The austempered ductile cast iron from the critical zone, named NAZC in this work, has been presented as an emerging material due to its interesting range of mechanical properties. The main objective of this study is to evaluate the austenitizing parameters for NAZC manufacturing. Initially, ductile iron specimens were austenitized within the critical zone and quenched to evaluate the amount of austenite (martensite at room temperature), which would become ausferrite later in the study of austempering. The treatment of austempering results in a microstructure consisting of ausferrite and proeutectoid ferrite. From the analysis of quenching results, austempering treatments were performed and then the parameters that lead to certain microstructure were observed. In both treatments, the specimens were characterized by optical microscopy and image analysis. Austempering treatments performed at a temperature of 790°C and intervals of 3 h and 4 h led to a final microstructure which should present an interesting set of mechanical properties.