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What is a Microstructure?

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  • Written By: M. McGee
  • Edited By: Lauren Fritsky
  • Last Modified Date: 06 November 2016
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A microstructure is the way a material comes together on a very small scale. An object's microstructure is not visible by the naked eye, although the patterns present at the microscopic level may replicate at a larger level. This larger level is the macroscopic level; it will give an observer a basic impression of the material’s underlying design. The object’s microstructure determines the majority of its physical properties. There are four main categories that materials fall into based on their microstructure: ceramic, metallic, polymeric and composite.

A material’s physical structure will appear to change depending on how closely you look at it. When an object is held at arm’s length, it looks different than if it is a hand’s width away from a person’s face. The same is true when an object is observed under a microscope. In order to create a standard definition of microstructure, the power of the magnification used to look at it is no more than 25x.

When the structure is observed at a higher or lower power, it looks different. These other observable structures, particularly the smaller ones, can have a significant impact on the properties of the object. Instead of expanding the definition of microstructure, the elements that make up the microstructure are changed to accommodate differences in underlying structure.

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As an example, it is possible to look at the macroscopic world. If a highway system was the observed item, a road would be the microstructure. Different roads are made of different materials and, therefore, have different properties. Thus, the road is broken down into types of roads.

Generally, a microstructure is observed by taking paper-thin slices of the object and putting them under a microscope. These slices are so thin that light shines through them and highlights the underlying structure. Depending on the material observed, other methods may be employed such as electron microscopy or x-rays.

Through seeing the materials present and by observing the way they interact, it is possible to predict the way a material will act on a macroscopic level. Certain materials have certain properties, so when they are present, they pass those properties onto the material as a whole. Their underlying structure also shows how a material will act. For instance, a material where the structure is arranged in long non-interlocking plates may be prone to breaking or bending.

These properties come together to give the material a broad classification. These classes tell the basic properties of a material without the need to observe its actual structure. Three of them—ceramic, metallic and polymeric—are pure collections of a specific type of structure. The forth, composite, is a mixture of the three basic kinds.

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