A material’s internal structure or microstructure is defined as one that is viewed with either a metallurgical microscope at magnifications in the range of 25X up to 1000X or a scanning electron microscope (SEM) at higher magnifications. Features observed in microstructures include phases and precipitates in processed materials, dendritic structures in cast alloys, heat-affected zones in welds, layer thicknesses in coated materials, and corrosion modes and depths in affected parts.

Microstructural examination yields valuable information on the mechanical and thermal treatments performed on the material and is important in characterizing materials for quality purposes. We can say that the microstructure of a material acts as a record of its process history.  Because many material properties such as tensile strength and ductility are influenced by process history, microstructures can be used to estimate such properties. As such, microstructural analysis is an important screening tool in the research and development of new materials. Failure analysis investigations rely on microstructures to determine failure origins and property changes in the material while in service.

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