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Prepare a laboratory specimen with care not to
remove inclusions, erode grain boundaries or compromise the sample in some other
way. Study structural characteristics in relation to its physical and mechanical
properties at low and high magnification. Take careful note of grain size,
shape, and distribution of secondary phases and nonmetallic inclusions.
Segregation and other heterogeneous conditions also influence the mechanical
properties and behavior characteristics of metal.
Metallography for the analyst may be concerned with pit depth, intergranular corrosion, hydrogen attack and embrittlement, caustic embrittlement, stress corrosion cracking (intergranular or transgranular), and corrosion, mechanical or thermal fatigue. Also, within limits, an almost complete history of the mechanical and thermal treatment received by a metal is reflected in its microstructure.
