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The effect of austenitising temperature and cooling rate on the morphology and magnetic properties of martensite in Fe–24·5%Ni–4·5%Si alloy has been studied by means of scanning electron microscopy, Mössbauer spectroscopy and AC susceptibility. Martensite morphology was found to be closely dependent on the austenitising temperature and cooling rate. The changes in volume fraction of martensite and austenite phases, the internal magnetic field of martensite phase and the isomery shift values have been determined by Mössbauer spectroscopy. The Mössbauer study revealed that the martensite volume fractions increased with increasing austenitising temperature and cooling rate. Also internal magnetic field of martensite was decreased by increasing the martensite volume fractions. AC magnetic susceptibility measurements showed that the Neel temperatures TN and the magnetic susceptibility χ increase with increasing austenitising temperatures. [ABSTRACT FROM AUTHOR]

Abstract: The paramagnetic–magnetically ordered transition and the effect of Mo content on the magnetic properties of martensite phase in Fe–30% Ni–x% Mo alloys have been investigated by AC susceptibility and Mössbauer spectroscopy. The results show that martensitic transformation temperature (M S) indicates the magnetic transition from paramagnetic to magnetically ordered state. Hyperfine magnetic field, isomery shift and volume fractions of phases were determined by Mössbauer spectroscopy. It is also found that volume fraction of thermally induced martensite and M S temperature decreased with the increasing Mo content. [Copyright &y& Elsevier]