Experimental data

To use the STABiX toolbox, some experimental data are required :

  • average grain orientations (Euler angles (\(\phi_{1}\), \(\Phi\), \(\phi_{2}\)) in degrees) or intragranular misorientation (misorientation axis \([uvw]\) / angle \(\omega\));
  • grains boundaries positions (optional for the bicrystal analysis);
  • grains positions (optional for the bicrystal analysis);
  • geometry of grain boundaries (trace angle and grain boundary inclination) (optional).

TEM experiments can provide intragranular misorientation and EBSD measurements can provide average grain orientations, grains boundaries and grains positions, and grain boundary trace angle.

Inclination of the grain boundary can be evaluated by serial polishing or focused ion beam (FIB) sectioning, either parallel or perpendicular to the surface of the sample.

EBSD map GUI

To plot EBSD map in the EBSD map GUI, two types of TSL-OIM files are required :

  • Reconstructed Boundaries File ;
  • Grain File Type 2.

TSL-OIM data preparation

Open you .osc (or your .ctf) file in the TSL-OIM Analysis Software.

Warning

Set the TSL coordinates system !

Change data properties for the detection of grain boundaries (All data –> Properties).

Clean up your dataset (Filename –> Cleanup).

Reference : OIM ANALYSIS 6.0 (user manual) and OIM ANALYSIS 7.0 (user manual) / EDAX website

Reconstructed Boundaries File

Export “Reconstructed Boundaries File” of the cleaned dataset (All data –> Export –> Reconstructed Boundaries), with the following options defined by default :

  • Right hand average orientation (\(\phi_{1}\), \(\Phi\), \(\phi_{2}\)) in degrees ;
  • Left hand average orientation (\(\phi_{1}\), \(\Phi\), \(\phi_{2}\)) in degrees ;
  • Trace angle (in degrees) ;
  • (\(x,y\)) coordinates of endpoints (in microns) ;
  • IDs of right hand and left hand grains.

Note

Reconstructed boundary methodology is only applied to data collected on a hexagonal grid. Nevertheless, it is possible to convert a square grid into an hexagonal grid in TSL-OIM software.

Warning

It is not possible to export a “Reconstructed Boundaries File”, containing “opened” grain boundaries.

Example of “Reconstructed Boundary File”: MPIE_cpTi_reconstructed_boundaries_2013.txt

The Matlab function used to read “Reconstructed Boundary File” is : read_oim_reconstructed_boundaries_file.m

If some GBs segments are missing or some wrong segments are exported, play with partition properties in the TSL-OIM software in order to export a more realistic Reconstructed Boundaries file:

  • decrease/increase “Grain Tolerance Angle” ;
  • decrease/increase “Minimum Grain Size” ;
  • decrease/increase the maximum deviation between reconstructed boundary and corresponding boundary segments.

Grain File Type 2

Export “Grain File Type 2” of the cleaned dataset (All data –> Export –> Grain File), with the following options :

  • Integer identifying grain ;
  • Average orientation (\(\phi_{1}\), \(\Phi\), \(\phi_{2}\)) in degrees ;
  • Average position (\(x,y\)) in microns ;
  • An integer identifying the phase ;
  • Edge or interior grain (optional) ;
  • Diameter of the grain in microns (optional).

Note

Export the “Grain File Type 2” in the same location as the corresponding “Reconstructed Boundary File”.

Example of “Grain Gile Type 2”: MPIE_cpTi_grain_file_type2_2013.txt

The Matlab function used to read “Grain File Type 2” is : read_oim_grain_file_type2.m

Loading other type of EBSD data files…

It is possible to load other type of EBSD data files (e.g. : .ctf files), using the ‘import_wizard’ of the MTEX toolbox.

First, download and install the MTEX Toolbox.

Then, import your EBSD data (e.g.: .ang file) and set the coordinate systme, using the ‘import_wizard’ and save the EBSD dataset in the Matlab workspace as a variable named ‘ebsd’, and press ‘Finish’.

The EBSD map is automatically plotted from the imported data. The coordinate system and the scan unit are set from the properties of the imported data.

Note

For a single phase material, the phase number is 0 or 1. For a two phases material, the phase numbers are respectively 1 and 2. For non-indexed pixels, the phase is numbered as -1.

How to generate a .ang file with TSL-OIM software ?

Export “Scan Data (.ang file)” of the cleaned dataset (Filename –> Export –> Scan Data) (optional).

Example of an .ang file.

The Matlab functions used to generate .ang file v6 and v7 are respectively:

Possible errors introduced during files exportation from TSL-OIM

  • “Grain File Type 2” –> Missing integer identifying grain
    • Solved when file is imported via the GUI.
  • “Reconstructed Boundary File” –> Inversion of left and right grains for a given grain boundary
    • Cross product performed between GB vector and center of grains to check (if cross product < 0 : no inversion, and if cross product > 0 : inversion).
  • “Reconstructed Boundary File” –> \(x\)-axis and \(y\)-axis not corrects…
    • \(y\) coordinates is multiplied by -1 when file is imported via the GUI.

Note

All of these issues are taken into account and corrected automatically when user is loading his data via the EBSD map GUI.

Issues with plot of EBSD maps

Sometimes, grain boundaries coordinates are too big compared to the grain size, because of the Voronoi tesselation for example. Thus, the following plot can be obtained :

_images/error_axis_limits.png

Figure 12 Screenshot of the EBSD map GUI with a problem of axis limits.

In this case, it is advised to use the ‘zoom’ function of Matlab to zoom in and zoom out in the center of the EBSD map, to vizualize the grains. It is also possible to set directly the limits of axis (e.g.: xlim([0 1500]); ylim([-1000 0]);) in the command window of Matlab.

Bicrystal GUI

The YAML configuration file provides a simple way to define a bicrystal.

An example of bicrystal configuration file is given here : config_gui_BX_defaults.yaml

Copy this example file and modify it with your data. Be careful to put a space after the comma in a list (e.g. [\(x\), \(y\), \(z\)]).

Warning

Don’t change fieldnames and don’t round Euler angles. Euler angles are given in degrees.

Load your YAML bicrystal configuration file via the menu in the bicrystal GUI. You may have to run again the path_management.m Matlab function, if your YAML bicrystal configuration file is not found by Matlab.

Visit the YAML website for more informations.

Visit the YAML code for Matlab.

Convention for bicrystal EBSD/indentation experiments

_images/Bicrystal_conventions.png

Figure 13 Geometrical convention of a bicrystal.