Effects of Additional Alloying Elements on Structures and Properties of Rare Earth-Iron-Boron Type Magnets

概要

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Changes in microstructures and properties of rare earth-iron-boron type magnet alloys on addition of small amounts of a fourth element have been investigated with electron probe micoanalyses, differential thermal analyses, microhardness measurements and microstructure studies. The coercivity in both the sintered Nd-Fe-B magnet and the cast-hot-pressed Pr-Fe-B magnet is nucleation-controlled rather than pinning-controlled. The III b family element such as Al or Ga is added as a fourth element of sintered Nd-Fe-B magnet aloy. On the other hand, the I b family such as element Cu or Ag is chosen as a fourth element of cast and hot-pressed Pr-Fe-B magnet alloy. Small amounts of Al or Ga dissolve into Nd_2Fe_<14>B phase, while Cu and Ag do not dissolve into Pr_2Fe_<14>B phase. Al and Ga do not dissolve into Nd_<1.1>Fe_4B_4 phase. As microhardness of Nd_<1.1>Fe_4B_4 phase is very hard, R_2Fe_<14>B magnet alloy with lesser B is desirable in cast and hot-pressed magnet alloy. Each addition of Cu or Ag lowers the eutectic temperature of alloys and is effective in improving hot-workability of magnet alloys.
東海大学の論文