Initial stage of isothermal decomposition of austenite to ferrite and graphite in spheroidal graphite cast Iron

Abstract EN

-Isothermal decomposition of austenite to ferrite and graphite in a spheroidal graphite cast iron nm investigated hv dilatometry, metallography and image analysis.

This gave quantitative, although indirect, information on the kinetics of carbon transfer from austenite to graphite, as well as on the kinetics of the austenite to ferrite and graphite transformation.

The relations of these kinetics with the graphite nodule count was pointed out.

The incubation period before ferrite growth was observed to he associated to a global contraction of the material, in spite of the related increase of the graphite volume fraction.

Calculations showed a good agreement with experimental results, except for the rale of carbon transfer, which is found to be much slower experimentally than predicted by calculations based on volume diffusion of carbon.

Possible reasons for this discrepancy are discussed.