Microstructure evolution of Dy69Ni31-added Nd-Fe-B sintered magnets during annealing
Microstructure evolution of Dy69Ni31-added Nd-Fe-B sintered magnets during annealing
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DOI：
10.1016/j.jmmm.2019.165260
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发表时间：
2019-09
影响因子：
2.7
通讯作者：
Xiaolian Liu;Yujing Zhang;Pei-bin Zhang;T. Ma;M. Yan;Lizhong Zhao;Lingwei Li
中科院分区：
文献类型：
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作者：
Xiaolian Liu;Yujing Zhang;Pei-bin Zhang;T. Ma;M. Yan;Lizhong Zhao;Lingwei Li
在晶间添加含Dy粉末可有效提高nd2fe14b基烧结磁体的矫顽力，但由于在2:14:1晶粒周围形成（Nd, Dy）2Fe14B硬化壳，导致磁体的剩余物损失较小。本文研究了烧结后退火（PSA）时间对添加了Nd-Fe-B的dy69ni31磁体显微结构和矫顽力的影响。随着580 ℃退火时间的延长，当退火时间小于6 h时，矫顽力从10.1 kOe迅速增加到16.2 kOe，延长退火时间后，矫顽力基本保持不变。延长退火时间有利于形成更厚的富dy 2:14:1硬化层和优化的连续晶界层，对矫顽力的增强有积极的贡献。然而，透射电镜（TEM）研究表明，随着PSA时间的延长，三结处re -氧化物的晶体结构发生了变化，从双六边形紧密堆积（d-hcp）转变为面心立方（fcc）和有序体心立方（bcc）的混合物，再转变为六边形紧密堆积（hcp）。后一种转变可能对矫顽力增强起负作用，抵消了正作用。这些研究结果可为Nd-Fe-B烧结磁体的微观结构的工程化提供有益的指导。
Intergranular adding Dy-containing powders is effective to enhance the coercivity of Nd2Fe14B-based sintered magnets with slight remanence loss due to the formation of (Nd, Dy)2Fe14B hardening shell surrounding the 2:14:1 grains. Here, the influences of post-sinter annealing (PSA) time on microstructure and coercivity of Dy69Ni31-added Nd-Fe-B magnets have been investigated. With prolonging the annealing time at 580 °C, the coercivity increases rapidly from 10.1 kOe to 16.2 kOe when the annealing time is less than 6 h and keeps nearly unchanged after longer time annealing. Longer time annealing promotes the formation of thicker Dy-enriched 2:14:1 hardening shells as well as optimized and continuous grain boundary (GB) layers, which plays positive contributions to enhance coercivity. However, the transmission electron microscope (TEM) investigations reveal that crystal structure of RE-oxides at the triple junctions changes with prolonging PSA time, transforming from double hexagonal close-packed (d-hcp) to a mixture of face-centered cubic (fcc) and ordered body-centered cubic (bcc) and to hexagonal close-packed (hcp). The latter transformation may play a negative role on coercivity enhancement, offsetting the positive contributions. These findings may provide a useful guide for engineering the microstructure of Nd-Fe-B sintered magnets.