MODULE 4 - Introduction to EBSD

1. MODULE 4 - Introduction to EBSD EBSD = Electron Backscatter Diffraction EBSD is a technique that allows: • Crystallographic Orientations • Misorientations • Texture trends • Grain size and boundary types • Phases To be characterised and quantified on a sub-micron scale

2. Introduction to EBSD - History • 1928 Kikuchi lines observed in TEM • 1954 Alam: patterns obtained in TEM • 1973 Venebles: patterns recorded on film in SEM • 1980 Patterns imaged with low light TV cameras • 1990 Automatic pattern solving using Hough transform • Present day • Local orientation and misorientation measurements • Crystal Orientation Mapping (COM) • Special grain boundaries imaged • Special textures revealed • Grain sizing

3. Introduction to EBSD - Hardware • Schematic layout of components

4. Introduction to EBSD - Collection Geometry • 70.5 deg tilt • Approx. 70 steradian of pattern detected • Distances shown are arbitrary

5. Introduction to EBSD - Forward Scattered Electron Imaging (FSE) • FSE greatly enhances diffraction contrast in imaging • Grains and grain boundaries are clearly revealed

6. Introduction to EBSD - FSE Examples • Nickel • Austenitic Stainless Steel

7. Introduction to EBSD - Crystal Orientation Mapping (COM) • Crystal uses reference electron image • Orientation obtained at every pixel • Color derived from inverse Pole Figure color key • Hough transform for every pixel stored for post acquistion reprocessing

8. Introduction to EBSD - Color Key for COMs • COM with Inverse Pole Figure color key for cubic material • Red = 100 • Green = 110 • Blue = 111 planes parallel to the surface