The Exploration Of Nd-Fe-B Permanent Magnetic Materials

In this thesis, Nd-Fe-B permanent magnets are prepared by the means of vacuum sintering process. Otherwise, the influence of different additives and texture on performance are respectively studied.The samples are prepared as the element proportion (Pr-Nd)_33.5Fe_64.85B_1.15A_10.5 by smelting and casting, pneumatic milling for powder, doping and mixing sufficiently, orientation and forming, vacuum sintering, mechanical treatment and etc. The experimental results shows: (1) In the same progress of sintering, the coercivity of sintering magnet is firstly increased and then decreased with the increasing of A1N addition amount, whose maximum occurs in the point of 0.55%. but the remnant magnetism and magnetic energy product declined with its increasing. (2) The addition of Cu makes the same trend of coercivity with AIN, but the maximum appears in the point of 0.3%. (3) The maximum working temperature Tm of Nd-Fe-B has been computed by the theoretical formula and experimental parameter, through which the theoretical value of coercivity also has been computed indirectly.The crystal texture of magnetic body inevitably exists some difference by molding in different magnetic fields, which reflects the regular changes of mechanical properties in macro. As a result that Nd-Fe-B material belongs to the brittle material and has the high hardness, its mechanical properties may be improved by changing its crystal texture. The experimental result shows: (1) In different magnetic fields, the intensity of X-Ray diffraction peak of different crystal face perpendicular to the c-axis direction changes, in which the changes of (004), (105), (006) and (008) faces are obvious. (2) The magnetic properties of Nd-Fe-B change with different orientation of samples, in which the remanence falls, but the coercivity remain changeless.(3)The hardness of sample decreases with the increasing of orientation intensity, which shows some relationship between crystal texture and mechanical properties.This paper adopt Hitachi S-3400N SEM, DGN-3 DC Magnetic Testing Instrumentation, BDX3200 XRD, HV-120 Vickers Hardness, Hv-1 Micro-hardness to test the crystal phase, magnetic properties, orientation degree and hardness. The results show that the addition of AIN and Cu makes different effects on the coercivity and maximum working temperature of Nd-Fe-B permanent-magnetic material. In addition, the hardness and remnant magnetism of magnetic body exist some relationship with the crystal texture.