PPT Slide
The term polycrystalline refers to any material which is composed of many individual grains.
However, some materials are actually used in their single crystal state: silicon for integrated circuits and nickel alloys for aircraft engine turbine blades are two examples.
The sizes of individual grains vary from submicrometer (for nanocrystalline structures) to millimeters and even centimeters (for materials especially processed for high-temperature creep resistance).
Figure 16.7 shows typical equiaxed grain configurations for polycrystalline tantalum and titanium carbide.