New YDy-based R_2(Fe,Co)_(14)B Melt-spun Magnets (R=Y+Dy+Nd)

摘要

The effects of the ratio of Y to Dy as well as the effect of Nd and Co substitutions on magnetic properties in [Nd_x(YDy)_(0.5(1-x))]_(2.2)Fe_(14-y)Co_yB ribbons melt-spun at 22 m/s have been systematically studied. (Y_(1-z)Dy_z)_(2.2)Fe_(14)B ribbons with a ratio z of 0.25 or 0.5 simultaneously obtains a smaller temperature coefficient of remanence (α) and coervicity (β) which are much smaller than those of Nd-based Nd_2Fe_(14)B ribbons. In [Nd_x(YDy)_(0.5(1-x))]_(2.2)Fe_(14-y)Co_yB ribbons, Nd substitution (x=0 to 0.8) can improve the maximum energy product (BH)_(max) of annealed ribbons but degrades the temperature stability of the magnetic properties. The ribbons with x=0.4 and y=0 yield a (BH)_(max) of 8.7 MGOe. For these ribbons, the a and p are -0.07 and -0.31 %/℃ in the temperature range of 27 to 127℃, respectively. Increasing Co (x) from 0 to 3, slightly decreases coercivity H_(CJ) from 21.5 to 16.3 kOe, but keeps the (BH)_(max) in the range of 8.6 to 10.2 MGOe. The optimal sample with x=0.5 and y=1.5 obtains a (BH)_(max) of 10.2 and 5.0 MGOe at 27 and 250℃, respectively. Its a and p are -0.11 and -0.30 %/℃, respectively. These results show that studied ribbons are very promising to develop into high temperature isotropic bonded magnets capable of operating at or above 180℃.