Magnetic properties and microstructure of magnesium-doped Nd-Fe-B magnets

Abstract

A number of Nd15 Fe79−x Mgx B6 magnets with x up to 0.41 and pseudoternary Nd2(Fe1−yMgy)14B compounds with y up to 0.081 have been prepared by conventional powder metallurgy processes. Magnetic measurements indicate that for the magnet alloys i Hc increases as x increases up to 0.25 without a loss in Br, hence the (BH)max values are slightly enhanced. The maximum increase in i Hc is about 15% for x=0.25. Extensive Mg-rich precipitates inside the Nd-rich phase have been observed by electron probe microanalysis (EPMA). Higher Mg intensity at grain boundaries is also detected by EPMA. The reasons for the i Hc increase might be the grain boundary cleaning ability of Mg dopant. For the pseudoternary compounds, the anisotropy field HA is found to increase only slightly due to Mg doping while TC remains practically unchanged.