2D-3D CONVERSION OF OBJECT SIZE DISTRIBUTIONS IN QUANTITATIVE METALLOGRAPHY

In common metallographic laboratory practice, object distributions in discontinuous multi-phase microstructures are characterized by incident light optical or scanning electron microscopy micrographs of polished planar microsections. Precipitation or dispersion particle hardened metal alloys and steel inclusions (e.g. MnS) constitute prominent examples but also sintering, welding or creep pores in metallic or ceramic materials are amongst related structures. The area and from it the volume fraction of these objects can be taken directly from such micrograph series, simplest by applying digital image analysis. However, the conversion of deduced two-dimensional into true three-dimensional particle (or pore) size distributions, which represents an important task of quantitative metallography e.g. for the computation of model distributions of limited extent as representative volume elements or establishing reasonable steel cleanliness specifications in the framework of material quality assurance, requires a mathematical calculation. In the present work, therefore, a simplified correction tech-nique that offers an often-appropriate method for the necessary stereological analysis is derived and exemplarily applied to a known model and a real dispersion microstruc-ture. The usability of this 2D-3D objects size conversion procedure and its restrictions are also discussed