A new understanding on the relation among microstructure micro interfacial mechanical behaviours and macro mechanical properties in cast iron

By using an SEM, micro-specimens of grey and nodular iron with ferrite matrix were serially intermittently loaded, observed in situ and photographed. Their micro deformation and fracture processes, especially interfacial mechanical behaviours, were investigated. Graphite internal fracture or graphite/matrix interfacial cracking processes carried out until final fracturing was found out. It has been confirmed that graphites in cast iron could not always be regarded as voids with almost no strength and a new explanation on graphite related to mechanical properties has been made. On the basis of the new understanding, an optimum microstructure was designed and its excellent mechanical properties were proved.