Thermo-Induced Phase Transformations in Mechanically Synthesized Nanocomposites Based on (Fe,Mn,Ni)75C25

The formation of phases in mechanically synthesized (Fe 0.90− x Mn 0.10 Ni x ) 75 C 25 alloys, where х = 0.05 and 0.10, is studied via X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. It is shown that certain products form during the mechanosynthesis of the initial powders in a planetary ball mill: cementite doped mainly with manganese, ferrite, and an amorphous phase doped mainly with nickel. Annealing at 500°C and higher temperatures leads to the formation of a composite consisting of cementite and austenite doped mainly with nickel. Cementite regions with two different Curie temperatures form as the alloys cool after high-temperature (700°C) annealing, due to differences in the manganese doping of cementite in these regions.