[T16] Hard Magnetic Materials

[14E-T16-01] High-Performance Nd-Saving Hot-Deformed Permanent Magnets

*J. Lee¹, T. Kim¹, H. Cha¹, G. Kim¹, J. Yu¹ (1.Korea Institute of Materials Science, Korea)

キーワード：rare-earth magnets, Nd-saving, amorphous, hot-deformation

Current challenge in Nd-Fe-B permanent magnets is to achieve high-performance Na-saving magnets. Nd is expensive and very unstable in supply and demand, but it is essential for realizing the high performance in rare earth permanent magnets. To realize the Nd-saving technology, the content of Nd should be reduced by replacing it with inexpensive Ce. However, until now, it has not been possible to prevent the deterioration of the magnetic properties of the magnet as the Ce content increases due to the inferior intrinsic magnetic properties of Ce₂Fe₁₄B compared to Nd₂Fe₁₄B. In addition, it is recently reported that Ce-segregated ReFe₂ secondary phases are formed, which significantly deteriorate the microstructure and magnetic properties in the Nd-saving hot-deformed magnet. On the other hand, it has been reported that the deterioration of magnetic properties due to Ce substitution could be largely suppressed by developing a dual main phase structure in Nd-Fe-B sintered magnets. The short-range exchange coupling and long-range magnetostatic interaction induced by the peculiar chemical heterogeneity of dual main phase magnets are believed to be a key factor for improving coercivity and remanence of Nd-Ce-Fe-B sintered magnets. In this study, the limit of the hard magnetic properties of the Ce-substituted magnets was successfully surpassed by the hot-deformation using amorphous precursors that contain no (Nd, Ce)Fe₂ secondary phases. In addition, we also developed the dual main phase Nd-Ce-Fe-B hot-deformed magnets using two different amorphous melt-spun precursors with different compositions.