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

Abstract

The anisotropic (Nd,MM) 2(Fe,Co,Ni) 14B-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 Nd 2Fe 14B compound, while that of the sintering aid was MM 38.2Co 46.4Ni 15.4. 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 Nd 11.9MM 2.9Fe 73.9Co 3.3Ni 1.1B 6.9 made of 90 wt.% master alloy and 10 wt.% sintering aid. The two main phases, i.e. the (RE) 2(TM) 14B phase as the matrix and the rare-earth rich phase as the grain boundary phase, were identified in the specimens. No Nd 1.1Fe 4B 4 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°C.