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Öğe Characterization of martensite in Fe-25%Ni-15%Co-5%Mo alloy(Pergamon-Elsevier Science Ltd, 2009) Sarı, Uğur; Güler, E.; Kırındı, Talip; Dikici, MineKinetic, morphological, crystallographical, magnetic and thermal characteristics of thermally induced martensite in Fe-25%Ni-15%Co-5%Mo, alloy have been investigated by scanning electron microscope (SEM), transmission electron microscope (TEM), Mossbauer spectrometer, and differential scanning calorimeter (DSC). Kinetics of the transformation was found to be athermal. Also only lenticular martensite morphology was observed during microscope observations. in addition, martensite start temperature (M(s)) was determined as -63 degrees C from differential scanning calorimeter. On the other hand, Mossbauer spectra revealed a paramagnetic character for the austenite phase and a ferromagnetic character for thermally induced martensite phase. (C) 2009 Elsevier Ltd. All rights reserved.Öğe Comparison of thermally induced and deformation induced martensite in Fe-29% Ni-2% Mn alloy(Elsevier Science Sa, 2007) Güler, E.; Kirindi, T.; Aktas, H.The morphology and crystallography of maitensite either formed by cooling to subzero temperatures (thermal effect) or by compression deformation were compared for different austenite grain sizes of Fe-29% Ni-2% Mn alloy by transmission electron microscope (TEM). TEM observations revealed both epsilon and alpha' martensite formation within large grained austenite phases by thermal effect whereas only alpha' martensite formation was observed in small grained austenite phases. On the other hand, compression deformation effect caused only a' martensite formation in both small and large grained austenite phases of Fe-29% Ni-2% Mn alloy. Thermally induced alpha' martensite exhibited a lenticular morphology with partial twinnings that are peculiar to this kind of morphology. The crystallographic orientation relationship between austenite and thermally induced alpha' lenticular martensites was found to be as Kurdjumov-Sachs (K-S) type relationship. (c) 2006 Elsevier B.V. All rights reserved.Öğe Deformation induced martensite characteristics in Fe-29Ni-2Mn alloy(Taylor & Francis Ltd, 2008) Güler, E.; Aktas, H.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).Öğe Effects of homogenization time on the both martensitic transformations and mechanical properties of Fe-Mn-Si-Cr-Ni shape memory alloy(Elsevier Science Sa, 2007) Kirindi, T.; Güler, E.; Dikici, A.In this work, we have investigated some physical and mechanical properties of martensitic transformation in Fe-12.5%Mn-5.5%Si-9%Cr-3.5%Ni (wt) shape memory alloy. Compressive deformation at room temperature, which applied to epsilon(hcp) phase within austenite phase cause the formation of alpha'(bcc) martensite crystals at intersection of prior e martensite plates and also new formed 8 martensite plates were observed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction methods were applied for revealing microstructural and crystallographic features of martensitic transformations in this alloy. Also effect of prior homogenization time on the martensitic transformations and their mechanical features were stress-strain curves. (c) 2006 Elsevier B.V. All rights reserved.Öğe Mossbauer studies on athermal martensite formation in an Fe-Ni-Mn alloy(Indian Academy Sciences, 2002) Aydin, A.; Güler, E.; Aktas, H.; Gungunes, H.In this study, austenite-martensite phase transformations which are formed by cooling effect in Fe-30% Ni-0.2% Mn alloy are investigated with Mossbauer spectroscopy and scanning electron microscopy. The single peak of the paramagnetic phase and the six peaks of the ferromagnetic phase of Fe-30% Ni-0.2% Mn alloy were observed in the Mossbauer spectrum. The internal magnetic field strength of ferromagnetic martensite phase was. determined as 33.8 T and the isomer shift values were determined as - 0.11 mm(.)sec(-1) and - 0.06 mm.sec(-1), respectively, for the austenite and martensite phases. In this alloy, athermal transformation was observed. The results obtained are in agreement with literature.Öğe Some aspects of thermally induced martensite in Fe-30% Ni-5% Cu alloy(Elsevier Science Bv, 2007) Güner, M.; Güler, E.; Yaşar, E.; Aktaş, H.Kinetical, morphological, crystallographical and several thermal properties of thermally induced martensite in the austenite phase of Fe-30% Ni-5% Cu alloy were investigated. Scanning electron microscope (SEM), transmission electron microscope (TEM) and differential scanning calorimetry (DSC) techniques were used during study. Kinetics of the transformation was found to be as athermal type. SEM and TEM observations revealed alpha' (BCC) martensite formation in the austenite phase of alloy by thermal effect. These thermally induced alpha' martensites exhibited a thin plate-like morphology with twinnings. (C) 2007 Elsevier B.V. All rights reserved.
