The Observation of the Structure of M23C6/γ Coherent Interface in the 100Mn13 High Carbon High Manganese Steel

The M23C6 carbides precipitate along the austenite grain boundary in the 100Mn13 high carbon high manganese steel after 1323 K (1050 A degrees C) solution treatment and subsequent 748 K (475 A degrees C) aging treatment. The grain boundary M23C6 carbides not only spread along the grain boundary and into the incoherent austenite grain, but also grow slowly into the coherent austenite grain. On the basis of the research with optical microscope, a further investigation for the M23C6/gamma coherent interface was carried out by transmission electron microscope (TEM). The results show that the grain boundary M23C6 carbides have orientation relationships with only one of the adjacent austenite grains in the same planes: . The flat M23C6/gamma coherent interface lies on the low indexed crystal planes {111}. Moreover, in M23C6/gamma coherent interface, there are embossments which stretch into the coherent austenite grain gamma. Dislocations distribute in the embossments and coherent interface frontier. According to the experimental observation, the paper suggests that the embossments can promote the M23C6/gamma coherent interface move. Besides, the present work has analyzed chemical composition of experimental material and the crystal structures of austenite and M23C6, which indicates that the transformation can be completed through a little diffusion for C atoms and a simple variant for austenite unit cell.