MTEX Scripts

MTEX has no graphical user interface. You work with MTEX by writing MATLAB scripts: text files that keep the commands for an analysis in a reproducible order.

A typical script follows five steps.

During these steps, MATLAB stores data under names called variables. Each variable has a type, called its class, which determines the operations that can be applied to it. MTEX provides classes for objects such as vectors, rotations, EBSD data, grains, and orientation distribution functions (ODFs). The Function Reference lists all MTEX classes and functions.

Import and inspect data

Import functions create variables automatically. Here, fileName stores the path to an example CTF file. The second command imports that file and stores the result in the variable ebsd.

fileName = [mtexEBSDPath filesep 'Forsterite.ctf'];
ebsd = EBSD.load(fileName,'EulerCorrection', ...
  rotation.byAxisAngle(xvector,180*degree))

ebsd = EBSDsquare (y↓→x, row↓→col)
 
 Phase  Orientations     Mineral         Color  Symmetry  Crystal reference frame
     0   58485 (24%)  notIndexed          none                                   
     1  152345 (62%)  Forsterite  LightSkyBlue       mmm                         
     2   26058 (11%)   Enstatite  DarkSeaGreen       mmm                         
     3   9064 (3.7%)    Diopside     Goldenrod     12/m1        X||a*, Y||b, Z||c
 
 Properties: bands, bc, bs, error, mad, oldId
 Scan unit : um
 X × Y × Z : [0 → 36550] × [0 → 16750] × [0 → 0]
 Normal vector: (0,0,1)
 Square grid  :336 × 732

Leaving off the semicolon displays a summary of ebsd in the Command Window. This is a quick inspection step: the summary reports the phases, numbers of orientations, properties, map extent, and grid size. The 'EulerCorrection' option also corrects the imported orientations by the specified rotation.

Plot the phase map

Pass a variable to an MTEX function to operate on its data. The command below passes ebsd to plot and colors every indexed measurement by its phase.

plot(ebsd)

Notice the large blue forsterite regions, the smaller green enstatite and yellow diopside regions, and the white notIndexed areas. A notIndexed measurement is one whose diffraction pattern could not be indexed.

Reconstruct and inspect grains

The next command segments the measurements into grains. A grain is a phase-homogeneous, spatially connected region of EBSD measurements produced by segmentation. The 'minPixel' option excludes indexed grains with fewer than three measurements.

grains = calcGrains(ebsd,'minPixel',3)

grains = grain2d (y↓→x)
 
 Phase  Grains  Pixels     Mineral  Symmetry         Color
     0       8     811  notIndexed                    none
     1     490  151675  Forsterite       mmm  LightSkyBlue
     2     223   25747   Enstatite       mmm  DarkSeaGreen
     3     229    7674    Diopside     12/m1     Goldenrod
 
 boundary segments: 35830 (1.7e+06 µm)
 inner boundary segments: 285 (13165 µm)
 triple points: 1567
 
 Properties: meanRotation, GOS

The returned grain2d object is stored in grains. Its Command Window summary reports the number of grains in each phase and information about their boundaries.

Add the grain boundaries

Plotting on the same axes connects the result of the analysis to the phase map. hold on preserves the existing map while the boundary is added, and hold off ends that plotting state.

hold on
plot(grains.boundary,'lineWidth',2)
hold off

Notice that the dark lines trace changes between neighboring grains. Some lines lie within one color because grains of the same phase can still have different orientations.

Organize a script

An MTEX script is a sequence of MATLAB and MTEX commands. Add comments on lines beginning with % to record why each command is present. These explanations make the analysis understandable when the script is reopened.

Divide a longer script into sections with lines beginning with %%. In the MATLAB Editor, Ctrl+Enter runs the current section, while Ctrl+Shift+Enter runs it and advances to the next section. Running one section at a time lets you inspect each intermediate variable before continuing.

References

Next

Continue with Lists and Indexing to select parts of an MTEX variable and apply one operation to many stored objects.