The Role of Cu in Sintered Nd-Fe-B Magnets: ab initio Study
The Role of Cu in Sintered Nd-Fe-B Magnets: ab initio Study
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DOI：
10.1109/tmag.2012.2202380
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发表时间：
2012-10
影响因子：
2.1
通讯作者：
X. B. Liu;Z. Altounian
中科院分区：
文献类型：
--
作者：
X. B. Liu;Z. Altounian
微量Cu的添加是通过改善烧结NdFeB磁体的显微组织来提高磁体磁性能的有效方法。Cu掺杂的效率取决于Cu在NdFeB磁体多相组织中的分布。为了理解和控制Cu的再分配，采用第一性原理密度泛函方法计算了Cu在Nd 2Fe 14 B（2：14：1）中取代Fe的位置偏好及其取代能.总能量计算结果表明，Cu在2：14：1中对Fe的取代能均为正值，表明Cu有避免进入2：14：1相的倾向。特别是，16 k1位（Fe）的Cu取代能值为55 meV/Cu/单位晶胞，这意味着Fe（16 k1位）被Cu以2：14：1取代可能发生在高温下（高于650 K）。预期非常少量的Cu（1.5at.%大约）在感应熔化烧结过程（高于1600 K）期间将以2：14：1溶解，而在烧结后退火过程期间从2：14：1晶粒耗尽到晶界区域。Cu在富Nd相中的再分布降低了富Nd相的熔点，促进了富Nd相沿着2：14：1相晶界的均匀分布，提高了烧结NdFeB的矫顽力。
Trace addition of Cu is an effective method to improve the coercivity of sintered NdFeB magnets via improving the microstructure. The efficiency of Cu doping depends on the distribution of Cu in the multi-phase microstructure of the NdFeB magnet. To understand and control the Cu redistribution, the site preference of Fe substitution by Cu in Nd2Fe14B (2:14:1) and their substitution energies have been calculated by a first-principles density functional method. The total energy calculations show that all the substitution energies of Fe by Cu in 2:14:1 are positive, indicating Cu tends to avoid entering 2:14:1 phase. In particular, the substitution energy of Cu at the 16k1 site (Fe) has a value of 55 meV/Cu per unit cell, implying the substitution of Fe (16k1 site) by Cu in 2:14:1 could occur at high temperature (above 650 K). It is expected that a very small amount of Cu (1.5 at.% or so) will dissolve in 2:14:1 during induction-melting sintering process (above 1600 K) while depleting from the 2:14:1 grains to the grain boundary region during the post-sinter annealing process. The redistribution of Cu in Nd-rich phase will lower its melting point and promote the homogeneous distribution of Nd-rich phase along the grain boundary of 2:14:1 phase, enhancing the coecivity in sintered NdFeB.