Search

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 thermally induced γ–ɛ and γ–α′ martensitic transformation in Fe–30%Ni–x%Mo alloys with different Mo contents have been studied by transmission electron microscopy (TEM). Observations reveal that α′ martensite is found in alloys containing 0.8, 1.8, and 2.6% Mo, and ɛ martensite in the alloy containing 5%Mo. The first three display the Kurdjumov–Sachs (K–S) orientation relationship between γ and α′, while the other displays the Shoji–Nishiyama (S–N) orientation relationship between γ and ɛ. [Copyright &y& Elsevier]