Microstructural evolution and deformation mechanism of a Fe-15Mn alloy investigated by electron back -scattered diffraction and transmission electron microscopy

The present studies focus on mechanical properties and microstructure evolution of a Fe-15Mn dual phase alloy during tensile deformation based on the analyses of X-ray diffraction, electron back-scattered diffraction and transmission electron microscopy. The alloy possesses excellent combination of strength and ductility (UTS x TEL =32 GPa.%) and good strain hardening capacity owing to several plastic deformation mechanisms. At earlier stage of tensile deformation, the deformation induced transformation from gamma to epsilon is the main plastic deformation mechanism. In addition, the deformation induced twins within epsilon-martensite and transformation from e to a also have contributions to the plastic deformation. With further increasing the strain, the deformation induced transformation from epsilon ->alpha' in combination with the dislocation slip in gamma, epsilon and alpha' become the main plastic deformation mechanisms. During the whole tensile deformation, nearly all alpha'-martensite grains exist within epsilon-martensite plates, indicating that the deformation induced transformation sequence is Moreover, it has been demonstrated that the alpha'-martensite is preferred to nucleate at intersections of two emartensite plates, interfaces of gamma/epsilon and epsilon/epsilon and low angle grain boundaries within epsilon-martensite plates. Note that the orientations of some alpha'-martensite grains existing within the same s-martensite plate are not exactly the same.