Precipitation and high temperature magnetic properties of FeCo-based alloys

The microstructure and high temperature magnetic properties of Fe-Co-2V and Fe-Co-2V-0.3Nb alloys have been investigated. Aging at 600°C, γ 2 phases precipitate whose size and volume fraction increase with increasing aging time. A roughly linear relationship between magnetic coercivity H c and volume fraction of the γ 2 precipitates was observed. Addition of Nb facilitates nucleation and growth of the γ 2 precipitates, resulting in a dramatic deterioration of soft magnetic properties of the alloys. A pinning effect of the γ 2 precipitates on the magnetic domain wall has been observed by Lorenz electron microscopy.