Deformation induced martensite characteristics in Fe-29Ni-2Mn alloy

Deformation induced martensite characteristics in the austenite phase of Fe-29Ni-2Mn alloy were studied for different austenite grain sizes of alloy. Scanning electron microscopy, transmission electron microscopy, Mossbauer spectroscopy and also differential scanning calorimetry techniques were applied to study in order to clarify the deformation induced martensite characteristics from morphological, crystallographical, magnetical and thermal points of view. Scanning electron microscope revealed that the increasing of deformation amount also increased the amount of existed martensite. Transmission electron microscope observations showed that the crystal structure of these deformation induced martensites morphology was lenticular plates with a bcc crystal structure. Also the magnetism of both austenite and martensite phases were determined with Mossbauer spectroscopy. Mossbauer spectrometer measurements showed paramagnetic character for austenite phases and ferromagnetic character for martensite phases in all samples. According to obtained differential scanning calorimetry cooling curves, deformation induced martensite start temperature M-d was found to be higher (-128 degrees C) for larger grained samples than for smaller grained samples (-135 degrees C).