Microstructural evolution of triple junction and grain boundary phases of a Nd-Fe-B sintered magnet by post-sintering annealing

Tae Hoon Kim, Seong Rae Lee, Dong Hwan Kim, Seok Nam-Kung, Tae Suk Jang

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17 Citations (Scopus)

Abstract

The microstructural evolution of Nd-rich grain boundary phases (GBP) in connection with triple junction phases (TJP) during post-sintering annealing (PSA) was investigated. The Cu-rich TJP in the as-sintered sample was mostly a fcc-NdO phase but the GBP were a mixture of h-Nd2O3 and Nd phases. The fcc-NdO of the TJP in the as-sintered state gradually transformed to h-Nd2O3 during the first and the second PSA steps. However, it transformed to a C-Nd2O3 phase as both a massive form such as TJP and a thin GBP after the modified second PSA step. This suggests that the mechanism for the formation of metastable C-Nd 2O3 may not be solely the interface energy. In contrast, the mixture of h-Nd2O3 and Nd of the GBP in the as-sintered state gradually transformed to C-Nd2O3 which is embedded in the amorphous matrix as the PSA goes from the first to second or modified second PSA step. The formation of the C-Nd2O3 GBP with an amorphous phase is the main factor for increasing the coercivity (from 21.8 to 30.4 kOe) after the second or modified second PSA step.

Original languageEnglish
Article number07A703
JournalJournal of Applied Physics
Volume109
Issue number7
DOIs
Publication statusPublished - 2011 Apr 1

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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