Relationship between mechanical properties and structure in austempered alloyed compacted graphite cast iron

Abstract

Austempering kinetic measurements and mechanical property measurements are presented for a compacted graphite iron of composition Fe-3.4C-3.5Si-0.25Mn-0.50Mo-0.50Ni (wt-%) austempered at 375°C after austenitising at 890 and 940°C. Analysis of the austempering kinetics shows that alloying elements have a similar effect on the processing window as in ductile irons. The mechanical properties show optimum values at austempering times within the processing window. However, the graphite morphology limits the mechanical property enhancement achieved by austempering. Nevertheless, it is possible to double the strength of the as cast compacted graphite iron without loss in ductility.