Modeling of Ferrite Growth in Compacted Graphite Iron

• In the present work the ferrite growth in Compacted Graphite Iron (CGI) has been modeled. The relative amounts of ferrite and pearlite are of vital importance for the mechanical properties of cast iron. Thus, the possibility to predict the matrix microstructure in CGI by means of simulation would be an indispensable tool for foundries and design engineers. The increasing use of CGI, especially for automotive applications, further creates a need for this research.   This study shows that graphite in CGI grows in cells similar to eutectic grey iron cells. In cast irons the ferrite nucleates on the graphite and thereafter grows around the graphite particles until the formation of pearlite interrupts further ferrite formation. The complexity of the graphite particles in CGI imply that the ferrite will grow in different stages. A microstructure study of CGI reveals that ferrite nucleates on compacted graphite particles where low amounts of pearlite stabilizing elements can be found. Growth of ferrite then proceeds until it impinges with ferrite nucleated on adjacent graphite particles. Further ferrite growth takes place radially away from the center of the CGI cell until pearlite nucleation interrupts its growth. At some point during this process ferrite nucleates on graphite nodules in the last to freeze areas of the microstructure giving a contribution to the ferrite content. In the present work growth models of ferrite in nodular cast iron are adapted to CGI.

Nyckelord

Cast Iron

CGI

Ferrite Growth

Modeling

Eutectoid Transformation

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