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    EFFECT OF MN AMOUNT ON PHASE TRANSFORMATIONS AND MAGNETIC PROPERTIES IN Fe-Mn-Mo-Si ALLOYS
    (Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2021) Armagan, Osman; Kirindi, Talip
    In this study, microstructural and crystallographic properties of phase transformations occurring with thermal effect in Fe-XMn-Mo-Si (X = 15.14wt.% ye 18.45wt.%) alloys have been investigated. The effects of (wt.%) Mn rates in the alloy on the characteristics of phase transformations were investigated by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). SEM and TEM investigations was observed that two different martensite (epsilon and alpha') structures were formed in austenite grain. In addition, in TEM observations, the interface regions were selected over the bright field image. Crystallographic orientation relationships were obtained by the analyses of electron diffraction patterns from the interface regions. gamma -> alpha' type transformation was observed for a' particle formation, and orientation relationship was found as ((1) over bar 11)(gamma)//(011)(alpha'), [101](gamma)// [(1) over bar1 (1) over bar](alpha'), and, gamma -> epsilon type transformation was observed for epsilon martensite plate formation, and the orientation relationship was found as ((1) over bar1 (1) over bar))(gamma),(000 (2) over bar)(epsilon), //[(1) over bar(1) over bar0](gamma)//[(2) over bar 110](epsilon). It was noticed that this orientation relationships were compatible with the literature (Kurdjumov-Sachs and Shoji-Nishiyama orientation relationship). Precipitation phase (carbide) formation was observed in microstructure analyses. The changes in the magnetic properties of the alloys having different rates of Mn as a consequence of thermal effect phase transformations was investigated by using Mossbauer Spectroscopy. The internal magnetic field, volume fractions (transformation rates), isomer shift values and magnetic characteristics of the main and product phases were revealed by Mossbauer Spectroscopy. In the Mossbauer Spectrum, it was noticed that epsilon-martensite and gamma-austenite structures showed paramagnetic single-peak, and alpha'-martensite showed ferromagnetic six-peaks.
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    Effects of thermal and deformation on martensitic transformation and magnetic properties in Fe-17%Mn-4.5%X (X = Co and Mo) alloys
    (Pergamon-Elsevier Science Ltd, 2017) Armagan, Osman; Sari, Ugur; Yucel, Cagri; Kirindi, Talip
    In this study, the Co and Mo addition to Fe-Mn based alloys was investigated to observe its effect on martensitic phase transformation. Two types of martensite structure occurred from the surface observations made by SEM for Co-added and Mo-added alloys morphologically in austenite grain. With the help of TEM studies, it was understood that these martensite structures are epsilon (h.c.p.) and alpha' (b.c.c.). TEM investigations showed that the orientation relationship between gamma (f.c.c.) and epsilon phases corresponds to Shoji-Nishiyama type and between gamma and alpha' phases corresponds to Kurdjumov-Sachs (K-S) type. In the SEM observations, the amount of these two types of martensite structure has been varied depending on the amount of deformation and the heat treatment temperature. In addition, Co and Mo effects were revealed in microstructure analyzes. By comparing the values of the lattice parameters obtained from the TEM and X-Ray observations with the values of those in the literature, it is shown how Co and Mo affect the lattice parameters of structure. The lattice parameter in Co-added alloy is a(alpha') = 2.8695 A degrees while Mo-added alloy is calculated as a(alpha') = 2.8567 A degrees. The type of martensitic transformation and the change of magnetic properties of alloys related to transformation rate were demonstrated by the analysis of the Mossbauer Spectrometer data. In particular, the change in the amount of alpha' martensite changes the antiferromagnetism or ferromagnetism and the internal magnetic field values of the alloys.