New YDy-Based R2(Fe,Co)14B Melt-Spun Magnets (R=Y+Dy+Nd)
The effects of the ratio of Y to Dy as well as the effect of Nd and Co substitutions on magnetic properties in [Ndx(YDy)0.5(1-x)]2.2Fe14-yCoyB ribbons melt-spun at 22 m/s have been systematically studied. (Y1-zDyz)2.2Fe14B 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 Nd2Fe14B ribbons. In [Ndx(YDy)0.5(1-x)]2.2Fe14-yCoyB 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 α and β are -0.07 and -0.31 %/°C in the temperature range of 27 to 127°C, respectively. Increasing Co (x) from 0 to 3, slightly decreases coercivity Hcj 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°C, respectively. Its α and β are -0.11 and -0.30 %/°C, 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°C.
Z.Y. Zhong, H. Saka, T.H. Kim, E.A. Holm, Y.F. Han and X.S. Xie
W. Tang et al., "New YDy-Based R2(Fe,Co)14B Melt-Spun Magnets (R=Y+Dy+Nd)", Materials Science Forum, Vols. 475-479, pp. 2155-2160, 2005