(Nd,Dy)-(Fe,Co)-B系急冷薄帯磁石およびそれらのボンド磁石の磁気特性

概要

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In melt-spun ribbons of (Nd, Dy)-(Fe, Co)-B system alloys prepared by the single roller method, the effects of composition, substrate surface velocity and subsequent annealing on the magnetic properties were studied, and their bonded magnets were made of the optimum-quenched ribbons. The maximum magnetic energy product of 94.4kJ/m^3 was obtained in Nd_<15>Fe_<79>B_6 ribbon prepared at a substrate surface velocity of 11.8m/s. In (Nd, Dy)-(Fe, Go)-B ribbons, the best magnetic energy product of 88.2kJ/m^3 was obtained in the composition (Nd_<0.975>Dy_<0.025>)_<15>(Fe_<0.9>Co_<0.1>)_<79>B_6 which contains Dy and Co to improve the temperature properties. X-ray diffraction patterns from samples of the highest coercivity show a mixture of an amorphous phase and a fine crystalline one. The maximum magnetic properties obtained in these bonded magnets of Nd_<15>Fe_<79>B_6 alloy were B_r=0.630 T, H_<CJ>=1232 kA/m, H_<CB>=412 kA/m and (BH)_<max>=65.60 kJ/m^3. The average temperature coefficients of B_r and H_<CB> between 298 and 398 K for these Nd_<15>Fe_<79>B_6 bonded magnets were -0.139%/K and -0.272%/K, respectively, and these values of (Nd_<0.975>Dy_<0.025>)_<15>(Fe_<0.9>Co_<0.1>)_<79>B_6 bonded magnets with (BH)_<max>=58.08 kJ/m^3 were α_<B_r>=-0.118%/K and α_<H_<CB>>=-0.200%/K. From these results it was known that the values of the temperature coefficient of Nd-Dy-Fe-Co-B bonded magnets were superior to those of Nd-Fe-B bonded magnets.