Einschlusskörper

Einschlusskörper is a discrete particle embedded in a solid or liquid matrix that differs in composition or phase from the surrounding material. In materials science and engineering, inclusions are often impurities or secondary phases that become trapped during processing. They can be solid, liquid, or gaseous and may originate from processing steps such as melting, casting, or deoxidation, as well as from contamination or reaction products. In metals, common inclusions are non-metallic oxides, sulfides, silicates, carbides, and nitrides.

Characterization and detection: In practice, inclusions are identified and analyzed using metallographic preparation, optical microscopy, scanning electron microscopy with energy-dispersive spectroscopy, and non-destructive methods such as X-ray microtomography. Standards and classifications exist for assessing inclusion content and quality, particularly in steel.

Impact and control: The presence of inclusions can act as stress concentrators and crack initiation sites, reducing toughness, fatigue life, and corrosion resistance depending on size, shape, distribution, and interface with the matrix. In many industrial processes, inclusion control is important; methods include refining and deoxidation, filtration, slag control, and inclusion-modifying tactics that promote finer, more benign phases or favorable distribution.

Examples and other uses: In steel, oxides and sulfides such as alumina and manganese sulfide are typical inclusions; in cast aluminum alloys oxide films can occur; in cast iron graphite particles function as a primary inclusion phase. The term Einschlusskörper is also used in geology to describe foreign mineral grains trapped within a host mineral, and in biology to refer to intracellular inclusion bodies.