优化边界结构制备高矫顽力及高热稳定性烧结Nd-Fe-B磁体

PREPARATION OF SINTERED Nd-Fe-B MAGNET WITH HIGH COERCIVITY AND HIGH THERMAL STABILITY BY OPTIMIZING BOUNDARY MICROSTRUCTURE

用双合金工艺在(Nd_(0.75)D_(y0.10)Tb_(0.15))_(12.69)Fe_(79.01)Co_(2.00)Nb_(0.30)B_(6.00)近正分主合金粉中添加质量分数为3%的富稀土辅合金(Nd_(0.75)D_(y0.10)Tb_(0.15))_(25.00)Fe_(21.50)CO_(21.50)Nb_(4.00)Ga_(8.00)Ti_(5.00)Al_(8.00)B_(7.00)粉和3%的Dy_2O_3粉,成功制备出超高矫顽力和高热稳定性的烧结Nd-Fe-B磁体,内禀矫顽力H_(ci)和最大磁能积(BH)_(max)分别为3028kA/m和254 kJ/m^3,22—220℃剩磁和矫顽力的温度系数分别为-0.104%/℃和-0.356%/℃,260℃不可逆磁通损失L_(irr)的绝对值仅为4%.微观组织分析表明:主相Nd_2Fe_(14)B晶粒边界光滑、平直,富Nd相连续均匀分布于主相晶粒周围;在Nd_2Fe_(14)B晶粒表层附近富含Dy,Dy_2O_3中的Dy通过扩散与富Nd相及Nd_2Fe_(14)B晶粒表层中的Nd发生置换,从而在界面附近增强了磁各向异性.在此基础上,进一步提出了制备高矫顽力烧结Nd-Fe-B磁体中Dy的理想分布示意图.

Sintered Nd-Fe-B magnet with super-high coercivity and high thermal stability has been synthesized by blending 3%Dy2O3 powder and 3% （Ndo.75Dy0.10Tb0.15）25.00Fe21.50Co21.50Nb4.00- Ga8.00Ti5.00Al8.00B7.00 powder （mass fraction） to near stoichiometric （Nd0.75 Dy0.10Tb0.15） 12.69Fe79.01- Co2.00Nb0.30B6.00 main alloy powder. The intrinsic coercivity Hci of the magnet reaches 3028 kA/m, the maximum energy product （BH）max reaches 254 kJ/m3, the temperature coefficients （from 22-- 220 ℃） of remanence and intrinsic coercivity reach -0.104%/℃ and -0.356%/℃, respectively, and irreversible flux loss at 260℃ is only 4%. SEM indicated that the Nd2Fe14B grain boundaries are smooth and straight, and the distribution of Nd-rich phase around Nd2Fe14B grain is continuous and uniform. Dy element segregates near the surface layer of Nd2Fe14B grains, indicating Dy in Dy2O3 powder diffused and substituted Nd elements in Nd-rich phase and the surface layer of Nd2Fe14B grain, which increased magnetic anisotropy of boundary of Nd2Fe14B grain only and depressed the nucleation and expansion of reverse magnetization domain. Furthermore, an ideal model of Dy distribution in Nd-Fe-B sintered magnets with high intrinsic coercivity was presented.