Qualitative and quantitative structure analysis
By means of the structural analysis of polycrystalline materials, significant correlations between production, microstructure and the expected properties of a material are determined. Many property-relevant structural features such as grain size and grain form, segregations, errors and textures can only be detected by microscopic analysis. The microstructure of a material is characterized by the complete concatenation of order fields (crystalline or amorphous type) with intervening interfaces (phase and grain boundaries). Materialography as a discipline describes the investigation of the structural composition by optical means and methods and aims to describe the structure both qualitatively and quantitatively on the basis of various parameters and characterize them.
Goal/
Structural feature of interest
Characterization
- Type of structure (primary/secondary structure; castings/ deformation state)
Description based on characteristic features, such as preferred directions, dendritic structures, grain shape
- Definition of existing phases
Description of the present phases based on shape, size, arrangement, area percentage, color
- Precipitations (carbides, nitrides, silicides, intermetallic phases)
Description based on form and color, classification according to standards (eg Stahleisenpruefblatt 1520 -. Carbides in steels)
- Structural defects (pores, voids, cracks)
Characterization according to shape, size, proportion and distribution (e.g. VDG test sheet P202)
- Particle size/shape (influence of thermal and mechanical processes)
Characterization on direct measurements (e.g. DIN EN ISO 643, ASTM E112)
- Contaminations (non-metallic inclusions in steel, oxide inclusions in cast materials, foreign inclusions in ceramics)
Characterization based on shape and color according to different standards (e.g. EN ISO 10247, ASTM E45 -. Content of nonmetallic inclusions in steels)
- Homogeneity (density distribution in sintered materials, segregations)
Characterization via quantitative measurements or qualitatively on the microscopic image
- Textures (solidification or deformation textures)
Microstructure in castings depends on geometries or cooling conditions or textures by forming