STUDY OF THE FAULTS STACKINGS IN THE GAMMA(FCC)[--]EPSILON(HCP) MARTENSITIC-TRANSFORMATION

The shape memory effect exhibited by Fe-Mn-Si based alloys is due to t he gamma(f.c.c.)-epsilon(h.c.p.) martensitic transformation. The marte nsitic transformation induced by traction at room temperature in a Fe- 16Mn-9Cr-5Si-4Ni (%mass) is here studied by optical microscopy, scanni ng electron microscopy, transmission electron microscopy and scanning tunnelling microscopy. The martensitic microstructure and the fine str ucture of the Faults stackings are both studied to clarify the nucleat ion and growth mechanisms of martensite. The band structure of the mar tensite is pointed out. Inside a grain, the monopartial nature of the martensite have been demonstrated from the elementary plate to all the martensite bands. From all the observations, the pole mechanism appea rs to be the main mechanism of martensite nucleation.