Microstructure and magnetic properties of directly quenched Nd₂Fe₁₄B/α-Fe nanocomposite materials at different temperatures

SHENG Hong-chao(盛洪超)^{1, 2, 3}, ZENG Xie-rong(曾夑榕)^{1, 2, 3}, JIN Chao-xiang(靳朝相)^{1, 2, 3}, QIAN Hai-xia(钱海霞)^{1, 2, 3}

(1. Shenzhen Key Laboratory of Special Functional Materials (Shenzhen University), Shenzhen 518060, China;
2. College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, China;
3. Shenzhen Engineering Laboratory for Advanced Technology of Ceramics
(Shenzhen University), Shenzhen 518060, China)

Abstract:Directly quenched Nd_9.5Fe₈₁Zr₃B_6.5 nanocomposite permanent magnets were prepared under different melt treatment conditions, i.e., the melt temperature was varied prior to ejection onto the quenching wheel. The effect of quenching temperature on the microstructure and magnetic properties of the alloys was studied by X-ray diffractometry, transmission electron microscopy and magnetization measurements. It is found that a finer and more uniform microstructure can be obtained directly from the melt quenched at lower temperature. With increasing initial quenching temperature, the optimal quenching speed decreases and the microstructure of the ribbons becomes coarser and more irregular. As a result, the magnetic properties of the alloys are deteriorated. It is believed that the break of the pre-existing Nd₂Fe₁₄B clusters and decrease in number of the developing nuclei of Nd₂Fe₁₄B phase with increase in quenching temperature may be the causes for the change of the microstructure and the magnetic properties of the ribbons.

Key words:microstructure; nanocomposite magnet; quenching temperature