Effects of annealing on the magnetic properties of Fe-6.5%Si alloy powder cores

Powder compressed cores can overcome poor workability of Fe-6.5%Si alloys. In this study, effects of annealing temperature on the losses of Fe-6.5%Si powder compressed cores were investigated. The hysteresis loss was two to three times larger than the eddy current loss. With the increasing annealing temperature, the hysteresis loss decreased due to a residual stress relief. With increasing the temperature, on the contrary, the eddy current loss increased even though the resistivity increased abruptly. An increase of the eddy current loss with the temperature can be understood by coarsening of DO(3) phase. It was thought that controlling the microstructure of the powders is more important than that of resistivity. It is also very effective to anneal the powders at a temperature higher than 1000 degrees C in order to reduce the total loss further. (c) 2008 American Institute of Physics.