Investigation on properties and microstructures of spheroidal graphite Fe–C–2Si and Fe–C–2Al cast irons

In this study, two types of spheroidal graphite cast irons were cast in a resin-bonded mould prepared by using a 1 m long fluidity pattern having different section thicknesses. The lengths of cast specimens were measured to determine the fluidity lengths and were X-rayed to see the porosity/void in the cast specimens. Density of each casting along the length was also determined. The experimental results show that the fluidity length of Fe–C–2Si cast iron is higher than that of Fe–C–2Al cast iron irrespective of section thickness. At the same time, as the section thickness increases, the density decreases indicating that the shrinkage porosity increases for both systems. It is also found that the amount of shrinkage porosity is more for the Fe–C–2Al cast iron than that of the Fe–C–2Si cast iron. As the section thickness increases, the presence of carbide in the microstructure decreases and that of the pearlite increases for both cast irons. However, the degree of nodularity for the graphite and the ferrite rings are better in the matrix structure of the SG–Si cast iron compared to those for the SG–Al cast iron. The overall results show that the solidification characteristics of the Fe–C–Al alloy system are more complicated than those of the silicon bearing system. Thus, special inoculation technique and feeding arrangement need to be adopted to produce spheroidal graphite aluminium cast iron.