Research Of Structure And Properties Of Sintered Nd-Fe-B Permanent Magnets By Strip Casting And Hybrid Of Two Alloys

In this paper, The methods of manufacturing sintered Nd-Fe-B permanent magnets by combination of SC(strip casting) and Hybrid of two alloys have been investigated. The microstructure, magnetic properties and mechanics capability of the Nd-Fe-B permanent magnets were studied. The main results are as follows:1. Compared with traditional ingot, the microstructure of the casting strip is obviously optimized. The crystal grains are small, pillar-like grains are clear, the Nd-rich phase is uniformly and thinly distributed around the main phase. Nd-Fe-B cast strip has ideal microstructure to produce magnets with high magnetic properties. The texture formation and its orientation has a big change after the strip cast process. The texture orientation is along with the <0,0,L> direction, which might be due to the restriction distortion perpendicular to the connection plane between the strip and the wheel. Behavior of hydrogen absorption has relationship with cast strip composition. The temperature of hydrogen absorb reduces with the increase of the rare-earth element contents. However, for Dy replacement, the result is contrast completely.2. Base on the theory of the strip casting, component of Nd-Fe-B permanent magnets was optimized, and the Nd-Fe-B permanent mangets were produced through hybrid of two alloys. Through analysing the effection of element change in boundary phase on the magnets microstructure, we conclude that: (1) Nd-rich phase change magnets performance by the quantity of Nd addition and the effect of changing the wetness of liquid phase in sinterd process. (2) The compound Nd₂Fe₁₄B formed through diffusion of boundary element has different crystalline anisotropy and saturation intension of magnetic polarization. Thereby, the magnetic performance of the magnets bulk is changed.3. The impact resistance of the sintered Nd-Fe-B permanent magnets was investigated by the fracture behavior. The substitution of Pr for Nd by diffusion lead to boundary phase distribution optimized and the impact resistance has been improved. The substitution of Dy for Nd, however, produces the hole and damages the impact resistance.4. The annealing processes affect greatly both the magnetic properties and mechanical properties. In the low temperature annealing process, the bending strength and the intrinsic coercivity has been improved. As compared with the as-sintered magnets, the grains turn smooth ,and the R-rich phase regions in magnets tend to be homogenous. In low temperature annealing process, the resistant of sintered Nd-Fe-B permanent magnets achieved maximum while Heat treating at Eutectic reaction temperature.