Transcript Introduction to EBSD

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
Introduction to EBSD - History
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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
Introduction to EBSD - Hardware
• Schematic layout o
components
Introduction to EBSD - Collection
Geometry
• 70.5 deg tilt
• Approx. 70
steradian of
pattern
detected
• Distances
shown are
arbitrary
Introduction to EBSD - Forward
Scattered Electron Imaging (FSE)
• FSE greatly
enhances
diffraction
contrast in
imaging
• Grains and
grain
boundaries
are clearly
revealed
Introduction to EBSD - FSE Examples
• Nickel
• Austenitic
Stainless
Steel
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
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