Abstract
The new fractographical concept of porosity and particle connection classification in sintered metallic materials is presented in the paper. The plain porosity and particle connection porosity (bridge porosity) are defined and described. Dimension and morphology of particle connections are very important microstructural parameters. Pores in a loaded sintered body in relation to their character act in two contradictory ways. Besides the micronotch effect, the slip steps may be formed on the surface of pores. This effect has been named "negative dislocation pile up". The porosity is responsible for the microinhomogeneity of plastic deformation and disappearance of the transition character of sintered iron toughness. The portion of cleavage facets in sintered iron, failed at the temperature -196 °C, depends on the porosity level.

Key words
new microstructural parameters, particle connection, plain porosity, particle connection porosity, form factor of porosity, bridge inclusions, deformation inhomogeneity, negative pile up

Full text not available