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

Complex Widmanstätten plates of cementite and ferrite, product phases of a eutectoid reaction, in an Fe–10.6 Mn–0.64 C steel have been investigated. Different forms of proeutectoid M3C carbide appear in the austenite as grain boundary precipitates or Widmanstätten plates in the austenite at temperatures below 1048 K. Some Widmanstätten plates may consist of lamellar cementite and ferrite as complex Widmanstätten plates at temperatures below 1023 K. Aside from the complex plates, pearlite nodules exist at the austenite grain boundaries at temperatures below 973 K. Therefore, the lamellar cementite and ferrite in both complex Widmanstätten plates and pearlite nodules are all product phases from the eutectoid reaction. The upper temperature limit for the eutectoid reaction is between 1023 K and 973 K. The complex Widmanstätten plates have some characteristics similar to inverse bainites, but appear at much higher temperatures, near the eutectoid temperature of the steel.