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| A
polycrystalline material is comprised of many small crystallites with different
crystal orientations that are separated by grain boundaries. This is the
common structure of most technical materials.
The photograph shows the polycrystalline structure of a Pratt and Whitney turbine blade. The blade has been cast to a near net shape, and the surface has been etched to show the individual crystallites. In this blade, crystallite size is about 1 mm and the overall blade length about 75 mm. |
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