Study on rheological behaviors of the binder for producing anisotropic NdFeB bonded magnets

Anisotropic NdFeB bonded magnet was prepared by warm compaction technique. Effect of the rheological behaviors of bisphenol A type epoxy on the magnetic properties, degree of alignment as well as density of the magnets was studied. Rheological behaviors of the epoxy and the magnetic properties of the magnets were investigated by means of rheometer and B-H loop-line instrument, respectively. Microstructure of the magnets was observed by using scanning electron microscope (SEM). It is shown that the optimum processing temperature of the epoxy for warm compaction is 120°C, at which the epoxy can keep low viscosity and good fluidity for about 2 minutes. Under this status, the densification and aligning process of the magnetic powders along with the magnetic field could be assisted well, and the degree of alignment and the density of the magnet rose remarkably. As a result, the bonded magnet possesses ideal magnetic properties.