TEM and HREM study on the fine structure and the interfacial structure of bainite

The fine structure of bainite, the morphology and distribution of carbide in steels and the morphology of bainite in Cu-Zn-Al alloys have been investigated with TEM. The interfacial structure ledges and interfacial crystal lattice images of Cu-Zn-Al alloys have also been investigated with HREM. The addition of alloying microelements can fine the structure of bainitic ferrite markedly. The bainitic ferrite is composed of subunits or subchunks. The carbides differ in morphologies and are distributed in between laths, inside the plates and on the boundaries of subunits. There are abundant fine structures in bainitic ferrite. In the primary bainite of Cu-Zn-Al alloy there are interfacial structure ledges, the height of which is about 3-40 nm, equal to 15-200 atomic layers. The phase transformation mechanism of bainite is discussed.