Influence of martensite morphology and its dispersion on mechanical properties and fracture mechanisms of Fe-Mn-C dual phase steels

The influence of martensite morphology and its geometrical distribution in ferrite matrix on the mechanical properties and fracture mechanisms of Fe-Mn-C dual phase steels has been studied experimentally. Special attention has been paid to the determination of the fracture mechanisms. Examination of the repolished longitudinal sections of fractured specimens by scanning electron microscopy has revealed that, according to their different morphologies and dispersions, the main mechanism of void formation in these dual phase steels can change from martensite cracking to decohesion at the ferrite/martensite interface. These two features, in turn, can determine the failure mechanisms of the specimen: cleavage or ductile `cup and cone' fracture. In addition, the observed mechanical properties have been related to these modes of fracture.