Observation of microstructure of nodular graphite in ductile iron by atomic force microscopy

Atomic force microscopy (AFM) was applied to investigate the characteristic s of surface topography and the microstructure of nodular graphite (NG) in ductile iron. Surface topography was measured at different intersection pla nes in NG. Differences between the central profile and the surrounding prof ile were caused by the cleavage of graphite under radial orientation of NG. Lateral force images and in situ scratching measurements showed the existen ce of fine spheroidal platelets. Crystal orientation of nodular graphite wa s understood from the arrays of spheroidal platelets. Brachyaxes of spheroi dal platelets were oriented in the radial direction to form a fan-shaped st ructure in NG. Some platelets, however, showed anomalous orientations.