Fractographically determined microstructural parameters of sintered metallic materials

The new fractographical concept of porosity and particle connection classif ication in sintered metallic materials is presented in the paper. The plain porosity and particle connection porosity (bridge porosity) are defined an d described. Dimension and morphology of particle connections are very impo rtant microstructural parameters. Pores in a loaded sintered, body in relat ion to their character act in two contradictory ways. Besides the micronotc h 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 f acets in sintered iron, failed at the temperature -196 degreesC, depends on the porosity level.