The isothermal decomposition of austenite to ferrite plus graphite in a spheroidal graphite cast iron was investigated by means of dilatometry, metallography and image analysis. The results furnished quantitative information concerning the kinetics of C transfer from austenite to graphite, as well as the kinetics of the austenite to ferrite plus graphite transformation. The relationships between these kinetics, and the graphite nodule count, was emphasized. The incubation period before ferrite growth was found to be associated with a global contraction of the material, in spite of a related increase in graphite volume fraction. The calculations were in good agreement with experimental results, except with regard to the rate of C transfer. This was found to be much slower experimentally than was predicted by calculations that were based upon the volume diffusion of C.

Carbon Diffusion and the Decomposition of Austenite to Ferrite and Graphite in a Spheroidal Graphite Cast Iron. F.Hellal, J.Lacaze, A.Hazotte: Canadian Journal of Physics, 1999, 77[9], 677-84