Production of fully dense Nd-Fe-B magnets by hot pressing technique using semi-processed HDDR powders

Anistropic fully dense Nd-Fe-B magnets can be produced by compacting the HDDR-processed powder under an orienting magnetic field, and then by hot pressing the green compacts. In this study, we investigated orienting field dependence of the magnetic properties in the hot pressed magnets made from the Nd12.7Dy0.3Fe64.3Co16.0B6.2Zr0.1Ga0.4 powder in the different stages of the HDDR process. It was found that the semi-processed HDDR powder, in which the recombination reaction of the decomposed phases is not completed, can be more highly oriented in the applied magnetic fields less than 1190 kA/m in comparison with the fully HDDR-processed powder. The magnet with Bt = 1.13 T, HcJ = 1280 kA/m, and (BH)max = 230 kJ/m3 can be obtained by dehydrogenating the compact of the semi-processed powder before the hot pressing.