Formation and functional properties of Fe-based bulk glassy alloys

Ferromagnetic bulk glassy alloys were synthesized in a variety of alloy sys tems by the copper mold casting process for the last five years after 1995. Their typical alloy systems are classified into five groups, i.e., (1) Fe- (Al, Ga)-(P, C, B) and Fe-Ga-(P, C, B), (2) (Nd, Pr)Fe-(Al, Si), (3) Fe-(Zr , Hf,Nb)-B, (4) Fe-Co-Ln-B, and (5) Fe-(Cr, Mo)-B-C. The Fe-based glassy al loys exhibit a large supercooled liquid region exceeding 50 K before crysta llization and the largest value reaches approximately 100 K. The maximum sa mple thickness of glass formation in the alloy systems belonging to the gro ups (1) to (5) is about 3 mm, 12 mm, 6 mm, 1 mm and 3 mm, respectively. The se bulk glassy alloys exhibit good soft magnetic properties with a maximum saturation magnetization of 1.3 T and low coercive forces below 5 A/m excep t for hard magnetic properties only for the Nd- or Pr-based alloys. In addi tion, the application of the consolidation technique using the viscous how phenomenon to the Fe-(AI, Ga)-(P, C, B) alloys caused the formation of full y dense bulk glassy alloys with rather good soft magnetic properties, e.g., 1.2T for saturation magnetization, 10 A/m for coercive force, 9000 for max imum permeability and 0.1 W/kg at 50 Hz for core loss. The combination of g ood magnetic properties, high glass-forming ability and good workability in to a bulk form is promising the future development as a new type of magneti c material.