Optimization of the post-sintering annealing condition for the high Cu content Nd-Fe-B sintered magnet

• Published in: Journal of applied physics 2014-05, Vol.115 (17)
• Main Authors: Kim, Tae-Hoon, Lee, Seong-Rae, Woo Kim, Jin, Do Kim, Young, Kim, Hyo-Jun, Lee, Min-Woo, Jang, Tae-Suk
• Format: Article
• Language: English
• Subjects: Annealing; Coercivity; Copper; Dependence; Grain boundaries; Magnetic properties; Magnets; Neodymium; Phase transitions; Sintering; Transformation temperature
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4869157

We investigated the changes in microstructure and magnetic properties of Nd–Fe–B magnets as a function of Cu content (Cu addition in the range of 0.2–0.5 at. %). We have focused on the phase-transformation temperature of the Nd-rich phases in dependence of the Cu content. The coercivity of the magnets decreased (from 28.7 kOe to 27.1 kOe) on increasing Cu content under identical post-sintering annealing (PSA) conditions. The Cu-enriched C-Nd2O3 triple junction phase (TJP) and grain boundary phase (GBP) were observed in the 0.2 at. % Cu-containing magnet. However, in the 0.5 at. % Cu-containing magnet, the Cu-enriched TJP and GBP appeared in the form of the h-Nd2O3 phase that could be transformed into the C-Nd2O3 phase by a modified 1st-PSA temperature. The coercivity of the 0.5 at. % Cu-containing magnet was noticeably enhanced (from 27.1 kOe to 29.4 kOe).