Formation and functional properties of Fe-based bulk glassy alloys

Ferromagnetic bulk glassy alloys were synthesized in a variety of alloy systems 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 alloys exhibit a large supercooled liquid region exceeding 50 K before crystallization and the largest value reaches approximately 100 K. The maximum sample thickness of glass formation in the alloy systems belonging to the groups (1) to (5) is about 3 mm, 12 mm, 6 mm, 1 mm and 3 mm, respectively. These 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 except for hard magnetic properties only for the Nd- or Pr-based alloys. In addition, the application of the consolidation technique using the viscous how phenomenon to the Fe-(AI, Ga)-(P, C, B) alloys caused the formation of fully 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 maximum permeability and 0.1 W/kg at 50 Hz for core loss. The combination of good magnetic properties, high glass-forming ability and good workability into a bulk form is promising the future development as a new type of magnetic material.