Microstructure of single stage hot deformed anisotropic Nd–Fe–B magnets

Abstract

Single stage hot deformation (SSHD) process is an effective method to fabricate anisotropic magnet. In this study, the influences of particle size and hot press temperature on microstructure were discussed, respectively. Anisotropic magnetic properties are affected by SSHD process conditions through the changing the microstructure of the magnets. SEM investigation shows that, good magnetic properties related with suitable geometric shapes of the grains and their better alignment. Good alignment could be obtained when the particle size of raw material MQPA powders is between 45~100 µm and the SSHD magnet is made at 700 °C. When the deformation temperature is below the melting temperature of Nd rich phase, the platelet-shaped Nd 2 Fe 14 B grains could not be formed.

Mössbauer study of treated Nd2Fe14B

“…The most probable is the -Nd phase and the unstable NdO phase. The Nd 2 O 3 , Nd 1+ Fe 4 B 4 [1,11,12], and Nd 7 Fe 3 [13] phases could also be present in the intergranular material but in considerably lower amounts. As the total amount of the intergranular material was negligible relative to the main grain phase, no subspectra except the six sextets in the initial Nd 2 Fe 14 B spectrum were detected.…”