Prokofev Pavel A, Kolchugina Natalia B, Skotnicova Katerina, Burkhanov Gennady S, Kursa Miroslav, Zheleznyi Mark V, Dormidontov Nikolay A, Cegan Tomas, Bakulina Anna S, Koshkidko Yurii S, Smetana Bedřich
Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, 119334 Moscow, Russia.
Joint Stock Company "Spetsmagnit", 127238 Moscow, Russia.
Materials (Basel). 2020 Jul 8;13(14):3049. doi: 10.3390/ma13143049.
The wide application of Nd-Fe-B permanent magnets, in addition to rare-earth metal resource constraints, creates the necessity of the development of efficient technologies for recycling sintered Nd-Fe-B permanent magnets. In the present study, a magnet-to-magnet recycling process is considered. As starting materials, magnets of different grades were used, which were processed by hydrogen decrepitation and blending the powder with NdH. Composition inhomogeneity in the NdFeB-based magnetic phase grains in the recycled magnets and the existence of a core-shell structure consisting of a Nd-rich (Dy-depleted) core and Nd-depleted (Dy-enriched) shell are demonstrated. The formation of this structure results from the grain boundary diffusion process of Dy that occurs during the sintering of magnets prepared from a mixture of Dy-free (N42) and Dy-containing magnets. The increase in the coercive force of the N42 magnet was shown to be 52%. The simultaneous retention of the remanence, and even its increase, were observed and explained by the improved isolation of the main magnetic phase grains as well as their alignment.
除了稀土金属资源限制外，钕铁硼永磁体的广泛应用使得开发高效的烧结钕铁硼永磁体回收技术成为必要。在本研究中，考虑了磁体对磁体的回收工艺。使用不同等级的磁体作为起始材料，通过氢破碎处理并将粉末与氢化钕混合。结果表明，回收磁体中钕铁硼基磁相晶粒存在成分不均匀性，并且存在由富钕（贫镝）核心和贫钕（富镝）外壳组成的核壳结构。这种结构的形成是由于在由无镝（N42）磁体和含镝磁体的混合物制备的磁体烧结过程中发生的镝的晶界扩散过程。结果表明，N42磁体的矫顽力提高了52%。剩磁得以保持，甚至有所增加，这是由于主磁相晶粒的隔离得到改善及其取向得到改善所致。
