Microstructure of Metals

the structure of a metal, revealed by an optical or electron microscope. The microscope was first used for studying metals by P. P. Anosov in 1831 in examining damask steel.

Metals and alloys consist of a large number of irregularly shaped crystals (grains), which are usually indiscernible to the naked eye. The grains are rounded or elongated; they may be large or small and are arranged in a regular order or randomly. The shape, size, arrangement, and orientation of the grains depend on the conditions of their formation.

The part of the microstructure that has a uniform structure is called the structural component (for example, excess crystals, eutectics, and eutectoids, particularly for the ferrocarbon alloys austenite, ferrite, cementite, pearlite, ledeburite, and martensite).

The quantitative ratio of the structural components of an alloy is determined by its chemical composition and the conditions under which it was heated and cooled. The microstructure is also characterized by the arrangement and number of certain lattice defects. Many mechanical and physical properties of materials depend on the microstructure.