摘要
采用传统的粉末冶金方法制备了名义成分为Nd_(28)Dy_2Fe_(68.6)B_1Ga_(0.2)Nb_(0.2)的烧结钕铁硼磁体,并研究了烧结钕铁硼磁体Nd_(28)Dy_2Fe_(68.6)B_1Ga_(0.2)Nb_(0.2)晶粒的细化和磁体晶界相演化之间的关系。通过细化磁粉粒度,制备出了平均晶粒尺寸分别是8.22,4.69,3.60和3.12μm的4种磁体。结果表明,磁体平均晶粒尺寸为3.60μm时对应的磁体的磁性能最好:最大磁能积(BH)m=389.93 k J·m^(-3),内禀矫顽力Hcj=1282.79 k A·m^(-1)。从磁体的微观形貌观察发现,随着磁体平均晶粒尺寸的减小,磁体中角隅晶界相的尺寸减小,条带状晶界相的比例增大,使更多的富Nd相参与到隔断主相晶粒之间的磁交换耦合中来,磁体矫顽力提高。磁粉粒径细化之后,磁粉颗粒的形貌更加规则、均一,取向时受到的摩擦力减小,提高了磁体的剩磁和取向度。但是随着平均晶粒尺寸从3.60到3.12μm的进一步减小,富Nd相发生了团聚,且分布不均匀,导致磁体矫顽力降低;磁体中的富Nd相增多并团聚,导致了磁体在烧结过程中由于液相较多而使主相晶粒发生了偏转,而且导致了磁体取向度降低,进而导致剩磁的减小。
The sintered permanent magnets, with the nominal composition of Nd28 Dy2Fe68 6 B1 Ga0.2 Nb0.2, were prepared using con- ventional powder metallurgy method. The correlation between refined grains and micro structural evolution of grain boundary phase in Nd28Dy2Fe68.6B1 Ga0.2 Nb0.2 sintered magnets was investigated. Four kinds of sintered magnets, with different average grain sizes of 8.22, 4.69, 3.60 and 3.12 μm, were prepared through refining magnetic powder particle size. The results showed that the sintered magnet with an average grain size of 3.60 μm showed the optimal magnetic properties, the maximum magnetic energy product （BH） m = 389. 93 kJ·m-3 , intrinsic coercivity Hcj = 1282.79 kA ·m-1. With the decrease of the average grain size, the size of corner grain boundaries reduced, and the proportion of banded grain boundaries increased, resulting in more Nd2 Fe14 B grains being surrounded by the Nd-rich phase, which improved the intrinsic coercivity. With the decrease of particle size of magnetic powder, the particles were regular and homogeneous, which suffered weak friction during molding process, and improved the remanence and orientation degree of magnets. But with the average grain size further decreasing from 3.60 to 3.12 μm, the Nd-rich phase assembled and distributed unevenly, resulting in the decrease of coercivity. Besides, in the magnets, because the Nd-rich phase increased and assembled, the main phase grain deviated from c-axis during the sintering process due to the increasing liquid phase, bringing about the decrease of orientation degree of magnets and then the decrease of remanence Br.
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2015年第11期988-992,共5页
Chinese Journal of Rare Metals
基金
国家科技部"973"计划项目(2014CB643701
2010CB934601)
国家科技部"863"计划项目(2011AA03A401)
国家自然科学基金项目(50931001
51271060
51171049)资助
关键词
细化晶粒
烧结钕铁硼
内禀矫顽力
晶界相
refined grain
NdFeB sintered magnets
intrinsic coercivity
grain boundary phase
