Muneo Oka

Long Period Stacking Order Structures Formed by Thermal Cycles in an Fe-Mn-C Alloy

Crystal structures appearing in an Fe-16.50 wt % Mn (16.74 at %)-0.26 wt % C (1.23 at %) alloy subjected to cyclic cooling and heating (-196°C\rightleftarrows400°C) are investigated by means of transmission electron microscopy. A new long period stacking order structure, which is expressed as 15R and (3)3 in terms of the Ramsdell notation and the Zhdanov symbol respectively, is found in this alloy in addition to the 18 R (5)3 long period stacking order structure previously found by Lysak and Nikolin. The lattice parameters of the 15 R and 18 R structures and the orientation relationships between each structure and their matrix γ are obtained.