Influence of aluminium on silicon microsegregation in solution strengthened ductile iron

Abstract

The excellent static mechanical properties of solid solution strengthened grades of ferritic ductile iron (SSFDI) are adjusted by elevated silicon contents and undergo a rapid loss above a critical content of about 4.3 wt-% silicon. This phenomenon is attributed to the formation of iron-silicon superstructures that is intensified in particular by the formation of silicon microsegregation. In order to affect silicon microsegregation, the alloying concept of SSFDI has been modified. In the present investigations, an inversion of the silicon microsegregation profile could be achieved by alloying a nodular cast iron melt with 1.2 wt-% aluminium. The results provide a metallurgical tool to shift the silicon embrittlement to higher silicon contents and thus to further enhance the mechanical properties of SSFDI.