Homogeneity of Hcj in sintered bulk Nd-Fe-B magnets

High performance magnets not only have high magnetic properties, but also have good homogeneity. The homogeneous of Nd14.2DyAl0.8Cu0.1B6.2Febal. bulk magnets was studied. The sizes of the samples produced by conventional sintering process were 53 x 50.5 x 25.3/40.2/50.4/61.0 mm. The magnetic character and microstructure of the samples were determined by NIM-10000H hysteresigraph, optical metaloscope, and SEM respectively. The results show that the H-cj reduces with increasing C content at the same process parameters. And the H-cj shows dependence not only on the aged ing processing but also on the size of the bulk and loading capacity etc. The H-cj increases with prolonging ageing time and the ageing time should be different with different size of the bulk. With the increase of the loading capacity, the H-cj reduces promptly and is very inhomogeneous. The microstructure of the samples shows that the grain of the hard magnetic phase is finer and the neodymium-rich boundary is distributed homogeneously with prolonging ageing time. And so is the sample in a small amount of the bulks.