Further studies of the miscibility gap in an Fe-Cr-Co permanent magnet system

The miscibility gap of an Fe-Cr-Co system is further examined by monitoring the microstructures and the magnetic properties of the alloys. It is shown that the shape of the miscibility gap is not parabolic but of a peculiar shape, protruding to the Fe side along the Curie temperature. The part of the protrusion of the miscibility gap is called the "ridge" because of its shape resemblance. It is demonstrated that the alloys in the ridge region can exhibit very good magnetic properties. An Fe-25%Cr-12%Co alloy gives the magnetic properties as T(14.5 kG), kA/m (630 Oe) and (BH)max = 61.3 kJ/m³(7.7 MG . Oe), which are almost comparable to those of the columnar Alnico 5 magnets.