Enhancement of soft magnetic properties by nanocrystallization in modified cast iron

A cast iron composition has been modified by additions of Al, B, Y and Cu to the Fe-C master alloy in order to achieve glass forming ability as well as good magnetic properties. Amorphous ribbons were synthesized by rapidly quenching at 106 K/s and the devitrification process was controlled by varying the Y and Cu contents so as to achieve a composite structure of bcc Fe nanocrystals in an amorphous matrix. An improvement of saturation magnetization was observed by annealing the as-quenched ribbons. However, coercivity does not necessarily improve upon annealing, and therefore, the annealing should be judiciously scheduled. Effect of minor impurities in cast iron on the coercivity and saturation of these alloys was found to be insignificant.