Symmetry  Crystal reference frame
     1     121   22833  Magnesium     6/mmm       X||a*, Y||b, Z||c*
 
 boundary segments: 4416 (1154 µm)
 inner boundary segments: 4 (1.2 µm)
 triple points: 114
 
 Properties: meanRotation, GOS
 
 
ebsd = EBSD (y↑→x)
 
 Phase  Orientations     Mineral         Color  Symmetry  Crystal reference frame
     0     46 (0.2%)  notIndexed                                                 
     1  22833 (100%)   Magnesium  LightSkyBlue     6/mmm       X||a*, Y||b, Z||c*
 
 Properties: bands, bc, bs, error, mad, grainId, mis2mean
 Scan unit : um
 X x Y x Z : [0, 50] x [0, 41] x [0, 0]
 Normal vector: (0,0,1)
 
 
ebsd = EBSD (y↑→x)
 
 Phase  Orientations     Mineral         Color  Symmetry  Crystal reference frame
     0     46 (0.2%)  notIndexed                                                 
     1  22833 (100%)   Magnesium  LightSkyBlue     6/mmm       X||a*, Y||b, Z||c*
 
 Properties: bands, bc, bs, error, mad, grainId, mis2mean
 Scan unit : um
 X x Y x Z : [0, 50] x [0, 41] x [0, 0]
 Normal vector: (0,0,1)
 
 
grains = grain2d (y↑→x)
 
 Phase  Grains  Pixels    Mineral  Symmetry  Crystal reference frame
     1     121   22833  Magnesium     6/mmm       X||a*, Y||b, Z||c*
 
 boundary segments: 4416 (1022 µm)
 inner boundary segments: 4 (0.99 µm)
 triple points: 114
 
 Properties: meanRotation, GOS

Now we can extract from the grains its boundary and save it to a separate variable

gB = grains.boundary
gB = grainBoundary
 
 Segments  length   mineral 1  mineral 2
     1197  184 µm  notIndexed  Magnesium
     3219  837 µm   Magnesium  Magnesium

The output tells us that we have 3219 Magnesium to Magnesium boundary segments and 606 boundary segments where the grains are cut by the scanning boundary. To restrict the grain boundaries to a specific phase transition you shall do

gB_MgMg = gB('Magnesium','Magnesium')
gB_MgMg = grainBoundary
 
 Segments  length  mineral 1  mineral 2
     3219  837 µm  Magnesium  Magnesium

Properties of grain boundaries

A variable of type grain boundary contains the following properties

  • misorientation
  • direction
  • segLength

These can be used to colorize the grain boundaries. By the following command we plot the grain boundaries colorized by the misorientation angle

plot(gB_MgMg,gB_MgMg.misorientation.angle./degree,'linewidth',2)
mtexColorbar