Moessbauer and X-ray diffraction study of isothermal ageing effect at 500 deg C in electrochemically deposited Fe-Ni-Cr alloys

Moessbauer spectroscopy, X-ray diffractometry and microprobe analysis were used to study electrodeposited Fe-Ni-Cr (40-50% Fe, 40-47% Ni, 3-5% Cr) alloys isothermally aged at 500 deg C from 5 minutes to 100 hours in an inert argon gas atmosphere. The main phase of the as-deposited samples exhibits ferromagnetic microcrystalline behavior, whereas the thermally prepared samples of same composition are always paramagnetic. The dominant effect of ageing is an oxidation process which resulted in the formation of hematite and magnetite iron oxides in considerable amounts and which are attributable to the presence of oxygen inclusions in the as-electrodeposited samples. (author)