Complex Widmanstätten plates consisting of cementite and ferrite, product phases of a eutectoid reaction, in an Fe-C-Mn alloy

► Complex Widmanstätten plates of M3C and ferrite in an Fe-C-Mn alloy were discovered. ► M3C appears in the austenite as grain boundary precipitates or Widmanstätten plates. ► Complex Widmanstätten plates have some characteristics similar to inverse bainite. ► Pearlite nodules exist at the austenite grain boundaries of the high manganese steel.