Metallografie

Metallography is the branch of materials science that studies the microstructure of metals and their alloys through the preparation and microscopic examination of cross sections. The goal is to reveal features such as grains, grain boundaries, phase distribution, inclusions, and defects which influence mechanical properties and performance.

Typical workflow includes selecting a sample, sectioning, mounting, grinding with progressively finer abrasives, polishing to a mirror finish, and etching with chemical reagents to selectively attack the matrix or phases. Common etchants include Nital for steels and reagents such as Picral or Marble's reagent for other alloys. Etching reveals the microstructure by creating contrast between different phases and grain boundaries.

Imaging is performed with optical microscopes in reflected light; advanced techniques include scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) for crystallographic information, as well as microhardness mapping. Quantitative analysis may involve measuring grain size, phase fractions, and defect densities using image analysis.

Applications include characterization of heat-treated structures (such as pearlite, bainite, and martensite in steels), evaluation of aluminum and titanium alloys, failure analysis, quality control, and materials research. Metallography supports process development, material certification, and forensic analysis of failed components, providing a link between processing, structure, and properties.

Standards for metallography guide preparation and analysis, such as ASTM E3 for specimen preparation and ASTM E112 for grain-size determination, help ensure consistency and repeatability across laboratories.