Critical temperature range in standard and Ni-bearing spheroidal graphite cast irons

Describing the conditions for reaustenitization of spheroidal graphite cast irons is of interest for theirheat-treatment after casting, e.g. for manufacturing austempered ductile irons. Differential thermal analy-sis has been used to characterize the direct eutectoid transformation and the reverse transformation, i.e.the reaustenitization. This has been applied to a standard and a Ni-bearing alloy, with a ferritic matrix forthe former, both a ferritic and a pearlitic matrix for the latter. The results are discussed in relation with thestable and metastable three phase fields. While earlier description of the direct eutectoid transformationis confirmed, the one for reverse eutectoid has been found more complex and is amended.