Abstract
For the development of advanced steels, phase transformation from ferrite(α) to austenite(γ) is essentially important to control the austenite phase in the heating process. Formation of austenite during the initial stage of α→γ transformation from the recrystallized ferrite in low carbon steel has been studied from the view-point of the orientation relationships and the interphase boundary structure. At high temperature, the in situ electron backscattering diffraction (EBSD) analysis of austenite grain growth during the α→γ transformation indicates that the different migration behaviors according to different α/γ interfaces, derive from the interfacial coherency with the specific orientation relationships. The orientation and microstructure of the interface between ferrite and austenite have been investigated using the 3D crystal orientation analysis and transmission electron microscopy (TEM) observations. When the crystal orientation relationship between ferrite and austenite grain are close to the Kurdjumov–Sachs relationship, the grain boundary normal itself is also close to the {111}α and {011}γ, respectively. The microstructure of these interfacial planes is revealed to be flat using 3D-EBSD and TEM analysis. These coherent planes are strongly connected to the formation of the austenite phase on heating and also affect the slow migration of the grain-growth process.
