纳米双相Nd_2Fe_(14)B/α-Fe磁体的微结构和交换耦合作用

Microstructure and exchange coupling interaction of nanocomposite Nd_2Fe_(14)B/α-Fe magnets

用熔体快淬法制备了高性能纳米双相耦合Nd2 Fe14 B/α Fe磁体 ,研究了快淬速率对其微结构和交换耦合作用的影响。实验结果表明 ,控制快淬速率在 12m/s时 ,可直接得到显微组织均匀 ,α Fe相粒子细小且均匀分布的纳米双相耦合Nd2 Fe14 B/α Fe磁体。低温退火消除由快速凝固带来的成分不均匀性后 ,强烈的铁磁交换耦合作用导致其最高磁性能为 :iHc=432 .2kA/m ,Jr=1.0 8T ,(BH) max=115kJ/m3 。快淬速率提高 ,非晶相体积分数增加 ,在高温晶化热处理时软硬磁相析出不均匀 ,个别α Fe相粒子奇异长大 ,尺寸达到 10 0nm左右 ,这不利于软硬磁相间的交换耦合作用 ,有损磁性能。

Nanocomposite Nd 2Fe 14 B/α-Fe magnets are synthesized by melt-spinning a Nd 8Fe 86 B 6 alloy and the effect of wheel speed on the microstructure and exchange coupling interaction is investigated. The results show that there is an optimum wheel speed about 12 m/s at which a homogeneous Nd 2Fe 14 B/α-Fe microstructure with fine α-Fe grains is developed directly from the melt. After low temperature annealing, the non-uniform composition from amorphous is eliminated and the magnetic properties can increase. The maximum magnetic properties are: i H c=432.2 kA/m, J r=1.08 T, (BH) max =115 kJ/m 3. However, higher wheel speed leads to the appearance of amorphous phase and its volume fraction increases with the increase of wheel speed. These result in a Nd 2Fe 14 B/α-Fe structure with large α-Fe grains after a subsequent crystallization annealing, which deteriorates the exchange-coupling between Nd 2Fe 14 B phase and α-Fe phase and decrease its magnetic properties.