Abstract austenite domain at 840  C. The slow cooling of these specimens led to the a-ferrite ? c0-Fe4N pearlitic microstructure which is similar to the pearlite in Fe–C binary system. This pearlitic microstructure has been characterized by electron microscopy. The crystal structure of the c0-Fe4N nitride has been identified by electron microdiffraction and the Nishiyama–Wassermann (N–W) and near Kurdjumov–Sachs (K–S) orientation relationships have been found between the a-ferrite and the c0-Fe4N.