Two-Step Sintering of Nd-Fe-B Powder

Abstract

Sintered Nd-Fe-B magnets have been wildly used due to their excellent magnetic propcrties. However, heterogeneous microstructurc of Nd- Fe-B magnet is an important factor limiting their magnetic property. Therefore, modifying a sintering process has been an important method for better homogeneous microstructure.ln this study, Nd-Fe-B powder was fabricated by Strip-casting and jet milling. The powder was compacted in a magnetic field. After that, the green compact was sintered at temperature between 1050oC and 1150oC as first-step, then, second- step was sintered at temperature between 900oC and IOOOoC. Two-step process was employed for the sintering of Nd-Fe-B powder to obtain homogeneous grain size in bulk part. Densification over 99% could be obtained by the two-step sintering of Nd-Fe-B powder wilh 5 um in Nd2Fe14B phase and the Nd-rich phase was homogeneously distributed. Moreover, the two-step sintering process led to uniform grain size distribution with the improvement of magnetic properlies.