Ferrite Growth During Cooling Through the Ferrite-Austenite-Graphite Field in SGI

Abstract

This investigation examines the growth of ferrite during the cooling of spheroidal graphite cast irons through the ferrite-austenite-graphite phase field as conditioned by the partitioning of Silicon. Two different melts are examined. Ferrite growth was assumed to take place under paraequilibrium conditions. The study involves the measurement of the temperature of ferrite precipitation start under slow cooling conditions by DSC. Thermo-Calc was used to calculate the equilibrium concentration of Si at the ferrite precipitation start temperature. Calculated Si concentrations are compared to microsegregation profiles measured on the same alloys in a previous study. The results led to conclude that partitioning of Silicon does not represent a constraint for ferrite to grow between the upper and lower limits of the three-phase field, contradicting some of the existing literature.