Structure of graphite precipitates in cast iron

Abstract

This study presents microstructural investigations of graphite precipitates found in cast irons. Binary Fe eC, FeeCeSb and FeeCeCe alloys containing different graphite morphologies (flake and spheroidal) were produced and compared to commercial irons in an attempt to rationalize the effect of Sb and Ce on graphite growth. The extensive use of transmission electron microscopy (mainly electron diffraction and high resolution lattice fringe imaging) enabled further understanding of graphite growth mechanisms. It was found that the inner structure of graphite precipitates consists of growth blocks stacked upon each other, for all investigated morphologies. This suggests that graphite crystals develop mainly by a 2D nucleation and growth mechanism, and that the final shape of the precipitates is associated to the occurrence of crystallographic defects in the graphite lattice (such as twins, misorientations and rotations) during growth.