Preparation and soft magnetic properties of Fe-based bulk amorphous alloys

This review deals with our recent development of Fe-based bulk amorphous alloys with soft magnetic properties. Multicomponent Fe-(Al,Ga )-(P,C,B,Si) and Fe-(Co,Ni)-(Zr,Nb,Ta)-B alloys are amorphized in the bulk form with diameters up to 2 and 6 mm, respectively, by copper mold casting and the largest temperature interval of the supercooled liquid region before crystallization is 67 and 88 K, respectively. These bulk amorphous alloys exhibit good soft magnetic properties, i.e., high saturation magnetization (I s ) of 1.1 to 1.2 T and low coercivity (H c ) of 2 to 6 A/m. The saturated magnetostriction (λ s ) and Curie temperature (T c ) are in the range of 20-30×10 -6 and 580-605 K, respectively, for the former system and 10-14×10 -6 and 447-594 K, respectively, for the latter system. The effective permeability (μ e ) at 1 kHz is 7000-15000 for the Fe-(Al,Ga)-(P,C,B,Si) amorphous ribbons and 15000-25000 for the Fe-(Co,Ni)-(Zr,Nb)-B amorphous ribbons. In comparison with Fe-Si-B amorphous ribbons, it is characterized that the present alloys have lower H c and higher μ e resulting from lower λ s . The easy formation of bulk Fe-based amorphous alloys with good soft magnetic properties indicates the possibility of future development as a new type of soft magnetic material.