The influence of carbon partial substituting Boron on structure and magnetic properties of the alloy Nd_(17)Fe_(76)(B_(1-)xCx)_7 has been studied by means of metallography. SEM differential thermal analysis (DTA). X-ray diffraction, electron probe microanalysis and pulsed high field measurements. Based on the results of the structure and basic magnetic properties of casting samples, it was found that the grain size and the lattice constant c of matrix decrease, but the lattice constant a is nearly stable; B-rich phase becomes less, but α-Fe grows more as the increase of carbon content. To the samples with X < 0.9, carbon can replace Boron continuously to form stable hard magnetic phase Nd_2Fe_(14)(B, C). However, the matrix of other two samples with X = 0.9 and X = 1 consists of Nd_2Fe_(17)C_x and α-Fe. he eutectic temperature Te is almost the same but the curie temperature Tc decrease as increase of carbon. The saturation magnetization Ms decreases slightly but the anistropy field Ha increases effectively with carbon content. The molecular field theory has been used to explain above results successfully The best method of technology for C-containing magnets has been suggested. A viewpoint has been proposed that the mechanism of grinding for C-containing magnets is brittle fracture mainly along grain boundary. The grinding time depends on hardness and grain size of matrix and grain boundary phase of which the increase of hardness is the main factor. Nd_(17)Fe_(76)(B_(1-)xCx)_7 magnets have been prepaired by sintering method. The relationship between Ha and iHc has been discussed. It was proved furtherly that the coactivity iHc depends on both Ha and the microstructure of magnets, and that the reason of iHc decreasing with carbon is disadvantage microstructure. Finally the coercivity mechanism of the magnet has been discussed according to above experimental results.
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