Abstract
We have investigated the changes in the magnetic, phase-transformation and microstructural properties of Nd-Fe-B sintered magnets as a function of Cu content (0.2-0.5 at.%). The coercivity decreased (28.7 → 27.1 kOe) with increasing Cu content without changing the remanence of the magnets under the normal post-sintering annealing (PSA) conditions. Phase-transformation temperature changes of the magnet were observed as the Cu content of the magnet was increased. In the 0.2 at.% Cu magnet, the triple junction phase (TJP) and grain boundary phase (GBP), composed of the Cu-enriched C-Nd2O 3 phase, were formed. However, in the 0.5 at.% Cu magnet, the TJP and GBP were composed of the h-Nd2O3 phase. By considering the dependence of Cu content on the phase transformation, we have modified the 1st-PSA temperature to recover the coercivity. Through our newly established PSA conditions, the TJP and GBP in the 0.5 at.% Cu magnet were formed as the C-Nd2O3 phase. As a result, the coercivity of the magnet was noticeably enhanced (27.1 → 29.4 kOe). The reasons for the coercivity deterioration in the high-Cu-content magnet were clarified. The detailed mechanism of the microstructural and magnetic property improvements induced by the modified 1st-PSA condition is discussed. The critical role of Cu in the microstructural changes of Nd-rich TJP and GBP during the PSA is also analyzed based on these results.
Original language | English |
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Pages (from-to) | 12-21 |
Number of pages | 10 |
Journal | Acta Materialia |
Volume | 66 |
DOIs | |
Publication status | Published - 2014 Mar |
Bibliographical note
Funding Information:This research was supported by the Technology Innovation Program funded by the Ministry of Knowledge Economy (MKE, Korea) (No. 10043780) and the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2011-0007200), Republic of Korea.
Keywords
- Cu content
- Nd-Fe-B sintered magnets
- Nd-rich phase
- Phase-transformation temperature
- Post-sintering annealing
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Polymers and Plastics
- Metals and Alloys