Nanocrystallization by nitriding treatment of FeSiB-based amorphous ribbons

In FeSiB-based systems, nanocrystalline state needed for good soft magnetic properties is obtained by controlling nucleation and growth rates of crystallization. These rates are known to depend on the additive elements in the FeSiB alloys but also on the annealing treatment. Generally, Cu and Nb are chosen as additive elements and conventional thermal treatment (C.T.T.) is used to produce the nanocrystalline phase. In this work, we studied Fe 73.5 Cu 1 Si 13.5 B 12 , Fe 74 Nb 3 Si 14 B 9 and Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 ribbons. To obtain the nanocrystalline state, in addition to C.T.T., we used a nitriding thermochemical treatment (N.T.T.) at 520°C and we show that this treatment improves the nanocrystalline state (smaller grain size D and higher crystalline volume fraction). This treatment also increases the Curie temperature of the crystalline α-FeSi phase.