EBSD for beginners
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Microstructural analysis with EBSD
Microstructure is important because it determines many of the physical properties of materials. For example, grain size can influence tensile strength and the properties of grain boundaries can determine the way in which materials fracture. Optical microscopy and scanning electron microscopy are both used to examine microstructure. Polishing and chemical etching can reveal the positions of grains and grain boundaries. However, these techniques may not reveal all the grains. This is where EBSD comes in - it measures crystal orientation and so must be able to show unambiguously the position of all grains and grain boundaries.
EBSD is used to form crystal orientation maps by scanning the electron beam over the sample and measuring the orientation from the diffraction pattern at each point. In a crystal orientation map points with similar crystal orientations are shown in similar colours. In these maps a grain is a region of the sample where the crystal orientation is the same within a certain orientation angle tolerance. The maps can be processed to show with certainty the position of all the grains and grain boundaries.
EBSD is unique in that it provides a link between microstructure and crystallography. It complements conventional analysis techniques by providing definitive information about the crystal orientations present in the sample.
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Microstructure revealed on material surface by chemical etching. |
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Click to see the corresponding crystal orientation data from this sample |
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