Materials properties and utilization of Fe_3B/Nd_2Fe_(14)B-type nanocomposite permanent magnets based on Nd-Fe-Cr-Co-B

摘要

Recent progresses of materials development and their utilization of Cr-and-Co-doped Fe_3B/Nd_2Fe_(14)B-type nanocomposite permanent magnets are reported. A practical balance between enhanced intrinsic coercivity and temperature stability of magnetic properties has been realized by simultaneous additions of Cr and Co. This type of magnets are less susceptible o oxidation because of the less rare-earth content. Consequently, even fine powders (e. g., under 38 micrometer sieve) are physically and chemically stable in contrast to the conventional Nd_2Fe_(14)B-type melt-spun materials. The stability in terms of the structural losses is also superior to that of the Nd_2Fe_(14)B-type melt-spun materials. Utilization of the Cr-and-Co-doped Fe_3B/Nd_2Fe_(14)B nanocomposite permanent magnets as a hard magnetic component of injection-molded resin-bonded magnets seems promising because of the excellent stability of the magnetic properties of fine powders. Direct quenching of a melt into the nanocomposite structure has become possible recently in addition to the conventional processing route of crystallization of an amorphous precursor, opening up the possibility of less-expensive production of the material.