Production of (Nd,MM)2(Fe,Co,Ni)14B-type sintered magnets using a binary powder blending technique

The anisotropic (Nd,MM)(2)(Fe,Co,Ni)(14)B-type magnets were produced using the binary alloy sintering method (MM denotes a Misch-metal). The composition of the master alloy was close to stoichiometric Nd2Fe14B compound, while that of the sintering aid was MM38.2CO46.4Ni15.4. The microstructures of sintered magnets were investigated using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray detector (EDX). X-ray diffractometry (XRD) was also employed for phase analysis. The optimum magnetic properties were obtained for a composition of Nd11.9MM2.9Fe73.9Co3.3Ni1.1B6.9 made of 90 wt.% master alloy and 10 wt.% sintering aid. The two main phases, i.e. the (RE)(2)(TM)(14)B phase as the matrix and the rare-earth rich phase as the grain boundary phase, were identified in the specimens. No Nd1.1Fe4B4 boride phase was observed in these samples, while there was some Fe-rich phase in the specimens with lower amount of sintering aid. The permanent magnet properties of the specimen in the optimum condition were as follows: B-r=11.2 kG, H-cj = 11.5 kOe and (BH)(max) = 32 MGOe with a Curie temperature of 351 degrees C. (C) 2000 Published by Elsevier Science S.A. All rights reserved.