Crystal Orientation Mapping: Orientation Coloring SchemePatrick Camus, Ph.D., Thermo Fisher Scientific, Madison, WI, USA

Key Words

• Color Scheme

• EBSD

• Orientation Maps

Technical Note: 51923

Background

Electron backscatter diffraction (EBSD) orientation mappingprograms, like QuasOr, collect and measure the individualcrystal orientations with respect to the sample or detectoraxes. An easy way to describe these orientations isthrough the use of Euler angles. A set of Euler anglesconsists of 3 successive rotations about specific directionsto align the crystal axes with the reference axes. Colorcoding is used to illustrate these angular changes. In fact,2 orientation maps are required to fully describe thecrystal orientations with respect to the reference axes.

Description

The easiest way to illustrate the orientation of a crystal isthrough the use of an oriented unit cell “cube”. However,this graphical representation is best suited for showing theorientation of a single point, not for many points as in amap. The easiest way to map the Euler angles of a crystalorientation to the reference axes is to use colors mappedto a stereographic triangle. A usual convention is to place

red at the <100>, green at the <110>, and blue at the<111> directions. This coloring convention provides acolor crystal orientation map (COM) of the Euler angleswithin a sample.

However, a single map does not provide the completeanswer. A single map can actually have multiple crystalrotations for a single color representation. An examplecan be described as follows: a map with respect to thesample normal contains a grain which is colored red for a<100> orientation. This color can be assigned for a varietyof unit cell orientations. For instance, the unit cell “cube”could be oriented horizontally or rotated 45 and still begiven the color red.

For illustration purposes only (below), a COM can beannotated with unit cell “cubes.” Any regions which aresimilar in color have one similar orientation with respectto the reference axis, but the rotation about that axis israndom. This can be seen by examining all the “cubes”associated with the red grains in a “sample normal”reference direction. All these “cubes” should have a cube-face upward, but with a random rotation about this“out-of-paper” direction. This rotation shows that aconstant red color does NOT mean that the orientationsof all commonly colored grains are identical. Therefore,additional information is required to fully describe thecrystal orientations.

Color map for orientations within a stereographic triangle

Unit cell “cube” forspecific Euler angles ϕ1, Φ, ϕ2

Valid “cube” orientations for a red pixel in a “normal” COM

A second COM is usually displayed to illustrate thisadditional orientation information (see figure above). This COM has the same color scheme based on thestereographic triangle, but it is with respect to a differentreference axis. The reference axes include “transverse”(vertical), “reference” (horizontal), and “normal” (out-of-paper). Close examination of the colors in the two COM’sto determine the rotations about the specific axes canpredict the orientation of the “cube”.

Conclusion

A single COM is not sufficient to adequately describe theorientations measured by QuasOr. Thus, two COM’s withrespect to different reference axes fully describes theorientations within the sample.

Part of Thermo Fisher Scientific

TN51923_E 06/10M

Normal Reference Transverse

COM images of same data set colored using the stereographic triangle scheme with respect to the indicated reference axis. Note the variation of color for the same grain between the images necessitating multiple displays for correct interpretation of the orientation data.

In addition to these

offices, Thermo Fisher

Scientific maintains

a network of represen -

tative organizations

throughout the world.

Africa-Other+27 11 570 1840Australia+61 3 9757 4300Austria+43 1 333 50 34 0Belgium+32 53 73 42 41Canada+1 800 530 8447China+86 10 8419 3588Denmark+45 70 23 62 60 Europe-Other+43 1 333 50 34 0Finland / Norway /Sweden+46 8 556 468 00France+33 1 60 92 48 00Germany+49 6103 408 1014India+91 22 6742 9434Italy+39 02 950 591Japan +81 45 453 9100Latin America+1 561 688 8700Middle East+43 1 333 50 34 0Netherlands+31 76 579 55 55New Zealand+64 9 980 6700South Africa+27 11 570 1840Spain+34 914 845 965Switzerland+41 61 716 77 00UK+44 1442 233555USA+1 800 532 4752

Thermo Electron ScientificInstruments LLC, Madison, WIUSA is ISO Certified.

www.thermoscientific.com©2010 Thermo Fisher Scientific Inc. All rights reserved. All trademarks are the property of Thermo Fisher Scientific Inc. and its subsidiaries. Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your local sales representative for details.